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1. New Delhi is an urban district of Delhi which serves as the capital of India and seat of all three branches of the Government of India. As of 2011, population of 21.75 million.

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3. According to the report, air pollution will cause around 7 million premature deaths globally next year and have a major economic impact.

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Versión en Español
The AQI is an index for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be a concern for you. The AQI focuses on health effects you may experience within a few hours or days after breathing polluted air. EPA calculates the AQI for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide. For each of these pollutants, EPA has established national air quality standards to protect public health .Ground-level ozone and airborne particles are the two pollutants that pose the greatest threat to human health in this country.

How Does the AQI Work?

Think of the AQI as a yardstick that runs from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health concern. For example, an AQI value of 50 represents good air quality with little potential to affect public health, while an AQI value over 300 represents hazardous air quality.

An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EPA has set to protect public health. AQI values below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is considered to be unhealthy-at first for certain sensitive groups of people, then for everyone as AQI values get higher.

Understanding the AQI

The purpose of the AQI is to help you understand what local air quality means to your health. To make it easier to understand, the AQI is divided into six categories:

Note: Values above 500 are considered Beyond the AQI. Follow recommendations for the Hazardous category. Additional information on reducing exposure to extremely high levels of particle pollution is available here.

Each category corresponds to a different level of health concern. The six levels of health concern and what they mean are:

"Good" AQI is 0 to 50. Air quality is considered satisfactory, and air pollution poses little or no risk.

"Moderate" AQI is 51 to 100. Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people. For example, people who are unusually sensitive to ozone may experience respiratory symptoms.

"Unhealthy for Sensitive Groups" AQI is 101 to 150. Although general public is not likely to be affected at this AQI range, people with lung disease, older adults and children are at a greater risk from exposure to ozone, whereas persons with heart and lung disease, older adults and children are at greater risk from the presence of particles in the air.

"Unhealthy" AQI is 151 to 200. Everyone may begin to experience some adverse health effects, and members of the sensitive groups may experience more serious effects.

"Very Unhealthy" AQI is 201 to 300. This would trigger a health alert signifying that everyone may experience more serious health effects.

"Hazardous" AQI greater than 300. This would trigger a health warnings of emergency conditions. The entire population is more likely to be affected.

AQI colors

EPA has assigned a specific color to each AQI category to make it easier for people to understand quickly whether air pollution is reaching unhealthy levels in their communities. For example, the color orange means that conditions are "unhealthy for sensitive groups," while red means that conditions may be "unhealthy for everyone," and so on.

Air Quality Index Levels of Health Concern

Numerical
Value

Meaning

Note: Values above 500 are considered Beyond the AQI. Follow recommendations for the "Hazardous category." Additional information on reducing exposure to extremely high levels of particle pollution is available here.

This page was last updated on Tuesday, June 18, 2019

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Versión en Español The AQI is an index for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be a concern for you. The AQI focuses on health effects you may experience within a few hours or days after breathing polluted air.

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4. "...evidence suggests that air pollution contributes to the large global burden of respiratory and allergic diseases..."

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Abstract

Mounting evidence suggests that air pollution contributes to the large global burden of respiratory and allergic diseases including asthma, chronic obstructive pulmonary disease, pneumonia and possibly tuberculosis. Although associations between air pollution and respiratory disease are complex, recent epidemiologic studies have led to an increased recognition of the emerging importance of traffic-related air pollution in both developed and less-developed countries, as well as the continued importance of emissions from domestic fires burning biomass fuels primarily in the less-developed world. Emissions from these sources lead to personal exposures to complex mixtures of air pollutants that change rapidly in space and time due to varying emission rates, distances from source, ventilation rates, and other factors. Although the high degree of variability in personal exposure to pollutants from these sources remains a challenge, newer methods for measuring and modeling these exposures are beginning to unravel complex associations with asthma and other respiratory disease. These studies indicate that air pollution from these sources is a major preventable cause of increased incidence and exacerbation of respiratory disease. Physicians can help to reduce the risk of adverse respiratory effects of exposure to biomass and traffic air pollutants by promoting awareness and supporting individual and community-level interventions.

Keywords: biomass, traffic, COPD, asthma, air pollutants, particulate matter

Introduction

Worldwide increases in rates of asthma and COPD over the past several decades have motivated intensive investigation of the role of environmental factors, including air pollution, in their causation. Recent research also suggests that air pollution contributes to the substantial worldwide burden of disease from acute lower respiratory infections and possibly tuberculosis. While the health effects of air pollution have been an international public health concern since at least the 1950's, recent research has heightened the focus on two broad sources of air pollution: biomass fuels (BMF) and motor vehicles. Understanding of the health effects of BMF and traffic-related air pollution (TRAP) has lagged behind that of ambient air pollution, at least in part due to challenges in estimating highly-variable individual exposure from these widespread, but very localized, air pollution sources.

Of course, air pollution is only one of many environmental (non-genetic) factors for which a causative role in exacerbation or incidence of complex respiratory diseases has been suggested. Indeed, based on ecological analyses from the International Study of Asthma and Allergies in Childhood (ISAAC), generally less-polluted developed countries (DCs) have much higher rates of asthma than many countries with higher levels of air pollution. However, studies with individual-level analyses that control for potential confounding have demonstrated associations between air pollutants, including TRAP, and asthma exacerbation, as well as possible links to increased asthma incidence. Additional evidence suggests that exposure to TRAP is correlated with the rising rates of allergic respiratory disease. Although tobacco smoke is clearly the dominant cause of COPD worldwide, BMF smoke is now recognized as a major cause of COPD, especially among women in less developed countries (LDCs). Current evidence also indicates that BMF smoke plays a causative role in mortality from lower respiratory infections among children living in homes where BMF is used. The effects of indoor air exposures and individual ambient pollutants on asthma have recently been discussed in this forum. Here, we emphasize the growing body of recent research pertaining to the relationship between respiratory health effects and exposure to TRAP and biomass air pollution. For recent reviews of the respiratory health effects of traffic exposures see Kelly and Fussell (2011) and Salam et al. (2008), and for BMF see Torres-Duque C (2008), Balmes (2010), Fullerton (2008).

Exposures to Biomass and Traffic Pollutants

Exposures to BMF smoke and TRAP are widespread. Domestic fires burning biomass (wood, charcoal, dung, crop residues, and other raw plant materials) for cooking and/or heating remain the most pervasive and important source of exposure to air pollution for much of humanity. About 2.4 billion people live in households in which BMF is the primary cooking and/or heating fuel, with more than 90% of individuals in rural areas of LDCs using BMF. Exposures are often exacerbated by use of open fires or traditional stove designs that lack flues or hoods to exhaust emissions away from the living area.

While stationary industrial "smokestacks" continue to be a major source of outdoor air pollution from the burning of fossil fuels throughout the world, TRAP from motor vehicles are a growing concern in both DCs and LDCs. Regulation of ambient (widespread, regional) 'criteria' pollutants in the US and other DCs has resulted in relatively effective stationary and mobile source controls. However, an increased number of vehicles and vehicle-miles-driven has lessened the impact of vehicle emissions controls. At the same time, heavy industry has moved to LDCs, resulting in a higher relative contribution from mobile sources in DCs, while in LDCs both total stationary and mobile source emissions have been increasing. Most of the worldwide growth in fleets of gasoline and diesel vehicles is occurring in LDCs. As discussed below, in addition to making large contributions to background ambient air pollution, mobile sources may dominate exposures near roadways in urban areas, where a growing proportion of the world's population lives.

