Analysis: Elusive Particles of Truth: EPA’s Proposed PM 2.5 Regulations

Published November 1, 2006

This may come as a surprise, but air quality is improving in the United States. By all measures, air pollution is falling … at the same time our economy, population, and energy use are growing.

According to the U.S. Environmental Protection Agency (EPA), between 1970 and 2004, gross domestic product increased 187 percent, vehicle miles traveled increased 47 percent, and the U.S. population grew by 40 percent. Yet over that period, total emissions of the six principal air pollutants dropped by 54 percent.

But despite more than three decades of continued air quality improvement, and without compelling evidence of the need to do so, EPA wants to regulate a certain type of pollution–particulate matter–more strictly than ever.

Because air pollution controls are costly, this means EPA is considering requiring state and local governments, as well as consumers themselves, to devote precious resources to protect human health against a perceived problem even when the best available science does not support EPA’s proposed actions.

Tighter Standards Proposed

In 1997, EPA revised the National Ambient Air Quality Standards (NAAQS) for particulates to create a new standard for fine particulate matter (PM 2.5). Even as states are working to comply with those rules (the deadline for compliance is 2010), EPA on December 20, 2005 proposed a new rule to establish new standards for fine particles.

EPA is proposing to lower the current 24-hour standard for PM 2.5 from the current level of 65 micrograms per cubic meter to 35 micrograms per cubic meter.

If the rule is finalized, this would require states to figure out how to reduce particulate matter beyond EPA’s 1997 particulate matter rule, beyond the sulfur dioxide (SO2) and nitrogen oxides (NOX) emissions rule, and beyond EPA’s 2005 Clean Air Interstate Rule.

According to EPA’s own estimates, this will cost billions of dollars.

Particulate Matter Defined

What is fine particulate matter? In a word: dust. Specifically, it is very, very, very, small particles of dust.

This dust is made of particles of matter up to 2.5 microns in diameter (a micron is one-millionth of a meter). To have an idea of how small PM 2.5 is, the letter “i” in typical newsprint measures 400 microns across.

There are hundreds of types and sources of particulate matter, originating from both natural and manmade sources. Any activity that involves combustion or generates dust releases particulate matter into the air.

Natural sources of particulate matter include volcanoes, forest fires, water mist, and wind lifting dust off dry earth. Humans create particulate matter when we crush rocks or burn things such as wood, coal, or gasoline. PM 2.5 can also form through chemical reactions and droplets in the atmosphere.

EPA’s Rule Significant

EPA’s proposed tighter rule for PM 2.5 matters because it will be costly and will likely not result in any health benefits. According to the consulting firm Environmonics, national compliance with EPA’s proposed PM 2.5 regulation would cost between $20 and $60 billion a year–on top of the $13 to $20 billion in costs for nationwide attainment at the current standard.

Not only would it be costly to meet the requirements of the new regulation, but when EPA designates an area as a non-attainment area under the Clean Air Act, it discourages industry from moving in and locating in those areas. Also, a non-attainment designation makes it more difficult for existing industries to expand, costing even more jobs in the local economy.

As if that were not bad enough, non-attainment areas lose federal highway and transportation dollars.

Regulations Damage Health

In addition to the detrimental effect on jobs, EPA’s proposed tightening of the PM 2.5 standard will also likely have a detrimental indirect effect on people’s health. For example, as Harry Alford, president of the National Black Chamber of Commerce, has stated, “The biggest health risk to African Americans anywhere, is poverty.”

Higher costs, imposed because of pollution controls, will ultimately be paid by people in the form of higher prices, lower wages, and fewer choices. When people have higher incomes they spend a portion of the increased income on things that improve their health, such as better health care, safer cars, and healthier food. Poorer people do fewer of these things, and as a result, their health suffers.

Risk experts estimate that every $17 million in regulatory costs leads to one additional death. In other words, if EPA’s new PM 2.5 rule costs $60 billion a year, statistics say it will cost 3,500 lives because of the costs it imposes on society.

The most important point is that regulations are not pure risk-regulation exercises, but require society to make tradeoffs.

Because a new PM 2.5 regulation would be so costly, EPA needed to present some solid evidence for why this rule should be imposed on Americans. But EPA’s justifications for its proposed rule are weak.

Problems with EPA’s Studies

In crafting its proposed PM 2.5 rule, EPA staff relied exclusively on observational epidemiological studies to show the purported cause-and-effect relationship between PM 2.5 and health. Some studies show a small correlation between particulate matter and premature mortality after controlling for confounding factors.

This methodology implicitly assumes the researchers can and have controlled for all of the possible externalities (confounding factors) that would influence health. Such studies tend to overstate the effects the researchers are trying to find.

EPA relies heavily on an American Cancer Society (ACS) study and the Harvard Six Cities study. But a follow-up and reanalysis of the ACS study by the Health Effects Institute found some strange results. They found that PM 2.5 kills those with no more than a high school degree, but not those with at least some college education; it kills men, but not women; and it kills the moderately active but not people who are very active or sedentary.

