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Once inhaled, these particles can affect the heart and lungs and cause serious health effects.  * The EPA has itemized numerous methods to control PM emissions including paving unpaved roads, swapping out wood-burning stoves for propane logs, and installing particle filters/collection devices on engines and factories.   * In 2010, before the EPA made the clean air standard for PM2.5 stricter, the EPA estimated that 6% of the U. population lived in counties that did not meet the EPA’s clean air standards for PM2.5. * The population most susceptible to elevated SO2 levels is asthmatics.Among healthy non-asthmatics, SO2 does not typically affect lung function until concentrations exceed 1,000 parts per billion (ppb).EPA’s task is to establish standards that are neither more nor less stringent than necessary for these purposes.In so doing, EPA may not consider the costs of implementing the standards.  * The population most susceptible to elevated CO levels are those with coronary artery disease. Coronary artery disease is typically caused by the build-up of cholesterol-containing deposits in major arteries. * The primary study used by the EPA to set clean air standards for CO was conducted on subjects with moderate to severe coronary artery disease, more than half of whom previously had heart attacks.The study’s authors attributed these higher rural ozone levels to manmade ozone precursors blowing in from the city and to a “scavenging reaction” that limits ozone levels in urban areas.The authors did not address the prospect that the higher ozone levels in rural areas were related to natural sources.   * Carbon monoxide levels are generally higher in homes than outdoors, and even greater levels of CO have been measured in rooms where people are smoking, indoor ice rinks (from ice resurfacing machines), homes with attached garages in which cars are idled, and indoor arenas where motocross races and tractor pulls are held. * In nations where modern energy is unavailable or prohibitively expensive, people tend to burn more wood, animal dung, crop waste, and coal in open fires and simple home stoves.
This is called bioaccumulation, and it occurs because certain pollutants are not easily excreted or metabolized. * Bioaccumulative substances are often passed upwards through aquatic food chains, and thus, concentrations of such chemicals tend to be higher in creatures near the top of these food chains, such as salmon and trout.  * PCB’s are a group of bioaccumulative chemicals that were banned from production in the U. Due to bioaccumulation, the concentrations of dioxins in fish can range from hundreds to thousands of times higher than the ambient concentrations in waters that the fish inhabit. * During 2000 through 2003, the EPA conducted a random survey of fish contamination levels in 500 of the 147,000 lakes and reservoirs in the continental United States.The study’s lead author stated: No matter what soil I grew them in, they always grew twice as large in New York City. In the country, the trees were about up to my waist.In the city, they were almost over my head—it’s really dramatic.To establish a baseline, participants engaged in mild exercise on a treadmill while measurements were made of the time it took to develop chest pain and a specific electrocardiogram signal that indicates insufficient oxygen supply to the heart.Subjects repeated this test after resting for about an hour while being exposed to elevated CO levels ranging from 42 to 202 parts per million (mean of 117).