Dust Regulation

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 Dust Study

Overview of Dust Regulation

I. Background

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 are primarily health-based standards.  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.”  A “secondary” NAAQS considers effects of pollutants on the public’s “welfare” (i.e. the environment). Areas that do not meet the NAAQS for a particular pollutant are known as “nonattainment” areas which must get into attainment for that pollutant within a prescribed period of time.  States have primary responsibility for getting areas into attainment and for keeping them in attainment through State Implementation Plans (SIPs).                

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 or PM10-2.5 or PMc) 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 (PM10 includes the PM2.5 size fraction, PM10-2.5 subtracts out the 2.5 size fraction).  In 1997, the NAAQS for PM2.5 was set at 65µg/m³, the NAAQS for PM10 was retained at 150µg/m³.
The most recent PM NAAQS review and modification was finalized in October 2006.  At that time, EPA was concerned about possible health effects from dust in urban areas that might be contaminated with pollutants emitted from vehicles.  There were no studies showing that rural dust was a health concern.  Consequently, the agriculture sector pushed hard to exclude rural dust from regulation.  Unfortunately, EPA decided to continue to regulate all PM10 at 150µg/m³.  The final rule contains favorable Preamble language stating that because evidence of adverse health effects caused by rural 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 . . . 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.  Rural dust that is subject to regulation under the NAAQS includes dust produced by tilling soil, cattle movements, driving on unpaved roads, planting and harvesting crops, and livestock feed mixing, among others.  

Agriculture located in arid parts of the US often has a difficult time complying with the PM NAAQS.  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.   Experience with NAAQS reviews indicates a high likelihood that future reviews will result in a tightening of the standard.  In addition, dust regulation under the NAAQS gives the public the impression that dust from agriculture operations causes disease or premature death when there is no scientific evidence that this is true.

II. Current Dust NAAQS Review

The EPA is currently in the process of its next review of the PM NAAQS.  It claims the 2006 rule, particularly the PM2.5 standard, was not sufficiently protective of the public’s health.  In December 2008, EPA released its First Draft Integrated Science Assessment (ISA) which essentially found that evidence of the need to regulate coarse PM (PM10-2.5) was “inadequate.”  In contrast, the EPA’s 2nd Draft ISA, released in August 2009, appeared to rely on one flawed July 2009 study, by Zanobetti and Schwartz, to conclude that evidence of health effects from PM10-2.5 is no longer “inadequate” but “suggestive” of adverse health effects.  The flawed Zanobetti and Schwartz study found adverse health effects from PM10-2.5 at 12-15 mg/m3 (a ten-fold more stringent level than the current PMc NAAQS of 150 ug/m3)!  The final ISA, with the same findings, was released in December 2009.

On July 8, 2010, the EPA released the final Quantitative Health Risk Assessment for Particulate Matter (June 2010).  In that document, the EPA acknowledges that the science on coarse PM is so uncertain that it could not conduct a quantitative risk assessment.  Specifically, the EPA concludes that “significant limitations in both the health effects data base and the current PM10-2.5 monitoring network continue to exist and that the currently available information do not support conducting a quantitative risk assessment for PM10-2.5 at this time . . .” Id. at 2-7.

On April 20, 2011, EPA released the final Policy Assessment (PA) document on EPA’s review of the PM NAAQS which sets forth staff recommendations to the EPA Administrator regarding potential revisions to the PM NAAQS.  The PA acknowledges that uncertainties in the underlying science support:  “either retaining or revising the current 24-hr PM10 primary standard, depending on the relative weight placed on the evidence supporting associations with PM10-2.5, the uncertainties associated with this evidence, and the ISA conclusions that the evidence is only “suggestive” of a causal relationship (i.e. rather than “causal” or “likely causal”) between short-term PM10-2.5 and [health effects].”
The PA suggests that the Administrator would be justified in either retaining the current dust NAAQS of 150 µg/m³ with an allowance of only one violation per year to remain in compliance (i.e. the “99th percentile form”), or in revising the standard to between 65-85 µg/m³ with an allowance of 7 violations per year to remain in compliance (i.e. the “98th percentile form”).  EPA claims these two standards are essentially equivalent in terms of public health protection and is interested in proposing the latter standard in an effort to get away from having to designate areas as nonattainment in the event of two dust spikes in any given year.

The reality is that while the latter standard may not pose a compliance problem in urban, non-dusty areas of the US, when it comes to arid, rural, agricultural areas of the US, the latter standard would be devastating since it would essentially be twice as stringent as the current standard.  Since EPA claims its health concerns are tied to urban dust, and not rural dust, it makes little sense to adopt a standard that may enable urban areas to remain in attainment but throw rural areas into nonattainment needlessly.

In an effort to discover and document the effect the potential new standard would have on attainment/nonattainment designations across the US, NCBA contracted with Dr. John Richards, Ph.D., P.E. of Air Control Techniques, Cary, North Carolina, to study the issue.  The study looked at 382 of the 990 PM10 (dust) monitors operating in the United States from 2007-2009, primarily located in the West, Southwest and Midwest, and concluded that the existing and anticipated dust standards are NOT equivalent to one another when it comes to ability to comply.
Specifically, the study concludes that EPA’s expected revised standard would put some rural areas that are currently in attainment in the following states into nonattainment: Arizona, Colorado, Iowa, Missouri, Montana, Nebraska, New Mexico, Texas, and Wyoming. In addition, areas that are currently in nonattainment in California, Nevada and Utah would stay in nonattainment.  All the rest of the areas on the attached map below would be pushed to the brink of nonattainment where slight changes in weather patterns could throw the areas onto nonattainment.

III. Talking Points

  • In 2006, EPA set a coarse PM (i.e. dust) National Ambient Air Quality Standard (NAAQS) of 150µg/m³.
  • EPA used the “precautionary principle” to set the standard since the science was inconclusive
  • Rural dust is nothing more than dust kicked up by cars or trucks travelling on dirt roads or a tractor tilling a field, and has long been considered to be of no health concern at ambient levels
  • Under the Clean Air Act, EPA is required to review the dust NAAQS every 5 years
  • EPA is in the process of that next review of the dust NAAQS
  • This time around, EPA has laid the foundation to impose the most stringent regulation of dust in US history.
  • The EPA is preparing to propose to regulate dust at a level that is twice as stringent as the current standard!
  • The current standard is 150 µg/m3 with a 99% percentile form (which allows only one violation per year to still remain in compliance)
  • EPA is expected to propose tightening the standard to 65-85 µg/m3 with a 98th percentile form (which allows 7 violations per year to remain in compliance)
  • EPA claims these two standards are essentially “equivalent” for health protection
  • So why do it?  EPA wants to change to the 98th percentile form in an effort to stop from having to take into consideration “spikes” in emissions that put areas into nonattainment if violations occur 
  • That’s fine if you live in an urban, essentially dust free, area of the country.  But if you live in rural America and produce food for a living it’s not fine.  Food production requires tilling soil, harvesting crops, livestock rearing, and travelling on dirt roads, all of which emit dust.
  • Dust regulation at a level that is twice as stringent as the current standard would require the designation of many more nonattainment areas than currently exist, and would be economically devastating for agricultural and other resource-based operations in this state.
  • Since health evidence does not require a revision of the dust standard, we urge the EPA to retain the current dust standard.
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-Tony Turri - California