Although one is rooted in longstanding cultural practices and the other arises from modern economic development, emissions from domestic fires and from motor vehicles have similarities in composition, toxicity, and exposure characteristics. Complex aerosol emissions from use of BMF share many components with TRAP and other outdoor PM, including particulate matter, carbon monoxide, nitrogen oxides, and scores of toxic organic compounds, such as formaldehyde, acrolein, and polynuclear aromatic hydrocarbons (PAHs). However, the physical and chemical characteristics of both BMF smoke and TRAP can vary substantially depending on the type of fuel burned and combustion conditions.

Based on robust epidemiological associations between ambient particulate matter (PM) and respiratory and cardiovascular health effects, much attention has focused on the PM component of BMF and motor vehicle emissions. PM of respirable size is classified by size fractions based on aerodynamic diameter. Ultrafine PM (UFP) with diameters ≤ 0.1 µm (PM0.1) is a major component of emissions near fires and tailpipes, but in seconds to minutes accumulates into somewhat larger "fine PM," or PM 2.5 with diameters ≤ 2.5 µm, within short distances from the point of release. PM ₁₀, with diameters ≤ 10 µm, consists of PM 2.5 and larger particles of mainly crustal or biological origin, including many aeroallergens. Based on epidemiological and laboratory studies, PM 2.5 appears to be more potent for respiratory and cardiovascular disease effects compared to PM10. According to the "ultrafine hypothesis," ultrafine PM may be still more toxic due to increased surface area and other characteristics. Although they contribute little to the mass concentration of PM due to their small size, ultrafine particles emitted by combustion dominate the particle number concentrations near these sources.

In contrast to large-scale industrial sources of air pollution, the sources of biomass and traffic emissions tend to be in close proximity to individual "receptors." Biomass emissions occur primarily indoors, where women and children are most highly exposed during cooking and other domestic activities. Exposures are exacerbated by reduced ventilation in homes where biomass in used, or under conditions in which vehicle emissions may be concentrated as in urban street canyons or tunnels. Concentrations of TRAP have steep gradients near roadways, with heightened exposure to individuals living, attending school, or working near major roads in urban areas, and return of TRAP to background levels within several hundred meters away from roadways. For both BMF emissions and TRAP, time-activity patterns are a critical determinant of exposure. Household members who cook have high peak exposures, as when standing over the fire, as well as high time-averaged exposures to biomass pollutants. Individuals living and working in urban areas may have a substantial part of their daily air polllutant exposure during usually relatively brief commuting times on roadways where TRAP are concentrated. Substantial differences in TRAP concentrations and in inhaled doses as a consequence of travel mode, biking vs car vs bus, have been demonstrated, with bicyclists generally having the highest doses and electric bus riders the lowest. Moreover, with distance and time away from sources, both BMF and vehicle emissions undergo complex "aging" processes that include oxidation, other chemical reactions and physical processes that alter exposure and toxic properties in ways that are not fully understood.

The levels of BMF air pollutants measured in homes are typically far higher than ambient air pollutants, but they have received less attention from the international research community. Concentrations of PM and other air pollutants in indoor air during biomass burning can be orders of magnitude higher than levels that occur in ambient air in developed cities. Levels of PM ₁₀ in homes using BMF often exceed several thousand µg/m ³ , compared to the EPA 24-hr ambient air quality standard of 150 µg/m ³ PM ₁₀ and the WHO guideline of 50 µg/m ³ PM ₁₀.. Little data is available on PM 2.5 and UFP indoors from BMF burning. The near-roadway microenvironment is mainly impacted by freshly-emitted UFPs and gas-phase compounds such as carbon monoxide, nitrogen oxides, and VOC's although resuspended road dust, mainly in the "coarse" mode of the PM ₁₀ fraction, may be an important exposure.

The uneven distributions of exposure to BMF smoke and TRAP leads to uneven distribution of health risks, and environmental justice considerations at local, regional, national, and global scales. There are age, gender, and socioeconomic differences in who is most exposed and most vulnerable to the health effects of BMF emissions and TRAP. Exposure to BMF smoke is greatest among women and among young children who may be carried on mother's back during cooking activities, or spend more time indoors with mother. BMFs that are least expensive and more affordable for impoverished households also burn less efficiently, increasing pollutant emissions. TRAP exposures are concentrated in areas of greater traffic density, which, at least in the US, tend to be inner city communities of lower socioeconomic status with a higher burden of environmental contamination/impacts.

Epidemiology of Health Effects of BMF and TRAP

Individual exposure assessment has been a major challenge for epidemiological studies of both BMF and TRAP, in contrast to studies of ambient air pollution, in which assigning personal exposure based on central air monitoring data has had demonstrated utility. Few epidemiologic studies of respiratory effects of BMF smoke have measured exposure, relying instead on self-report of fuel use, despite evidence for wide variation in exposure depending on combustion and ventilation conditions and time-activity patterns. More recent studies, including controlled trials of stove interventions, have begun to measure exposure. As described above, the spatial and temporal distributions of urban air pollutants are characterized by significant variability with steep gradients in intensity near sources. Thus, the use of land use regression and other techniques for modeling microenvironmental exposures for various particle and gas pollutants has become widespread and is featured in a number of the newer studies of TRAP to be described below. Land-use regression (LUR) uses the monitored levels of the pollutant of interest as the dependent variable and variables such as meteorology, traffic, topography, building shapes and sizes, and other geographic variables as the independent variables in a multivariate regression model. Levels of pollution may then be predicted for any other geographic locations, such as residences or schools, using the parameter estimates derived from the regression model. A limitation is that LUR often captures only one time period, and may miss prior or neonatal exposures, however some studies have overcome this. Further details are available in recent reviews.

The most firmly established health effects of BMF emissions are acute lower respiratory infections in children and COPD in adults. While studies of ambient pollution effects have repeatedly demonstrated increased cardiovascular and respiratory morbidity and mortality for a variety of outcomes, those which have studied TRAP specifically have largely focused on asthma and related phenomena, with some investigations of allergy. The World Health Organization has estimated that BMF smoke exposure is responsible for about 1.5 million premature deaths per year, and a global burden of disease of approximately 2.5% of all healthy life-years lost. Most of this burden of disease is due to respiratory infections, mainly among children less than 5 years of age, and COPD among adult women. Several case-control and cross-sectional studies have evaluated associations between use of biomass fuels and prevalence of asthma with equivocal results among children and women. Other studies have found strong associations between BMF smoke and COPD among non-smoking women. Important new studies, discussed below, have strengthened the link between TRAP and asthma incidence in children, incidence in adults and severity in adults.

