Particulate Matter Regulatory Controversies and the Maryland Nurses Association Study

Emissions from Maryland's six largest coal-burning power plants contribute to 700 deaths each year, including 100 deaths in Maryland, according to a Harvard University study sponsored by the Maryland Nurses Association. The MNA supports a bill in the state legislature that would require power plants to sharply reduce pollution over the next decade.

The investigators from the Harvard School of Public Health used published emissions data of oxidant gases (oxides of nitrogen and sulfur dioxide) and fine particulate matter (PM2.5) for the six coal-fired power plants, estimated the concentrations in air surrounding those plants using an air dispersion model, and combined those modeled concentrations with published concentration-response functions (responses being mortality or morbidity as reflected in hospital admissions) and population statistics to estimate the health impacts.

This study concluded that the total contribution to ambient PM2.5 concentrations in Maryland is around 0.2 to 1 ug/m3. While it’s a small contribution to the overall PM2.5 concentrations, which range from 12 to 17 ug/m3, the investigators concluded there may be important public health considerations associated with that increment. Relatively small reductions in concentrations could yield substantial public health benefits. For example, the investigators project the impacts to Maryland, and nationally (i.e. the surrounding six states such as Pennsylvania and New York) from emissions from the six power plants:

Scaling to current population data and aggregating across all six power plants, I estimate an annual impact in Maryland on the order of 100 premature deaths, 4,000 asthma attacks, and over 100,000 person-days with minor restrictions in activity. The corresponding annual national impacts from the six power plants are approximately 700 deaths, 30,000 asthma attacks, and nearly 800,000 person-days with minor restrictions in activity.

Using standard economic values corresponding to health endpoints, the investigators conclude that the annual economic burden would be on the order of hundreds of millions of dollars within Maryland and billions of dollars nationally. There are uncertainties in these estimates, driven in large part by the economic value assigned to a premature death (i.e. the so-called “six million dollar man”), but they are close enough for purposes of discussing the relative merits of various control decisions. The report observes that most of the remaining fine particulate matter comes from numerous other sources such as mobile source emissions and out of state power plants, which may be more difficult for the state of Maryland to control (yes, I can hear the power companies now, “why is that our problem?” But there’s a political solution to the public health problem, if everyone works together). According to the American Lung Association of Maryland, there are feasible control technologies to reduce power plant emissions; much of the fine particulate matter impact is related to sulfur dioxide emissions from coal burning (sulfur dioxide oxidizes in the atmosphere to form particulate sulfates), which can be addressed using flue gas desulfurization.

The publication of this study comes on the heels of EPA’s proposed revisions to the National Ambient Air Quality Standards (NAAQS) for particulate matter. Over the past several years, EPA has been conducting a scientific review of the PM NAAQS, a concentration in air that is intended by Congress to protect public health with an ample margin of safety. EPA’s review has been overseen by the Clean Air Scientific Advisory Committee or CASAC, a panel of EPA’s Science Advisory Board. According to the LA Times, the EPA has chosen to ignore the advisory committee’s recommendations, apparently an unprecedented act. In addition, one participant in the standard-setting process noted that the Office of Management and Budget had extensively marked up the draft standard, revisions that did not receive any public comment.

EPA proposed to slightly tighten particulate matter standards, but to a lesser extent than recommended by CASAC. The agency also proposed to exempt rural areas and mining and agriculture industries from standards governing larger coarse particles, and declined to adopt CASAC’s proposed welfare standards (i.e. for reduction of visible haze). According to the LA Times, some panel members called the actions on the part of EPA Administrator Stephen Johnson "egregious" and said his proposals "twisted" or "misrepresented" their recommendations. Following a teleconference Friday February 3, 2006, the committee members will urge Johnson to reconsider his proposals. It was the first time since the committee was established under the Clean Air Act nearly 30 years ago that it has asked the EPA to change course, according to EPA staffers and committee members. A brief description of this controversy is in a statement issued by the American Lung Association, following the February 3, 2006 teleconference held by CASAC.

The NAAQS thing isn’t news – there was a squabble over it at Political Animal a couple of weeks back (true to form though, that post and the comments provided little of a cogent analysis). The CASAC and EPA Administrator (and OMB for that matter) are arguing over fairly small differences in PM concentrations in terms of a standard; though those fairly small differences appear to have significant public health consequences. I’ve been drafting a post about it, which has stalled a bit because I’ve had to go back and refresh my memory about the relative significance of the 24-hour and annual average NAAQS to do it justice. It isn’t the easiest thing to write a readable analysis of a highly technical topic and still have it be fresh news.