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A comprehensive survey of the drinking water for more than 28 million Americans has detected the widespread but low-level presence of pharmaceuticals and hormonally active chemicals.

Little was known about people's exposure to such compounds from drinking water, so Shane Snyder and colleagues at the Southern Nevada Water Authority in Las Vegas screened tap water from 19 US water utilities for 51 different compounds. The surveys were carried out between 2006 and 2007.

The 11 most frequently detected compounds - all found at extremely low concentrations - were&colon;

* Atenolol, a beta-blocker used to treat cardiovascular disease

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* Atrazine, an organic herbicide banned in the European Union, but still used in the US, which has been implicated in the decline of fish stocks and in changes in animal behaviour

* Carbamazepine, a mood-stabilising drug used to treat bipolar disorder, amongst other things

* Estrone, an oestrogen hormone secreted by the ovaries and blamed for causing gender-bending changes in fish

* Gemfibrozil, an anti-cholesterol drug

* Meprobamate, a tranquiliser widely used in psychiatric treatment

* Naproxen, a painkiller and anti-inflammatory linked to increases in asthma incidence

* Phenytoin, an anticonvulsant that has been used to treat epilepsy

* Sulfamethoxazole, an antibiotic used against the Streptococcus bacteria, which is responsible for tonsillitis and other diseases

* TCEP, a reducing agent used in molecular biology

* Trimethoprim, another antibiotic

The concentrations of pharmaceuticals in drinking water were millions of times lower than in a medical dose, and Snyder emphasises that they pose no public health threat. He cautions, though, that "if a person has a unique health condition, or is concerned about particular contaminants in public water systems, I strongly recommend they consult their physician".

Christian Daughton of the EPA's National Exposure Research Laboratory says that neither this nor other recent water assessments give cause for health concern. "But several point to the potential for risk - especially for the fetus and those with severely compromised health."

Daughton says the contamination surveys help people realise how they are intimately and inseparably connected with their environment. "The occurrence of pharmaceuticals in the environment also serves to make us acutely aware of the chemical sea that surrounds us," he says.

Modern life

While the US government regulates the levels of pathogens in US drinking water, there are no rules for pharmaceuticals and other compounds, apart from one&colon; the herbicide atrazine. The atrazine levels measured by Snyder and colleagues were well within federal limits.

Snyder says water utilities could make drinking water purer. But the costs of "extreme purification" - far beyond what is needed for safety alone - are huge in terms of increased energy usage and carbon footprint. Ultra-pure water might not even be safe, adds Snyder.

The widespread occurrence of pharmaceuticals and endocrine disruptors reflects improved detection techniques, rather than greater pollution, says Snyder. Contamination is a fact of modern life, he adds.

"As we continue to populate and aggregate, our wastes will certainly accumulate where we live," he says. "We as a species have decided to live a modern life, with pharmaceuticals, plastics, transportation - therefore we must accept that there will be a certain degree of contamination."

Journal reference&colon; Environmental Science and Technology, in press

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A comprehensive survey of the drinking water for more than 28 million Americans has detected the widespread but low-level presence of pharmaceuticals and hormonally active chemicals. Little was known about people's exposure to such compounds from drinking water, so Shane Snyder and colleagues at the Southern Nevada Water Authority in Las Vegas screened tap water from 19 US water utilities for 51 different compounds.

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9. Copy this list of Molecules. Circle the molecules that are also compounds.

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9. Copy this list of Molecules. Circle the molecules that are also compounds.

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N2
H2
H₂O
03
NO3
C₆H₁₂O6

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Use the supplies at the table to create a model of an Atom, Element, and Compound Your Model should be used the explain the difference between Atoms, Elements and Molecules.

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8. What is a Molecule? What is a Compound?

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8. What is a Molecule? What is a Compound?

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Define Molecule and Compound in your notes

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what is the difference between a compound and a molecule

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Questions and Answers - What is the difference between a compound and a molecule?

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An answer to the question: What is the difference between a compound and a molecule?

