Thursday, July 22, 2010

EPA Consideration Of Strict Coarse Particle Standard Sparks Industry Fear

EPA's latest policy assessment for its ongoing review of the agency's particulate matter (PM) ambient air standards includes a first-time proposed range of limits for a stricter coarse PM (PM10) standard, sparking fear from the mining and agriculture industries -- large sources of PM10 emissions -- that the standard would be impossible to meet.

In its second external review draft of the policy assessment for the PM national ambient air quality standard (NAAQS) review, EPA floats the possibility of a 24-hour NAAQS for PM10 in the range of 65 micrograms per cubic meter (ug/m3) and 85 ug/m3 -- much lower than the existing 150 ug/m3 standard.

However, EPA is also considering a new approach to setting the standard that would allow more exceedances of the ug/m3 limit before the agency deems an area out of attainment with the NAAQS. Environmentalists caution that this approach to implementing the standard makes it less stringent than it first appears.

The agency also leaves the door open to retaining the existing PM10 standard, depending on whether EPA opts not to take into account new data showing harmful effects on human health from PM10 exposure.

The policy assessment released July 8 is designed to “bridge the gap” between highly technical risk assessments and decisions to be taken by the agency on whether to revise the NAAQS, EPA says. The agency will take comment until Aug. 16 from its Clean Air Scientific Advisory Committee (CASAC) and the public on the policy paper, which offers proposed ranges for a NAAQS revision unlike earlier science-focused risk and exposure assessments.

EPA staff in the policy assessment cautions that there is considerable uncertainty associated with the science behind course PM risks. For example, the body of experimental human inhalation studies is relatively sparse, monitoring for course PM is less widespread than that for fine PM (PM2.5), and “very little information is available to inform weight of evidence conclusions for endpoints associated with long-term exposures.”

Despite the uncertainty, EPA staff recommends changing the PM10 standard, but cautions that “standard levels around the upper end of this range are most strongly supported by the evidence.”

The existing form of the standard permits only one exceedance of the NAAQS level in a three-year period. In the policy paper, EPA says that if it tightens the standard within its 65-85 ug/m3 range, it could switch to a so-called 98th percentile form, which would allow 21 exceedances over three years. While activists endorse a stricter PM10 standard, they are raising early concerns about the change in form.

A source with the American Lung Association (ALA) says that a new ambient PM10 standard of 85 ug/m3 using the revised form is “not really that much of a reduction” in air pollution. A NAAQS set at the lower end of the range, however, would be significantly more stringent than the existing limit.

Even with a 65 ug/m3 limit ALA would probably take issue with the proposed form. “We have had problems, historically, with the 98th percentile,” as this allows too many spikes in pollution, the source says, adding that this will likely be reflected in ALA's upcoming comments on the policy paper.

To implement the standard, states would have to craft state implementation plans (SIPs) -- air quality blueprints that detail the emission controls they will impose on sources under their regulatory control in order to cut PM10 emissions and attain the standard. Mining and agricultural operations in rural areas tend to have high levels of PM10 emissions and would therefore be likely targets for new controls in SIPs under a stricter NAAQS.

Agriculture, Mining Industry Objections

Despite environmentalists' doubts that a tighter standard would be sufficiently stringent if EPA changes the form, farming and mining groups are already alarmed at the prospect of a tougher standard in the proposed range -- regardless of the form that EPA selects. “I think that agricultural operations . . . would have a very difficult time achieving a standard set that low,” says a National Cattlemen's Beef Association source.

Farming and ranching operations can produce significant amounts of dust that contribute to PM10 formation, particularly in the West. But the source says there may be no options for cutting dust from the sector to meet a stricter standard, because farmers are already employing best management practices to reduce dust. The source says it is unclear what technology options are available to curb dust in inherently dusty regions.

Similarly, a National Mining Association (NMA) source says that the mining industry is a large source of PM10 emissions but it would be difficult to meet a stricter PM10 standard because industry is already using best management practices for controlling those emissions. If EPA tightens the PM10 standard, “we are not sure there is anything to be done about it,” the source says, adding that a standard at the stricter end of the proposed range would be a “real regulatory stretch,” with few remedies available from the industry to meet the standard.

The NMA source also highlights apparent doubts EPA staff expresses in the policy assessment over uncertainties in the science on PM10's harmful effects, saying “EPA says it would be justified in leaving the standard unchanged” if policymakers feel those uncertainties are sufficiently serious.

The ALA source, however, rejects the industry arguments and says a lack of emission control technology should not be the driver behind a NAAQS revision. The Clean Air Act requires that NAAQS be set based only on public health criteria, and the act has always been a “technology forcing” law that drives innovation, the source says.

Tighter PM2.5 Standard

The draft policy paper also reiterates earlier EPA staff recommendations to tighten the existing annual PM2.5 standard of 15 ug/m3 to a range of 11-13 ug/m3, and either retain the existing 24-hour PM2.5 NAAQS of 35 ug/m3 or revise it down to a stricter level of 30 ug/m3. PM2.5 is widely considered to present the greater public health risk, and is a more urban problem than PM10, which is predominantly an issue in rural areas.

EPA staff further recommend a tightening of the secondary [welfare-based] NAAQS for PM2.5. At present, there are secondary standards for PM set at the same levels as the primary NAAQS, but the policy assessment treats criteria for setting secondary NAAQS related to visibility separately from criteria not based on visibility.

“Staff concludes that the currently available information clearly calls into question the adequacy of the current standards,” the document says, “and that consideration should be given to establishing a new indicator based on speciated PM2.5 mass and relative humidity to calculate PM2.5 light extinction.”

EPA says that the new PM2.5 standard should use a 1-hour averaging time, considering only daylight hours with relative humidity no higher than 90 percent, and a level of PM2.5 light extinction in the range of 191 to 64 inverse megameters (Mm-1.) Light extinction is this context is PM's ability to impair visibility by scattering and absorbing light waves.

CASAC has previously said that using light extinction rather than traditional methods could be technically difficult to achieve. For example, many existing technologies for measuring light extinction are inadequate for the indicator EPA wants to use because they use the wrong wavelength of light.

On secondary effects not related to visibility effects, the policy assessment says “staff concludes that the currently available information supports retaining control of both fine and coarse particles to address PM-related effects on ecosystems and materials damage and soiling, but that there [is] insufficient information to assess the adequacy of protection afforded by the current standards.”

Further, EPA concludes that there is currently not enough information available for a NAAQS to be based on the contribution to climate change of PM or its constituents. The climate effects of PM are a new area of inquiry for the agency, but the state of the current science does not yet support regulatory action despite EPA's clear conviction, expressed in the policy assessment and earlier scientific documents, that PM does have a direct impact.

PM constituents such as black carbon, organic carbon, sulfates and nitrates all have an effect on climate, EPA acknowledges, although the relationships between these pollutants and atmospheric warming and cooling are complex and not well understood. “The current state of the science of climate alterations attributed to PM is in flux as a result of continually updated information,” the policy assessment states.


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