These results are bizarre if we are to believe the ACS study has controlled for all of the factors that could influence health. These results suggest there are other factors at play and that the health effects are not necessarily the result of PM 2.5.

This is not the only problem with the ACS study. When the Health Effects Institute controlled for people moving into and out of cities, the apparent effects of PM 2.5 declined by two-thirds and became statistically insignificant. This suggests the health effects EPA is trying to attribute to PM 2.5 could be better explained by things that cause people to move, such as economic factors.

The Harvard Six Cities study has similar problems. It found PM 2.5 was not associated with increased mortality for people with more than a high school education. Again, this result is bizarre if we are to believe that PM 2.5 itself is a killer.

EPA’s Claims Contradicted

A recent review of toxicological and clinical studies, published in Regulatory Toxicology & Pharmacology, found:

“Toxicologic data on typical forms of pollution-derived PM strongly suggest that current ambient concentrations in the U.S. are too small to cause significant disease or death. We review here the results of inhalation studies using concentrated ambient particles, diesel engine exhaust particulate matter, and sulfate and nitrate salts, and find no evidence that moderate concentrations are lethal. The expectation that lives will be saved by reducing ambient PM 2.5 in the U.S. is not supported by the weight of scientific evidence, although other bases for regulating PM may be justifiable.”

Unreliable Experiment Used

Even clinical studies that appear to lend support to EPA’s claims of the dangers of PM 2.5 at normal ambient concentrations do not stand up to scrutiny.

The Journal of the American Medical Association (JAMA) published a study in December 2005 that claimed to show PM 2.5 at current ambient levels harm Americans. The study asserted current ambient levels of PM 2.5 are associated with heart disease. But the report itself showed the results were not statistically significant.

Furthermore, to find any effect caused by particulate matter, the authors used laboratory mice that were specially bred to be susceptible to heart disease.

Air pollution expert Joel Schwartz explained the problem of using these mice:

“The very reason for using these grossly unrealistic mice to study PM 2.5 is that PM 2.5 does not kill regular mice or other animals at concentrations relevant to real-world exposures. …

“[I]f you design an artificial mouse that can’t regulate its fat or cholesterol levels, it isn’t any surprise that even a minor environmental insult can cause it some health problems. But this doesn’t tell you much about the effects of low-level air pollution on regular mice or on people.”

Study’s Results Self-Contradictory

In fact, it is easy to assert the JAMA study actually finds PM 2.5 is not dangerous at current ambient levels. As Schwartz explained:

“PM 2.5 has such minute health effects that to even get PM 2.5 to cause an increase in heart disease you need mice specially engineered to have unrealistically stupendous cholesterol levels, you have to feed them a high-fat diet, and you have to expose them to unrealistically high acute doses of PM 2.5 five days a week, every week, for a quarter of their lives. Based on the JAMA mouse study, the current PM 2.5 NAAQS are health-protective with plenty of room to spare.”

This quick review is by no means a complete catalogue of the problems with the studies EPA relies on for its PM 2.5 rule. Schwartz has more information in his Comments on EPA’s Proposed Rule, National Ambient Air Quality Standards for Particulate Matter, and a number of industry groups contributed to very statistically sophisticated comments to EPA in a paper titled, Comments on Behalf of Industry Trade Associations on EPA’s Transition to New or Revised Particulate Matter National Ambient Air Quality Standards, Advance Notice of Proposed Rulemaking.

Particulate Matter Variables

Even if we assume the EPA-cited studies have no problems and PM 2.5 is dangerous at current ambient levels, we should not assume all kinds of particulate matter are equally dangerous, as EPA assumes in its proposed rule.

In 2004, the National Research Council wrote, “In the committee’s judgment, that assumption greatly oversimplifies complex biological phenomena that are influenced by PM and other pollutants. There are numerous physical and chemical characteristics of particles that are potentially relevant to their toxicity; however, to date, there is little information on the relationship between health outcomes and specific particle properties or source types.”

In short, EPA should know which particles are hazardous, if any, before regulating. Anything else will be overly broad regulation.

The extreme cost of the regulations, coupled with the shaky science upon which the proposed rule rests, should give EPA pause in the current case. EPA should not regulate particulate matter more stringently unless it has new, compelling evidence of harm at current ambient levels.

Daniel R. Simmons ([email protected]) is director of the Natural Resources Task Force of the American Legislative Exchange Council.

For more information …

Joel Schwartz’s Comments on EPA’s Proposed Rule, National Ambient Air Quality Standards for Particulate Matter, published April 17, 2006, is available through PolicyBot™, The Heartland Institute’s free online research database. Point your Web browser to and search for document #19762.

Comments on Behalf of Industry Trade Associations on EPA’s Transition to New or Revised Particulate Matter National Ambient Air Quality Standards, published July 10, 2006, is also available through PolicyBot™. Search for document #19763.

Research Priorities for Airborne Particulate Matter: IV. Continuing Research Progress (2004), National Academies Press,