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The periodic table of elements is a chart that names the elements and their characteristics.  Get a periodic table of elements from Ms Montoya and find the names for these elements:

1. Na
2. Cl
3. H
4. O
5. C
6. Ag
7. Au

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7. COPY THIS IN YOUR NOTEBOOK:  "Instead of writing the entire name of an element, an abbreviation for each element is used. Each element is given a CAPITOL letter (and maybe a lower case letter) to identify it."

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7. COPY THIS IN YOUR NOTEBOOK:  "Instead of writing the entire name of an element, an abbreviation for each element is used. Each element is given a CAPITOL letter (and maybe a lower case letter) to identify it."

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STOP HERE AND WAIT FOR CLASS CHECK FOR UNDERSTANDING.

If you need to wait, get a periodic table scavenger hunt from Ms. Montoya. Use the interactive periodic table for information.

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Interactive Periodic Table of the Elements, in Pictures and Words

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Interactive Periodic Table of the Elements, in Pictures and Words

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A. What is an element?
B. What is the difference between the element oxygen and the element nitrogen?

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Chem4Kids.com: Elements & Periodic Table

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Chem4Kids.com! This tutorial introduces basics of elements and their organization. Other sections include matter, elements, reactions, and biochemistry.

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4. Based on what you know about gravity - why do you think the electrons in the outermost layer of an atom are the ones that react with other atoms?

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4. Based on what you know about gravity - why do you think the electrons in the outermost layer of an atom are the ones that react with other atoms?

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3. What is a valence electron? Research on your own and add that term to your drawing.

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3. What is a valence electron? Research on your own and add that term to your drawing.

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2. Look at this image of the Bohr model of an atom. Draw and label the electrons, protons, neutrons and nucleus in this model.

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2. Look at this image of the Bohr model of an atom. Draw and label the electrons, protons, neutrons and nucleus in this model.

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Go to the website to answer this question in your notes (define these key terms: protons, neutrons, electrons, )

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Atoms are the foundation of chemistry. They are the basis for everything in the Universe. As you know, matter is composed of atoms. Solids are made of densely packed atoms while gases have atoms that are spread out. We're going to cover basics like atomic structure and bonding between atoms. As you learn more, you can move to the reactions and biochemistry pages and see how atoms form compounds that help the biological world survive.

Are there pieces of matter that are smaller than atoms? Sure there are. Super-small particles can be found inside the pieces of atoms. These subatomic particles include nucleons and quarks. Nuclear chemists and physicists work together at particle accelerators to discover the presence of these tiny, tiny, tiny pieces of matter. However, science is based on the atom because it is the smallest distinct unit of matter.

Even though many super-tiny atomic particles exist, you only need to remember the three basic parts of an atom: electrons, protons, and neutrons. What are electrons, protons, and neutrons? Electrons are the smallest of the three particles that make up atoms. Electrons are found in shells or orbitals that surround the nucleus of an atom. Protons and neutrons are found in the nucleus. They group together in the center of the atom. That's all you have to remember. Three easy pieces!

There are almost 120 known elements in the periodic table. (117 as we write this) Chemists and physicists are trying to make new ones every day in their labs. The atoms of different elements have different numbers of electrons, protons, and neutrons. Every element is unique and has an atomic number. That number tells you the number of protons in every atom of the element. The atomic number is also called the proton number.

You can see that each part of the atom is labeled with a "+", "-", or a "0." Those symbols refer to the charge of the particle. Have you ever heard about getting a shock from a socket, static electricity, or lightning? Those are all related to electric charges. Charges are also found in tiny particles of matter.

The electron always has a "-", or negative, charge. The proton always has a "+", or positive, charge. If the charge of an entire atom is "0", or neutral, there are equal numbers of positive and negative charges. Neutral atoms have equal numbers of electrons and protons. The third particle is the neutron. It has a neutral charge, also known as a charge of zero.

Since the number of protons in an atom does not change, fewer or extra electrons can create a special atom called an ion. Cations have fewer electrons and have a positive charge. Anions have extra electrons that create a negative charge.

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Chem4Kids.com! This tutorial introduces atomic structure in chemistry. Other sections include matter, elements, the periodic table, reactions, and biochemistry.