EPA Particle Rules and Occupational Exposures

EPA announced its new proposed particle air quality standards. These were promptly denounced as too weak, allowing too much exposure, and contrary to the Clean Air Science Advisory Committee recommendations. BrooklynDodger will post about those scientific issues later. Let's just say that even George W. Bush thinks these standards are needed.

[Mike Leavitt, EPA administrator trained for this public health post as Governor of Utah. Historically, the first major modern study demonstrating adverse effects of particles at these levels was done in Utah. The Dodger posted on this previously.]

In short, these standards are supported by lots of epidemiology that shows increases in death, and hospitalization from respiratory and cardiac causes from fluctuations in particle levels within the range permitted by present and these proposed EPA limits. And despite canonical references to old sick people and children, it isn't only them who are effected.

EPA summarizes the proposal:

"Fine particles - 24-hour standard

• An area would meet the 24-hour standard if the 98th percentile of 24-hour PM2.5 concentrations in a year, averaged over three years, is less than or equal to the level of the standard EPA sets in its final rule (35µg/m3 under this proposal). This is the same form as the current 24-hour standard.

Fine particles – annual standard

• An area would be in compliance with the annual PM2.5 standard when the three-year average of the annual average PM2.5 concentration is less than or equal to 15 µg/m3 (or whatever level of standard EPA sets in its final rule). This is the same form as the current annual standard.

• Current fine particle standards allow some areas to average measurements from multiple community-oriented monitors to determine compliance with the annual standard. The proposed revisions also would limit the conditions under which this averaging could take place. EPA also is seeking public comment on no longer allowing averaging measurements from multiple community monitors. Inhalable coarse particles

• An area would meet the coarse particle standard if the 98th percentile of 24-hour PM10-2.5 concentrations in a year, averaged over three years, is less than or equal to the level set in the final rule (70µg/m3 in this proposal). This form will provide a more stable target for air pollution control programs by reducing the impact of unusual weather conditions, such as high wind events.
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BrooklynDodger comments: Ok, figure "fine" particles (PM 2.5) essentially the same as OSHA respirable [Count distribution would vary based on source; fine particles in environment tend to be agglomeration of combustion ultrafines, some manufacturing processes are energetic enough to mechanically generate some bigger smaller particles]. And "coarse" particles (PM 2.5 - PM 10) are essentially the same as OSHA total. [OSHA total closed face filter and the EPA method cut off larger particles, which have a lot of mass but little of particle count.]

The 98th percentile deal on daily average means 7 or 8 days a years can exceed the limit before the area gets busted for violating the rule.

How would we convert these values into occupational levels of concern? Let's say that half the air a worker breathes is breathed at work. That's conservative, since about 40% of waking hours are at work, but people breath a lot more at work than at leisure, and lot more awake than asleep.

For respirable particles, the proposal would translate to 70 micrograms six days a year, [ok, 100], and 30 micrograms averaged over the year. [Should be added to the community level for health protection.]

For total particulate, the proposal would translate to 140 micrograms, 6 days a year. Outside of grinding or sanding operations, it's likely most of total is really respirable or smaller.