Vermonters for a Clean Environment Weekly Update

Monday, October 16, 2000

Particulate Matter

by Guest Columnist Dian Deevey.


Dear Activists Challenging New Power Plants:

My name is Dian Deevey. I am a retired atmospheric scientist. Before retirement, I conducted basic research on the origin and fate of atmospheric particulate matter, and for many years acted as a consultant with the EPA group responsible for all studies of atmospheric particulates, including their sources, composition, distribution, and health effects. Since retirement I have remained in contact with my former EPA colleagues, and have continued to follow developments in this field.

I have a summer home in Columbia County. For the last two years I have focused much of my extra time on the scientific and regulatory issues associated with particulate pollution from new industries in the Hudson Valley.

I write to bring to your attention a serious health hazard associated with the very fine particles less than 2.5 microns in diameter (called "APM2.5") that will be released to the atmosphere by new power plants and other industrial facilities, should they be built and operated.

The PM2.5 hazards are serious ones. They should be considered in detail by siting boards reviewing the new power plants now planned for NYC, Staten Island, and the Hudson Valley. Their adverse health effects include increases in the number and severity of asthma attacks in children and adults, increases in episodes of breathlessness and other kinds of distress in people suffering from chronic bronchitis, emphysema and other pulmonary diseases, leading to more ER visits and to hospitalization. There is abundant evidence that heart attacks and even premature death in people with pre-existing cardiovascular disease are triggered by quite moderate increases in atmospheric levels of particulate matter.

While those at greatest risk are children and the elderly, large numbers of individuals of normal health may experience frequent and more serious episodes of flu, colds, and other respiratory diseases. (Sources for information about health effects and other issues raised here are included at the end of this letter.)

The present situation can be summed up briefly:

Natural gas-fired power plants are a potent source of extremely hazardous tiny particles 2.5 microns or less in diameter (PM2.5). All of the particulate matter produced by the gas fired turbines of power plants will be less than 2.5 microns in diameter. In fact, all of it will be less than 1 micron in diameter, and consist largely of organic compounds referred to as products of incomplete combustion (PICs). Some hazardous trace metals will also be released along with the PICs.

The power plant siting bill (Article X) requires that all public health hazards that might result from the operation of power plants under consideration for certification be carefully considered.

The PM2.5 standard was not considered by the siting board that certified the PG&E plant in Athens. None of the intervenors in the case knew that particles in this size range had been identified as a serious health hazard, nor that all the particulate matter from the gas-fired turbines would fall in this size range. Representatives from the Department of Environmental Conservation and the Department of Health who testified and submitted affidavits during the hearings failed to advise the siting board of this serious potential health hazard. These two agencies are specifically charged with providing information about health and air quality to the siting board.

PM2.5 is a hazard that should be brought up to the power plant siting board in future proceedings. Parties to the actions need to be fully aware of this pollutant and its impacts.


Particulate matter is one of the several pollutants present in the dirty urban air that has long been known to be associated with acute and chronic health problems. Beginning in 1971, the EPA has issued and New York has enforced pollution standards to keep the amount and kind of particulate matter in the atmosphere below the level known to be dangerous to health. These standards are subject to detailed review every 5 years.

Particulate matter is produced as smoke and soot during the combustion of fossil fuels. Some Asecondary@ particulate matter is produced in the atmosphere by spontaneous chemical reactions among pollutant gases such as sulfur dioxide, oxides of nitrogen, and volatile organic matter. Natural sources of particulate matter include windblown dust, sea salt particles produced in surf at coastal sites, and forest fires.

The EPA's early 1971 standards for atmospheric particulate focused on total suspended matter (ATSP@) which comprises particles up to 40 microns in diameter. (For comparison, the average human hair is about 70 microns in diameter). In 1987, the EPA revised its regulations to focus on particles less than 10 microns in diameter ("APM10") because overwhelming evidence had shown that the smallest particles in the atmosphere caused most of the harm to humans breathing them.

