Dust Regulation Is Inappropriate under the Clean Air Act

NCBA Staff Contact: 

Tamara Thies, Chief Environmental Counsel
202-347-0228

tthies@beef.org

Every five years, the EPA is required to review scientific studies associated with “criteria pollutants” regulated under the National Ambient Air Quality Standards (NAAQS) of the Clean Air Act to determine if the pollutant is regulated appropriately.  One of the criteria pollutants is particulate matter (PM, which includes dust).  The NAAQS is a health-based standard.  In other words, Congress determined that in order to regulate a pollutant under the NAAQS, scientific studies must show that the pollutant causes adverse health effects.  Conversely, if scientific studies do not show that a pollutant causes adverse health effects, it is not supposed to be regulated under the NAAQS.  The Clean Air Act, according to the U.S. Supreme Court, requires that the NAAQS be set at a level “not lower or higher than necessary to protect public health.”              

Prior to 1997, the EPA regulated PM with a standard of 150µg/m³ which applied to all PM in the size range of ten microns or smaller (PM10).  In 1997, the EPA decided to separate particles for regulatory purposes based on their composition and size since it was believed that these factors make a difference as far as health effects are concerned.  “Fine” PM (PM2.5) formed primarily by combustion or chemical reaction of gases falls in the size range of 2.5 microns or smaller.  “Coarse” PM (PM10) formed by mechanical processes consisting of minerals, crustal material and organic debris, i.e. dust, falls in the size range of 10 microns and smaller.  In 1997, the NAAQS for PM2.5 was set at 65µg/m³, the NAAQS for PM10 was retained at 150µg/m³.

The fact is coarse PM emissions have never been demonstrated to cause adverse health effects at ambient concentrations.  That is why, over the last more than 30 years, the EPA has excluded these dusts in making determinations of ambient compliance, or has chosen not to enforce the standard against agriculture and other “fugitive” dust sources.  If the standard were enforced, examples of agriculture dust that would be regulated include dust produced by tilling soil, cattle movements in feedlots, driving on unpaved roads, planting and harvesting crops, and feed mixing, among others.  

NCBA asked Yale School of Medicine epidemiologist and toxicologist Dr. Jonathan Borak to assess the quality of the studies on which the EPA was relying to decide whether regulation of dust was warranted.  His conclusion was that the studies do not provide a scientific basis for regulation of dust in urban or rural areas.  NCBA adopted this position and argued it throughout the process.   

Regardless of the lack of scientific justification, in 2006 the EPA issued a proposed rule that tried to build a case for regulation of coarse PM in urban areas, while admitting throughout the document that the evidence linking coarse PM to human health effects is very weak.  In fact, the EPA acknowledged in the proposed rule that the scientific uncertainty is “too large to use the reported air quality levels directly as a basis for setting and specific standard level.”  The EPA generally proposed to regulate urban-like dust, and to exclude dust from agricultural sources.   The proposed exclusion of agriculture dust was very good news for NCBA, and was evidence that EPA had listened to and agreed with our arguments.

Environmental groups, state governments, and others, however, strongly opposed excluding agriculture dust from regulation under the NAAQS.  They argued that the NAAQS is a national standard that must apply equally throughout the United States; and that it would be unfair for states with nonattainment areas not to be able to control all sources that contribute to the nonattainment status, among other arguments.

Unfortunately, in spite of the fact that there is no scientific basis for regulating coarse PM, the EPA decided to continue to regulate PM10 at 150µg/m³ with no agriculture exclusion in a final rule released in October 2006.  The final rule contains favorable Preamble language stating that because evidence of adverse health effects caused by agriculture dust is so weak, states should focus on regulating dust in urban areas instead of rural areas, among other things.  But the Preamble also states that “the substantial scientific uncertainty regarding the health effects associated with different components and mixes of coarse particles, the large population groups potentially exposed to non-urban [dust] and the nature and degree of health effects at issue, have convinced the Administrator that it is inappropriate to [exclude agriculture dust] at this time.”  “EPA disagrees with these commenters that there is sufficient evidence to demonstrate that there are no adverse health effects from … exposure to [dust] in non-urban environments.” “EPA … concludes that … some protection from exposure to [dust] particles is warranted in all areas.”  So on the one hand the Preamble urges states to concentrate on regulating dust in urban areas, but undercuts that suggestion by declaring there is no justification for excluding the regulation of dust from anywhere.  EPA based its decision on the “precautionary principle” instead of good science.

Apart from the lack of scientific justification, NCBA is concerned about the regulation of dust because the best evidence available indicates that well-controlled cattle feeding operations produce PM10 ambient concentrations of several hundred micrograms per cubic meter.  Violations occur regardless of the fact that feedyards use best management practices (sprinkling pens with water and scraping) to control dust.  States and private citizens can force operations to comply with the PM NAAQS which must be met at the property line of each individual operation without any exception or variance, even those based on economic or technical infeasibility.  NCBA supports dust control measures and our producers carry them out every day of every year.  But the imposition of a NAAQS would require that dust must be controlled to an unattainable level, possibly requiring selling cattle to comply.  In addition, experience with NAAQS reviews indicates a high likelihood that future reviews will result in a tightening of the standard, something that would be harmful to cattle operations since many operations are unable to comply with the current standard.  Finally, NCBA is concerned about the fact that regulation under the NAAQS gives the public the impression that dust from cattle operations causes disease or premature death when there is no scientific evidence that this is true. 

It is for the above reasons, among others, that NCBA appealed the final rule to the DC Circuit Court of Appeals.  No date has been set for oral argument which is expected to occur during 2008.