Levels of development vary. 

> The towns near Metro Manila have become industrialized whereas the inner towns continue to engage in agricultural production or pursue agri-based industries and cottage and small-scale industries

Key sources of nutrients include run-off from farmland treated with fertilizers as well as detergents and untreated sewage in domestic wastewater.

According to UN Environment’s Christopher Cox, it is one of the key environmental issues facing the planet today.
“Building awareness of the nutrient challenge is crucial,” Cox says. 

“Nutrient loads into coastal areas rose as much as 80 per cent between 1970 and 2000, but more than 80 per cent of wastewater is still released into the environment without treatment. If we don’t address this issue, the results – from ocean hypoxia to toxic algal blooms – could be catastrophic.”