BMF and COPD

Given that cigarette smoke is a type of biomass smoke, a causal association between exposure to BMF smoke and COPD would not be surprising. Three recent meta-analyses have evaluated associations between BMF smoke and COPD. In a systematic review and meta-analysis of 23 studies, Kurmi et al found that exposure to all types of BMF smoke was consistently associated with COPD with risk more than doubled, with greater risk suggested for woodsmoke compared to other fuels. Hu et al analyzed 15 studies and found that BMF smoke was associated with increased risk of COPD among both women and men, and in both Asian and non-Asian populations. In a meta-analysis of 6 studies that evaluated COPD among women using biomass compared to alternative fuels, Po et al also found a statistically significant pooled estimate of greater than 2-fold increased risk. In another 6 studies that assessed chronic bronchitis, the pooled risk estimate was also greater than 2-fold. However, most studies have lacked direct exposure measurements, none have described a dose-response relationship, and estimated effect sizes have varied widely. This variation may be due to heterogeneity in fuel types and conditions of use, as well as in study design and differences in control of confounders such as exposure to mainstream or second-hand cigarette smoke, occupational exposures, socioeconomic factors, and changes in fuel use over time. In a study of 841 nonsmoking women in Mexico that was notable for objective exposure and outcome measurements, Regalado et al found that peak PM ₁₀ over 2,600 µg/m3 among those using biomass fuels was related to small, but significant, reductions in FEV1 (81 ml), FVC (122 ml), and FEV1% predicted (4.7) compared to women who cooked with gas. In an accompanying editorial, Jaakola noted that these effects were comparable to the estimates from environmental tobacco smoke exposure in adults. Cigarette smoking rates are relatively low in most LDCs, especially among women. Among women living in rural Turkey, the fraction of COPD attributed to exposures to BMF smoke was 23% after adjusting for possible confounders.

TRAP AND COPD

A number of studies have established that children living in more polluted areas,have reduced lung growth compared to those living in cleaner areas, and that moving from a more polluted to a cleaner area demonstrates improved growth. Similar findings for lung function have been reported in adults, as well as a limited data base of studies documenting an association between ambient air pollutants and objectively defined COPD.

Most recently, a 35 year prospective study of over 57,000 Danes, used individual modeled assignments of traffic pollution and extensive control of confounders, with the end point of first hospital admission for COPD. This outcome was associated with chronic NO ₂ exposure (HR=1.08, 1.02-1.14) with a stronger association in asthmatics. This is the first longitudinal study of COPD with hard outcomes in association with modeled TRAP exposures, and seems to confirm the previous findings of cross-sectional studies that TRAP is likely to be a cause of COPD.

TRAP and Asthma Overview

Studies have long shown that asthma can be exacerbated, often measured as visits to emergency rooms, on days with higher levels of ozone and other pollutants. More complex cohort study designs have been required to understand whether or not traffic-related pollutants play a role in the genesis, or causation, of asthma. To date all such investigations in a non-occupational setting have related to chronic, rather than acute, air pollution exposures. More sophisticated designs have been used in recent years and this part of the review will focus on those reported since 2009.

TRAP and Childhood Asthma

Initial studies of air pollution and asthma examined associations in children, looking first at exacerbations and more recently, through cohort studies, at incidence. Initial reports of incidence in children were variable in their results. Investigators interpreted these inconsistencies to result from misclassification of pollution exposure to the individual cases, likely due to reliance on central or regional air monitoring stations that do not reflect urban microgeographies. Subsequent studies using LUR or dispersion modeling produced significant associations in both children. and adults, with refinement of exposure through use of LUR techniques yielding larger and significant associations with chronic pollution exposure.

Two recent studies, one a birth cohort, add substantially to our confidence that TRAP exposure of young childen contributes to the development of asthma. Both used sophisticated exposure assessment in the form of LUR or a related technique to study the association between childhood asthma and TRAP exposure at home and/or school. Increased risk of for childhood asthma incidence demonstrated significant increases of 26% up to 51%, with good control of relevant confounders. Interestingly the birth cohort study did not find corresponding associations of potentially explanatory mechanistic variables such as atopic eczema, allergic sensitization, and bronchial hyperresponsiveness, leaving open questions about pathophysiology and roles of irritancy versus allergy. For the Southern California Children's Study non-freewway pollutants demonstrated a stronger effect than those from freeways, possibly reflecting an effect of frequent acceleration and deceleration on TRAP characteristics.

In a smaller study, Carlsten et al (2011) recruited infants at high familial risk for asthma and examined birth year home exposures to NO, NO ₂, black carbon, and PM 2.5 by land use regression with follow up at 7 years of age. Birth year PM 2.5 (IQR=4.1ug/m3) was associated with a significantly increased risk of asthma with an OR of 3.1 (1.3-7.4). NO and NO ₂ demonstrated similar associations but black carbon did not. This dramatic finding with relatively small exposure magnitude is intriguing but needs replication.

A study of self-reported allergic disease (using the ISAAC questionnaire) and home traffic density based on distance to major roadways, found approximately 1.5 to 3 fold prevalence ratios for heavy traffic density for wheeze, asthma, rhinitis and rhinoconjunctivitis, with no associations for children who slept in air conditioned homes, with obvious important implications for prevention in atopics and others at heightened risk.

Using a cross sectional design and an "enhanced" ISAAC protocol for outcomes, 6683 children in the French Six Cities Study were studied, with exposures based on a 3-year dispersion model for each school address to assign individual school exposures,. Asthma (either past year, or lifetime) was significantly associated with benzene, SO ₂, PM ₁₀, NOx, and CO. All of those but SO ₂ were associated with eczema, and allergic rhinitis with PM ₁₀,. Sensitization to pollens was associated with benzene and PM ₁₀, The findings for benzene and CO are somewhat surprising, and given their presence as constituents of motor vehicle fuel and/or exhaust, uncontrolled confounding may be present.

TRAP and Adult Asthma

The recent data base on asthma and traffic is less robust in adults. The Swiss Cohort Study on Air Pollution and Lung Diseases in Adults (SAPALDIA) is a Swiss population-based cohort of adult lung disease-free non-smokers initiated in 1991 with 11y follow in 2002. Using a dispersion model that included hourly meteorological and emission data on industrial, construction, heating, agricultural and forestry, and traffic emissions, the latter separated by type of vehicle (truck vs. car), each participant was assigned an exposure to PM ₁₀. Outcomes were adjusted for age, gender, baseline atopy, BMI, bronchial reactivity, and maternal allergies. They found a hazard ratio for doctor-diagnosed asthma of 1.30 (1.05-1.61) new cases for a given (1ug/m3 as PM ₁₀) change in traffic pollution over the 10 years, more frequent in those with baseline atopy or bronchial hyperreactivity.

Trupin et al looked at the simultaneous impact on FEV1 percent and an asthma severity score of diverse social and physical environmental exposures on adult asthma in 176 subjects. Their final model had an R ² of 0.30 for FEV1 percent predicted and 0.16 for Severity of Asthma Score. Distance to nearest road was a significant predictor of FEV1 but not Severity of Asthma Score. The importance here is that even when other variables strongly associated with usual clinical management of asthma are accounted for, a role for roadway traffic still persists.

Based on high quality studies discussed herein there is an increasingly robust literature that supports a causal relationship between various aspects of TRAP and new onset asthma or worsened asthma in children and adults. These risks need to be both incorporated into both public policy and explored for their role in medical decision making at the individual level.

