It also ranked second-worst, behind Los Angeles, for smog levels, known formally as ozone pollution.
The ALA analyzed the data based on ozone pollution, short-term particle pollution and year-round particle pollution.
Ozone pollution has adverse effects on health as well, but is not as dangerous in the short-term.
Most cities that topped the ALA's most polluted lists for particle and ozone pollution have seen their levels decrease.
The seven worst metropolitan areas for ozone pollution are all in California.
The ALA assessed levels of ozone pollution, more commonly known as smog, and levels of particle pollution, or air-born toxins that can potentially be lethal if inhaled at high enough levels.
Four in 10 Americans live in counties with dangerous levels of either ozone or particle pollution, according to the American Lung Association.
The main reason behind the depletion of the Ozone layer is industrial pollution which is produced by some of the world most industrialized states.
What ails Modesto is what ails Bakersfield (No. 1), Hanford (No. 3), Fresno (No. 4) and other small Central Valley cities (the Valley accounts for all the California cites on the list aside from Los Angeles): heavy doses of nitrogen oxide and hydrocarbons stemming from gasoline, chemical processing, paints and other industrial byproducts that harm the ozone and release particle pollution into the air.
A. moved to reduce surface ozone, a form of pollution caused, in part, by emissions from oil refineries.
Last year Monterrey, the country's industrial capital, clocked a higher reading than Mexico City on its index of particles smaller than 10 microns, a form of pollution that is no less dangerous than ozone.
ECONOMIST: The capital��s filthy atmosphere has improved at last
Since Mr Bush took office, the number of days when Texan cities have exceeded federal ozone standards has doubled, and Houston and Dallas currently face federal deadlines to make sharp cuts in air pollution or risk losing federal money for their roads.
But the traffic increase has slowed progress in reducing emissions further, and people in many areas still suffer from nitrogen-related air pollution, including small particulates that get sucked deep into the lungs, and ground-level ozone - a strongly irritant gas formed by the action of sunlight on reactive nitrogen.
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