BMF and asthma

In contrast to the abundance of studies showing exacerbation of asthma from increased exposure to ambient air pollution and TRAP, asthma prevalence has been the main outcome considered in studies of BMF smoke. Using Burden of Obstructive Lung Disease (BOLD) data on self-reported prevalence of asthma among 508 individuals in Southeastern Kentucky, increased odds of reporting current asthma was associated with cooking indoors with wood or coal for more than 6 months of one's life (OR 2.3, CI 1.1-5.0), but not with history of domestic heating with wood or coal (OR 0.8, CI 0.4-1.8). However, a handful of earlier studies had not found compelling evidence of an increased risk of asthma among women or children in households using BMF. Among six studies that examined risk of asthma among women using BMF in rural India, Iran and Turkey, two found a statistically significant increased risk, and two showed increased risks that were not statistically significant. Using national health survey data, Mishra (2003) found that elderly Indian men and women who lived in households using BMF had a higher prevalence of self-reported asthma compared to those who used cleaner fuels (OR=1.59, CI 1.30-1.94). Also in India, Padhi found increased physician-diagnosed asthma and decline in lung function among rural biomass burners. In a recent meta-analysis, Po et al (2011) found that pooled risk estimates did not provide evidence of overall increased risk of asthma in children or women using BMF. Limitations of the available studies include likely exposure misclassification, outcome misclassification, low power, and/or incomplete control for confounding.

Respiratory Infection

The WHO has concluded that exposure to indoor air pollution doubles the risk of pneumonia and other acute lower respiratory infections, and may account for half of the roughly 800,000 annual worldwide deaths in children under 5 years of age attributed to pneumonia. Dherani et al conducted a meta-analysis of 24 studies, and found that exposure to BMF increased the risk of pneumonia by almost 2-fold. In a meta-analysis that included 8 studies, Po et al found a greater than 3 fold increased risk of acute respiratory infection in children. Deaths among children contribute disproportionately to years of life lost in global burden-of-disease calculations. Increased rates of chronic bronchitis and viral infection have been associated with both gaseous and particulate ambient pollutants, although not specifically with TRAP.

Tuberculosis

Greater use of BMFs appears to be correlated with higher rates of TB infection in global geographic regions, but few studies have evaluated associations at the individual level. In a cross-sectional study of a large national sample of Indian households, Mishra 1999 found increased risk of self-reported TB infection with BMF use (OR 2.58, CI 1.98-3.37), but neither active nor passive smoking was measured. In a later well-designed case-control study in India, Shetty et al 2006 found that risk of bacteriologically or radiographically-confirmed TB was not increased after adjustment for smoking, education, income and other possible confounders. Although a recent systematic review concluded that there was not sufficient epidemiological evidence to support an association between BMF and TB infection, and no epidemiological associations between TRAP and TB have been reported, ambient particles and diesel exhaust particles have been shown to impair macrophage function in animal models, suggesting that such associations are biologically plausible.

Mechanistic Insight

As discussed above, oxidative stress is a commonly cited mechanism for the relationship between air pollutants, many of them with oxidant constituents, and asthma worsening or onset. Both particles and gases may produce oxidative stress and may act in concert. Polymorphisms of GSTM1, GSTP1, and TNF-alpha are all reported to have associations/interactions with asthma and air pollution, but data are not consistent enough to allow firm causal conclusions. Further support for oxidative stress as an explanatory mechanism as to how TRAP exerts effects on intracellular regulation of inflammation and the oxidative stress response comes from an experimental study of air pollution aerosols, including fresh diesel exhaust demonstrating approximately a 10% decease in WBC proteasome activity following 2 hr of aerosol exposure.

Diesel exhaust inhalation is frequently used as a model for acute inhalation of TRAP. Acute exposure to diesel exhaust in a real-world street canyon setting has been shown to significantly reduce pulmonary function in asthmatics (up to 6% decline in FEV1) along with an increase in sputum inflammation as measured by myeloperoxidase. However, experimental exposures to diesel exhaust, despite showing increased airway reactivity in asthmatics, have not elicited evidence of airway inflammation in asthmatic subjects, in surprising contrast to elicitation of inflammatory changes in healthy subjects. Diesel exhaust particles have been shown to have adjuvant effects on IgE synthesis in atopics, so that allergen-specific IgE production upregulates by as much as 50-fold with a skew towards a TH2 profile. Diesel exhaust has been shown to acutely produce human bronchial epithelial inflammation characterized by inflammatory cell recruitment, increased expression of vascular endothelial adhesion molecules, cytokines, mitogen-activated protein kinases, and transcription factors. It has been proposed that epithelial damage from diesel exhaust may lead to decreased mucociliary clearance and consequent increased access of allergens to immune cells in the mucosa. Another recent study examined diesel exhaust produced under realistic conditions to simulate actual driving conditions and emissions. Evaluating inflammatory markers 6 hours after a 1 hour exposure, they found increased expression of p-selectin (p=0.036) and vascular cell adhesion molecule-1 (p=0.030) in bronchial mucosal biopsies as well as the novel finding of increased eosinophils in bronchial alveolar lavage (p=0.017), not previously seen under idling engine conditions. The implications for diesel potentiation of allergic respiratory disease are substantial, especially in light of previous experimental work.

To improve understanding of biological pathways underlying respiratory and cardiovascular effects, a number of panel or experimental studies have measured biomarkers of oxidative stress and inflammation following exposure to TRAP. Examining respiratory effects associated with studies in commuters, there were modest effects of two hour commuting exposures on peak flow, eNO, and airway resistance. Particle number (PN) doses were associated with decreased maximum mid-expiratory flow (MMEF) and FEV1 6 hours after exposure. PN and soot were associated with decreased MMEF and FEV1 immediately after exposure, and increased FeNO after car and bus but not bicycle trips. PN was also associated with an increase in airway resistance immediately but not 6 hours following exposure. There were no associations of exposures or doses with symptoms. They interpreted these findings in healthy individuals to show modest effects of a 2-hour in-traffic exposure on peak flow, eNO, and airway resistance. Examining inflammation and coagulation as a consequence of TRAP exposure, an accompanying study in the same subjects found no consistent associations in blood cell counts, CRP, IL-6, IL-8, IL-10, and TNFa, aPTT, fibrinogen, Factor VII, vWF, and CC 16 6 hours after the commute. Thus these data do not indicate that short term changes predict the serious long-term consequences seen with chronic exposure.

Pollution Intervention studies

Beijing Olympics Intervention Studies

Natural (or politically organized) changes in the environment are viewed by researchers as great opportunities to study the effects on human health of greater than usual degrees of independent variable (pollution) change. This has been applied to the effects of sudden or dramatic changes in air pollution. When these changes are anticipated, detailed clinical studies can be designed. One such example was the Beijing Olympics of 2008. (see ) One study that came out of this examined visits for outpatient treatment of asthma at a Beijing Hospital. During the Olympics, the Chinese government endeavored to reduce air pollution by substantial amounts. While somewhat sparse in clinical detail, they reported a reduction from 12.5 visits per day to 7.3 visits per day, a 41.6% reduction during the Olympic Games.

Also based on the Beijing Olympics, Lin et al (2011) measured serial FeNO as a function of ambient black carbon, a marker of diesel exhaust, in 36 fourth grade Beijing children, before, during, and after the 2008 Beijing Olympics. FeNO was significantly lower during the Olympic period, and increased 16.6% (14.1%-19.2%) per interquartile range increase in BC, particularly in the first hours after exposure, suggesting rapid changes in inflammation. Asthmatics were not significantly different from healthy children.

Intervention Studies for BMF

Romieu (2009) randomized an improved stove (Patsari stove) among 668 households in central Mexico where open wood-burning fires were used for cooking. The stoves had been shown in previous studies to reduce indoor air pollution levels by 70%. At one-year follow-up, among the 50% of households still using the stove, there was a significant reduction in respiratory symptoms and a significantly lower decline in FEV1. Using a randomized controlled trial, Smith et al found that an improved cooking stove halved average exposure to carbon monoxide, but did not significantly reduce physician-diagnosed pneumonia among infants in Guatemala. However, there was a significant reduction in severe pneumonia, and a 50% reduction in exposure was significantly associated with a lower rate of diagnosis of pneumonia. Other randomized controlled trials of improved stoves are underway, but results are yet to be published (Bruce 2007).

Clinical Guidance

Reducing the impact of BMF smoke and TRAP on respiratory health will require both public policy and the actions of individual patients. Consensus standards recognize the importance of air pollutants in the prevention and management of asthma and COPD, and have recommended that clinicians counsel patients to become aware of, and avoid, exposures to air pollution (GOLD and NHLBI Expert Panel 3 report on asthma). Interventions at the individual level may include recommendations by clinicians that patients avoid exercising or cycling near busy roadways to reduce exposure toTRAP, and to improve ventilation in homes were BMF are used. Public policy can encourage or mandate engineering solutions that drastically reduce emissions from cook stoves and vehicles, but adoption of new technologies can be slowed by lack of awareness of health risks, traditional cultural practices, and economic costs. In some respects public health and regulatory approaches to traffic emissions may be considered the low hanging fruit for opportunities toward health improvement on a societal scale. "Experiments" such as the Beijing Olympics have demonstrated how such changes may have health implications.

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Acknowledgements

This work was supported in part from NIEHS P30 ES05022 and USEPA "STAR Grant RD 83457901. Photo credit to Jicheng Gong, M.S., UMDNJ Graduate School of Biomedical Sciences.

Abbreviations

Footnotes

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References

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Respiratory Health Effects of Air Pollution: Update on Biomass Smoke and Traffic Pollution

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Mounting evidence suggests that air pollution contributes to the large global burden of respiratory and allergic diseases including asthma, chronic obstructive pulmonary disease, pneumonia and possibly tuberculosis.

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5. Pollution is not solely a New Delhi or an India problem, it's a global issue.
Pollution in all forms, including air, continue to harm people's health and the environment.

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Despite dramatic progress cleaning the air since 1970, air pollution in the United States continues to harm people's health and the environment. Under the Clean Air Act, EPA continues to work with state, local and tribal governments, other federal agencies, and stakeholders to reduce air pollution and the damage that it causes.

Outdoor air pollution challenges facing the United States today include:
Indoor air pollution, which arises from a variety of causes, also can cause health problems. For more information on indoor air pollution, which is not regulated under the Clean Air Act, see EPA's indoor air web site.

Air Pollution Challenges: Common Pollutants

Great progress has been made in achieving national air quality standards, which EPA originally established in 1971 and updates periodically based on the latest science. One sign of this progress is that visible air pollution is less frequent and widespread than it was in the 1970s.

However, air pollution can be harmful even when it is not visible. Newer scientific studies have shown that some pollutants can harm public health and welfare even at very low levels. EPA in recent years revised standards for five of the six common pollutants subject to national air quality standards. EPA made the standards more protective because new, peer-reviewed scientific studies showed that existing standards were not adequate to protect public health and the environment.

Status of common pollutant problems in brief

Today, pollution levels in many areas of the United States exceed national air quality standards for at least one of the six common pollutants:

Although levels of particle pollution and ground-level ozone pollution are substantially lower than in the past, levels are unhealthy in numerous areas of the country. Both pollutants are the result of emissions from diverse sources, and travel long distances and across state lines.

An extensive body of scientific evidence shows that long- and short-term exposures to fine particle pollution, also known as fine particulate matter (PM2.5), can cause premature death and harmful effects on the cardiovascular system, including increased hospital admissions and emergency department visits for heart attacks and strokes. Scientific evidence also links PM to harmful respiratory effects, including asthma attacks.

Ozone can increase the frequency of asthma attacks, cause shortness of breath, aggravate lung diseases, and cause permanent damage to lungs through long-term exposure. Elevated ozone levels are linked to increases in hospitalizations, emergency room visits and premature death.

Both pollutants cause environmental damage, and fine particles impair visibility.

Fine particles can be emitted directly or formed from gaseous emissions including sulfur dioxide or nitrogen oxides. Ozone, a colorless gas, is created when emissions of nitrogen oxides and volatile organic compounds react.

For unhealthy peak levels of sulfur dioxide and nitrogen dioxide, EPA is working with states and others on ways to determine where and how often unhealthy peaks occur. Both pollutants cause multiple adverse respiratory effects including increased asthma symptoms, and are associated with increased emergency department visits and hospital admissions for respiratory illness. Both pollutants cause environmental damage, and are byproducts of fossil fuel combustion.

Airborne lead pollution, a nationwide health concern before EPA phased out lead in motor vehicle gasoline under Clean Air Act authority, now meets national air quality standards except in areas near certain large lead-emitting industrial facilities. Lead is associated with neurological effects in children, such as behavioral problems, learning deficits and lowered IQ, and high blood pressure and heart disease in adults.

The entire nation meets the carbon monoxide air quality standards, largely because of emissions standards for new motor vehicles under the Clean Air Act.

In Brief: How EPA is working with states and tribes to limit common air pollutants

EPA's air research provides the critical science to develop and implement outdoor air regulations under the Clean Air Act and puts new tools and information in the hands of air quality managers and regulators to protect the air we breathe.

To reflect new scientific studies, EPA revised the national air quality standards for fine particles (2006, 2012), ground-level ozone (2008, 2015), sulfur dioxide (2010), nitrogen dioxide (2010), and lead (2008). After the scientific review, EPA decided to retain the existing standards for carbon monoxide. EPA strengthened the air quality standards for ground-level ozone in October 2015 based on extensive scientific evidence about ozone's effects.

EPA has designated areas meeting and not meeting the air quality standards for the 2006 and 2012 PM standards and the 2008 ozone standard, and has completed an initial round of area designations for the 2010 sulfur dioxide standard. The agency also issues rules or guidance for state implementation of the various ambient air quality standards - for example, in March 2015, proposing requirements for implementation of current and future fine particle standards. EPA is working with states to improve data to support implementation of the 2010 sulfur dioxide and nitrogen dioxide standards.

For areas not meeting the national air quality standards, states are required to adopt state implementation plan revisions containing measures needed to meet the standards as expeditiously as practicable and within time periods specified in the Clean Air Act (except that plans are not required for areas with "marginal" ozone levels).

EPA is helping states to meet standards for common pollutants by issuing federal emissions standards for new motor vehicles and non-road engines, national emissions standards for categories of new industrial equipment (e.g., power plants, industrial boilers, cement manufacturing, secondary lead smelting), and technical and policy guidance for state implementation plans. EPA and state rules already on the books are projected to help 99 percent of counties with monitors meet the revised fine particle standards by 2020. The Mercury and Air Toxics Standards for new and existing power plants issued in December 2011 are achieving reductions in fine particles and sulfur dioxide as a byproduct of controls required to cut toxic emissions.

Vehicles and their fuels continue to be an important contributor to air pollution. EPA in 2014 issued standards commonly known as Tier 3, which consider the vehicle and its fuel as an integrated system, setting new vehicle emissions standards and a new gasoline sulfur standard beginning in 2017. The vehicle emissions standards will reduce both tailpipe and evaporative emissions from passenger cars, light-duty trucks, medium-duty passenger vehicles, and some heavy-duty vehicles. The gasoline sulfur standard will enable more stringent vehicle emissions standards and will make emissions control systems more effective. These rules further cut the sulfur content of gasoline. Cleaner fuel makes possible the use of new vehicle emission control technologies and cuts harmful emissions in existing vehicles. The standards will reduce atmospheric levels of ozone, fine particles, nitrogen dioxide, and toxic pollution.

Learn more about common pollutants, health effects, standards and implementation:

Air Pollution Challenges: Climate Change

EPA determined in 2009 that emissions of carbon dioxide and other long-lived greenhouse gases that build up in the atmosphere endanger the health and welfare of current and future generations by causing climate change and ocean acidification. Long-lived greenhouse gases, which trap heat in the atmosphere, include carbon dioxide, methane, nitrous oxide, and fluorinated gases. These gases are produced by a numerous and diverse human activities.

In May 2010, the National Research Council, the operating arm of the National Academy of Sciences, published an assessment which concluded that "climate change is occurring, is caused largely by human activities, and poses significant risks for - and in many cases is already affecting - a broad range of human and natural systems." The NRC stated that this conclusion is based on findings that are consistent with several other major assessments of the state of scientific knowledge on climate change.

Climate change impacts on public health and welfare

The risks to public health and the environment from climate change are substantial and far-reaching. Scientists warn that carbon pollution and resulting climate change are expected to lead to more intense hurricanes and storms, heavier and more frequent flooding, increased drought, and more severe wildfires - events that can cause deaths, injuries, and billions of dollars of damage to property and the nation's infrastructure.

Carbon dioxide and other greenhouse gas pollution leads to more frequent and intense heat waves that increase mortality, especially among the poor and elderly. Other climate change public health concerns raised in the scientific literature include anticipated increases in ground-level ozone pollution, the potential for enhanced spread of some waterborne and pest-related diseases, and evidence for increased production or dispersion of airborne allergens.

Other effects of greenhouse gas pollution noted in the scientific literature include ocean acidification, sea level rise and increased storm surge, harm to agriculture and forests, species extinctions and ecosystem damage. Climate change impacts in certain regions of the world (potentially leading, for example, to food scarcity, conflicts or mass migration) may exacerbate problems that raise humanitarian, trade and national security issues for the United States.

The U.S. government's May 2014 National Climate Assessment concluded that climate change impacts are already manifesting themselves and imposing losses and costs. The report documents increases in extreme weather and climate events in recent decades, with resulting damage and disruption to human well-being, infrastructure, ecosystems, and agriculture, and projects continued increases in impacts across a wide range of communities, sectors, and ecosystems.

Those most vulnerable to climate related health effects - such as children, the elderly, the poor, and future generations - face disproportionate risks. Recent studies also find that certain communities, including low-income communities and some communities of color (more specifically, populations defined jointly by ethnic/racial characteristics and geographic location), are disproportionately affected by certain climate-change-related impacts - including heat waves, degraded air quality, and extreme weather events - which are associated with increased deaths, illnesses, and economic challenges. Studies also find that climate change poses particular threats to the health, well-being, and ways of life of indigenous peoples in the U.S.

The National Research Council (NRC) and other scientific bodies have emphasized that it is important to take initial steps to reduce greenhouse gases without delay because, once emitted, greenhouse gases persist in the atmosphere for long time periods. As the NRC explained in a recent report, "The sooner that serious efforts to reduce greenhouse gas emissions proceed, the lower the risks posed by climate change, and the less pressure there will be to make larger, more rapid, and potentially more expensive reductions later."

In brief: What EPA is doing about climate change

Under the Clean Air Act, EPA is taking initial common sense steps to limit greenhouse gas pollution from large sources:

EPA and the National Highway and Traffic Safety Administration between 2010 and 2012 issued the first national greenhouse gas emission standards and fuel economy standards for cars and light trucks for model years 2012-2025, and for medium- and heavy-duty trucks for 2014-2018. Proposed truck standards for 2018 and beyond were announced in June 2015. EPA is also responsible for developing and implementing regulations to ensure that transportation fuel sold in the United States contains a minimum volume of renewable fuel. Learn more about clean vehicles

EPA and states in 2011 began requiring preconstruction permits that limit greenhouse gas emissions from large new stationary sources - such as power plants, refineries, cement plants, and steel mills - when they are built or undergo major modification. Learn more about GHG permitting

On August 3, 2015, President Obama and EPA announced the Clean Power Plan - a historic and important step in reducing carbon pollution from power plants that takes real action on climate change. Shaped by years of unprecedented outreach and public engagement, the final Clean Power Plan is fair, flexible and designed to strengthen the fast-growing trend toward cleaner and lower-polluting American energy. With strong but achievable standards for power plants, and customized goals for states to cut the carbon pollution that is driving climate change, the Clean Power Plan provides national consistency, accountability and a level playing field while reflecting each state's energy mix. It also shows the world that the United States is committed to leading global efforts to address climate change. Learn more about the Clean Power Plan, the Carbon Pollution Standards, the Federal Plan, and model rule for states

The Clean Power Plan will reduce carbon pollution from existing power plants, the nation's largest source, while maintaining energy reliability and affordability. The Clean Air Act creates a partnership between EPA, states, tribes and U.S. territories - with EPA setting a goal, and states and tribes choosing how they will meet it. This partnership is laid out in the Clean Power Plan.

Also on August 3, 2015, EPA issued final Carbon Pollution Standards for new, modified, and constructed power plants, and proposed a Federal Plan and model rules to assist states in implementing the Clean Power Plan.

On February 9, 2016, the Supreme Court stayed implementation of the Clean Power Plan pending judicial review. The Court's decision was not on the merits of the rule. EPA firmly believes the Clean Power Plan will be upheld when the merits are considered because the rule rests on strong scientific and legal foundations.

On October 16, 2017, EPA proposed to repeal the CPP and rescind the accompanying legal memorandum.

EPA is implementing its Strategy to Reduce Methane Emissions released in March 2014. In January 2015 EPA announced a new goal to cut methane emissions from the oil and gas sector by 40 - 45 percent from 2012 levels by 2025, and a set of actions by EPA and other agencies to put the U.S. on a path to achieve this ambitious goal. In August 2015, EPA proposed new common-sense measures to cut methane emissions, reduce smog-forming air pollution and provide certainty for industry through proposed rules for the oil and gas industry. The agency also proposed to further reduce emissions of methane-rich gas from municipal solid waste landfills. In March 2016 EPA launched the National Gas STAR Methane Challenge Program under which oil and gas companies can make, track and showcase ambitious commitments to reduce methane emissions.

EPA in July 2015 finalized a rule to prohibit certain uses of hydrofluorocarbons -- a class of potent greenhouse gases used in air conditioning, refrigeration and other equipment -- in favor of safer alternatives. The U.S. also has proposed amendments to the Montreal Protocol to achieve reductions in HFCs internationally.

Learn more about climate science, control efforts, and adaptation on EPA's climate change web site
Air Pollution Challenges: Toxic Pollutants

While overall emissions of air toxics have declined significantly since 1990, substantial quantities of toxic pollutants continue to be released into the air. Elevated risks can occur in urban areas, near industrial facilities, and in areas with high transportation emissions.

Numerous toxic pollutants from diverse sources

Hazardous air pollutants, also called air toxics, include 187 pollutants listed in the Clean Air Act. EPA can add pollutants that are known or suspected to cause cancer or other serious health effects, such as reproductive effects or birth defects, or to cause adverse environmental effects.

Examples of air toxics include benzene, which is found in gasoline; perchloroethylene, which is emitted from some dry cleaning facilities; and methylene chloride, which is used as a solvent and paint stripper by a number of industries. Other examples of air toxics include dioxin, asbestos, and metals such as cadmium, mercury, chromium, and lead compounds.

Most air toxics originate from manmade sources, including mobile sources such as motor vehicles, industrial facilities and small "area" sources. Numerous categories of stationary sources emit air toxics, including power plants, chemical manufacturing, aerospace manufacturing and steel mills. Some air toxics are released in large amounts from natural sources such as forest fires.

Health risks from air toxics

EPA's most recent national assessment of inhalation risks from air toxics estimated that the whole nation experiences lifetime cancer risks above ten in a million, and that almost 14 million people in more than 60 urban locations have lifetime cancer risks greater than 100 in a million. Since that 2005 assessment, EPA standards have required significant further reductions in toxic emissions.

Elevated risks are often found in the largest urban areas where there are multiple emission sources, communities near industrial facilities, and/or areas near large roadways or transportation facilities. Benzene and formaldehyde are two of the biggest cancer risk drivers, and acrolein tends to dominate non-cancer risks.

In brief: How EPA is working with states and communities to reduce toxic air pollution

EPA standards based on technology performance have been successful in achieving large reductions in national emissions of air toxics. As directed by Congress, EPA has completed emissions standards for all 174 major source categories, and 68 categories of small area sources representing 90 percent of emissions of 30 priority pollutants for urban areas. In addition, EPA has reduced the benzene content in gasoline, and has established stringent emission standards for on-road and nonroad diesel and gasoline engine emissions that significantly reduce emissions of mobile source air toxics. As required by the Act, EPA has completed residual risk assessments and technology reviews covering numerous regulated source categories to assess whether more protective air toxics standards are warranted. EPA has updated standards as appropriate. Additional residual risk assessments and technology reviews are currently underway.

EPA also encourages and supports area-wide air toxics strategies of state, tribal and local agencies through national, regional and community-based initiatives. Among these initiatives are the National Clean Diesel Campaign, which through partnerships and grants reduces diesel emissions for existing engines that EPA does not regulate; Clean School Bus USA, a national partnership to minimize pollution from school buses; the SmartWay Transport Partnership to promote efficient goods movement; wood smoke reduction initiatives; a collision repair campaign involving autobody shops; community-scale air toxics ambient monitoring grants; and other programs including Community Action for a Renewed Environment (CARE). The CARE program helps communities develop broad-based local partnerships (that include business and local government) and conduct community-driven problem solving as they build capacity to understand and take effective actions on addressing environmental problems.
Learn more about air toxics, stationary sources of emissions, and control efforts
Learn more about mobile source air toxics and control efforts
Air Pollution Challenges: Protecting the Stratospheric Ozone Layer

The ozone (O₃) layer in the stratosphere protects life on earth by filtering out harmful ultraviolet radiation (UV) from the sun. When chlorofluorocarbons (CFCs) and other ozone-degrading chemicals are emitted, they mix with the atmosphere and eventually rise to the stratosphere. There, the chlorine and the bromine they contain initiate chemical reactions that destroy ozone. This destruction has occurred at a more rapid rate than ozone can be created through natural processes, depleting the ozone layer.

The toll on public health and the environment

Higher levels of ultraviolet radiation reaching Earth's surface lead to health and environmental effects such as a greater incidence of skin cancer, cataracts, and impaired immune systems. Higher levels of ultraviolet radiation also reduce crop yields, diminish the productivity of the oceans, and possibly contribute to the decline of amphibious populations that is occurring around the world.

In brief: What's being done to protect the ozone layer

Ensure that refrigerants and halon fire extinguishing agents are recycled properly.

Ensure that alternatives to ozone-depleting substances (ODS) are evaluated for their impacts on human health and the environment.

Ban the release of ozone-depleting refrigerants during the service, maintenance, and disposal of air conditioners and other refrigeration equipment.

Require that manufacturers label products either containing or made with the most harmful ODS.

Countries around the world are phasing out the production of chemicals that destroy ozone in the Earth's upper atmosphere under an international treaty known as the Montreal Protocol. Using a flexible and innovative regulatory approach, the United States already has phased out production of those substances having the greatest potential to deplete the ozone layer under Clean Air Act provisions enacted to implement the Montreal Protocol. These chemicals include CFCs, halons, methyl chloroform and carbon tetrachloride. The United States and other countries are currently phasing out production of hydrochlorofluorocarbons (HCFCs), chemicals being used globally in refrigeration and air-conditioning equipment and in making foams. Phasing out CFCs and HCFCs is also beneficial in protecting the earth's climate, as these substances are also very damaging greenhouse gases.

Also under the Clean Air Act, EPA implements regulatory programs to:

Continuing to provide forecasts of the expected risk of overexposure to UV radiation from the sun through the UV Index, and to educate the public on how to protect themselves from over exposure to UV radiation.

Continuing to foster domestic and international partnerships to protect the ozone layer.

Encouraging the development of products, technologies, and initiatives that reap co-benefits in climate change and energy efficiency.

Learn more About EPA's Ozone Layer Protection Programs
These vital measures are helping to protect human health and the global environment.

The work of protecting the ozone layer is not finished. EPA plans to complete the phase-out of ozone-depleting substances that continue to be produced, and continue efforts to minimize releases of chemicals in use. Since ozone-depleting substances persist in the air for long periods of time, the past use of these substances continues to affect the ozone layer today. In our work to expedite the recovery of the ozone layer, EPA plans to augment CAA implementation by:

References

1 National Research Council (2010), Advancing the Science of Climate Change, National Academy Press, Washington, D.C., p. 3.

2 National Research Council (2010), Advancing the Science of Climate Change, National Academy Press, Washington, D.C., p. 286.

3 USGCRP (2009). Global Climate Change Impacts in the United States. Karl, T.R., J.M. Melillo, and T.C. Peterson (eds.). United States Global Change Research Program. Cambridge University Press, New York, NY, USA.

4 CCSP (2008). Analyses of the effects of global change on human health and welfare and human systems. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. Gamble, J.L. (ed.), K.L. Ebi, F.G. Sussman, T.J. Wilbanks, (Authors). U.S. Environmental Protection Agency, Washington, DC, USA.

5 Confalonieri, U., B. Menne, R. Akhtar, K.L. Ebi, M. Hauengue, R.S. Kovats, B. Revich and A. Woodward (2007). Human health. In: Climate Change 2007: Impacts, Adaptation and Vulnerability . Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change Parry, M.L., O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, (eds.), Cambridge University Press, Cambridge, United Kingdom.

6 Ibid.

7 An explanation of observed and projected climate change and its associated impacts on health, society, and the environment is included in the EPA's Endangerment Finding and associated technical support document (TSD). See EPA, " Endangerment and Cause or Contribute Findings for Greenhouse Gases under Section 202(a) of the Clean Air Act," 74 FR 66496, Dec. 15, 2009. Both the Federal Register Notice and the Technical Support Document (TSD) for Endangerment and Cause or Contribute Findings are found in the public docket, Docket No. EPA-OAR-2009-0171.

8 EPA, Endangerment Finding, 74 FR 66535.

9 U.S. Global Change Research Program, Climate Change Impacts in the United States: The Third National Climate Assessment, May 2014.

10 EPA, Endangerment Finding, 74 FR 66498.

11 National Research Council (2011) America's Climate Choices: Report in Brief, Committee on America's Climate Choices, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, The National Academies Press, Washington, D.C., p. 2.

12 EPA, 2005 National-Scale Air Toxics Assessment (2011).

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Air Pollution: Current and Future Challenges | US EPA

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Despite the dramatic progress to date, air pollution continues to threaten Americans' health and welfare. The main obstacles are climate change, conventional air pollution, and ozone layer depletion.

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2. According to GreenPeace and AirVisual, New Delhi has an average air quality index of 135.8 in 2018...almost three times the levels which the US Environmental Protection agency regards as healthy.

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most polluted cities in the world: 22 of the top 30 are in india - cnn

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22 of the top 30 most polluted cities in the world are in India

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India accounts for seven of the world's 10 cities with the worst air pollution, according to a new report, but previously smogbound Chinese cities have seen a marked improvement.

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"Extreme pollution has become its own season"
- Burning Bans
- Waste Management
- Planting Trees
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Over the past few months, a series of air pollution episodes have set new records across Asia. Earlier this summer, hundreds of people were evacuated, and schools had to be closed due to poor air quality in many parts of Indonesia, during a crisis that made the skies over the region turn red. More recently, air quality levels have worsened in India creating public outcry with dire consequences for large swaths of society. The spikes, especially in fine particulate matter (PM2.5), have caused closure of schools, declaration of health emergency by the state government, demonstrations by civil society and alarming media coverage.

These recurrent episodes now happen every year like clockwork during the beginning of winter, aggravated by the festive season. In India, extreme air pollution has become its own season, from October to February. A major cause is intentional burning to clear agricultural residue and forests in the neighbouring states of Haryana, Punjab, UP and Rajasthan, as well as household fires for cooking and heating. These practices worsen the already bad air quality levels caused by pollution from transport, energy and industrial sources.

Extreme air pollution episodes affect millions of people in densely populated regions who are exposed to thick, toxic smog for weeks. Local public health experts estimate that by the time kids come back from school they have been exposed to air pollution level equivalent to smoking 50 to 60 cigarettes in the national capital region. Similarly, vulnerable sectors of society are disproportionally exposed to this environmental threat.

Particulate matter found in the smog and air pollution has negative effects on human health and, according to the World Health Organization, is responsible for 7 million premature deaths worldwide each year. In the countries affected by such dramatic episodes, as well as by overall high levels of air pollution, this environmental threat represents the second or third most serious risk factor for public health.

A recent report by the Health Effects Institute highlighted that, if no additional measures are taken to change the ongoing regular air pollution crises, deaths from air pollution in India will rise from 1.1 million in 2015 to 1.7 million deaths annually in 2030 and 3.6 million deaths annually by 2050.

Such mortality and morbidity impacts translate into significant economic losses (approximately up to 1 per cent of India's gross domestic product) as has been estimated thanks to the ongoing work on the impact of air pollution on India's human capital and economy, by the UN Environment Programme (UNEP) and University of Delhi.

"Besides air pollution's detrimental impact on our health, this out of proportion environmental threat also impacts our economies, our food security, our climate, and it exacerbates inequalities," said Soraya Smaoun, UNEP's Air Quality Coordinator. Air pollution and climate change are intrinsically linked, since air pollutants impact the climate and are often co-emitted with greenhouse gases.

With Asia having experienced the most dramatic episodes of air pollution in recent years, many studies have focused on regional solutions. In 2016, the Climate and Clean Air Coalition commissioned a report to find solutions to air pollution in Indian cities. The report Breathing Cleaner Air: Ten Scalable Solutions for Indian Cities was led by a task force of Indian and international experts. It outlined solutions that can significantly reduce air pollution in the country, including preventing agricultural open burning by turning crop residue into a resource to produce fuel for electricity generation.

A similar report focusing on regional solutions was published by UNEP and the Climate and Clean Air Coalition last year called Air Pollution in Asia and the Pacific: Science-based Solutions, detailing 25 policy and technological measures that will deliver benefits across sectors. It represented the first comprehensive scientific assessment of the air pollution outlook in Asia and the Pacific and highlighted that adopting the 25 recommended measures could lead to a reduction in premature mortality in the region by one third, helping to avoid 2 million premature deaths from indoor air pollution per year.

Reports converge on the finding that local governments must play a central role in the fight to #BeatAirPollution in the region. Jambi City, which received international media attention due to its sky turning red during the latest crisis in Indonesia, has approved an emissions mitigation plan that includes reducing and capturing methane from waste, local regulations that ban waste burning and planting trees to make its neighbourhoods greener. Having recently joined the BreatheLife network, it is but one example of how cities are taking the lead in Asia to improve air quality and protect their citizens and our planet.

Furthermore, this year the Indian government joined the Climate and Clean Air Coalition on the occasion of World Environment Day. India's Minister for Environment, Forest and Climate Change, Prakash Javadekar, stated then that India will work to "adopt cleaner energy, sustainable production and consumption patterns" as well as "environment-friendly transport, agriculture, industry and waste management to promote clean air".

The UN Environment Assembly, together with other global entities, has called for heightened action to improve air quality and to address pollution in general. Global political momentum is supported by regional political processes that recognize health and the environment as a priority in Asia and the Pacific. These are a good foundation for taking more decisive action.

The current extreme air pollution episodes in Asia are part of a serious, persistent, global air pollution problem, which involves the transport and agricultural sectors, household energy, industry as well as waste management practices. It is therefore imperative that coordinated efforts led by local and national governments and supported by existing tools and international experience take place in order to protect ourselves, our economies and our planet from the detrimental effects of this growing environmental threat.
The BreatheLife network, a joint effort by the World Health Organization, the UN Environment Programme and the Climate and Clean Air Coalition, is working with local and national governments to design and implement policies that improve air quality levels in urban areas. It also mobilizes and empowers citizens to take personal responsibility to prevent air pollution and protect our health and planet from its effects. Cities use BreatheLife as a platform to share best practices and demonstrate progress in their journey to meeting World Health Organization air quality targets by 2030, and to build demand for new solutions and ways to take action both locally and globally.

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A new wave of air pollution crises: what can be done?

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Over the past few months, a series of air pollution episodes have set new records across Asia. Earlier this summer, hundreds of people were evacuated, and schools had to be closed due to poor air quality in many parts of Indonesia, during a crisis that made the skies over the region turn red.

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-Conservation
- Carpooling
- Maintenance
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Actions You Can Take to Reduce Air Pollution

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An official website of the United States government