In 1996, the EPA again announced new standards, this time focusing on even smaller particles 2.5 microns or less in diameter (PM2.5). Evidence emerging from hundreds of studies has shown that these tiny particles are chiefly responsible for the most serious adverse health impacts associated with pollution. When inhaled, PM2.5 penetrates deep into the human lung, where the particles and the toxic materials attached to them remain lodged. The new standards for PM2.5 have not yet been implemented.

Many scientific studies have confirmed that the existing PM10 standards do not protect public health. In June 2000, a major study confirmed that high rates of premature deaths among the elderly suffering from heart trouble and other health problems are seen in response to very moderate increases in PM10 levels, even though the latter may be well below the Asafe@ threshold level set in 1987. Similar conclusions have been supported in many other epidemiological studies. Other research has shown that PM2.5 is the likely culprit in a wide range of adverse health impacts, and that no other pollutant measured seems to exert so strong an influence.

But until the new PM2.5 standards proposed by EPA are implemented sometime after 2005, new pollution sources need only satisfy the loose 1987 standards to obtain an air permit from DEC. The Clean Air Act which prescribes state air permitting requires only that existing standards be enforced.

One reason for this delay is that the EPA's PM2.5 standard were challenged in court by the American Trucking Association and a large number of corporations, industry representatives and some states which are home to major polluters. A Federal Appeals Court decision favoring the plaintiffs remanded the PM2.5 standard back to the EPA, and allowed the inadequate PM10 standard to stay in effect. The case will be argued before the Supreme Court on November 8, 2000.

PM2.5 and Power Plant Siting

The New York siting board reviewing each new plant application has to decide whether that plant will be "...compatible with public health and safety..." According to representatives of the Public Service Department, Article X requires that if there is any health or other environmental risk associated with any pollutant from a proposed power plant, that risk must be very fully considered by the board. This is true even if the proposed plant can satisfy all the requirements of the Clean Air Act, including the existing regulations for PM10 levels.

The PM2.5 hazard was not considered by the siting board that approved the power plant in Athens. No party brought up the issue, and neither the DEC nor the DOH volunteered any information about it. No one questioned these or any other witnesses about PM2.5. The board was told only that PM10 particulate emissions from the new plant will comply with existing standards. Examination of the record confirms that the board was informed (in error) that compliance with the PM10 standard implies protection of public health and safety.

Natural gas-fired power plant emissions are cleaner than those from coal-fired power plants. According to data published by EPA, gas-fired turbines produce only about 10% as much particulate matter as the average coal fired plant that uses the best pollution control technology, when compared on an energy-equivalent basis. The particulate matter that is emitted from the stacks of coal-fired power plants contains many highly toxic trace metals and other toxic constituents not found in the stack gases of plants using natural gas. Nevertheless, particles produced by natural gas combustion are not benign. They contain a large suite of toxic organic compounds as well as some toxic metals. Furthermore, all the particulate matter produced by natural gas combustion is less than 1 micron in diameter, which puts these emissions at the lower end of the PM2.5 size range, believed by many to be the more dangerous size range.

Particles of one micron and less in diameter are known to be the most effective in producing haze and reducing visibility.

In general, if one has a choice between natural gas and coal as a fuel for producing electric energy, natural gas is the way to go. But if it is not a matter of swapping Natural gas-fired power generation for coal-fired power generation, then a different posture is appropriate. Adding a source of particulate emissions to the dirty air already present in most of southeastern NY should be vigorously opposed by citizens who are concerned about the health of the affected populations.

Some idea of the possible effect of power plant particulate emissions can be obtained from considering the analysis of the impact of the particulate emissions from the Athens plant on the surrounding air. Using simple dispersion models, the applicant concluded that the plant would raise the annual average level of particulate matter by 1 to 3 micrograms per cubic meter of air. The lower figure assumes an uneven land surface that favors dispersion, while the higher figure assumes flat terrain that can lead to stagnant air and an accumulation of local emissions. Short- term increments in particulate matter could range up to about 20 micrograms per cubic meter or more, depending on the terrain and the short-term meteorological conditions.

The amount of PM released from a large power plant like the 1080 Megawatt Athens plant depends upon the percentage of the time it operates at peak capacity, as well as the emission rates of the individual power-generating turbines it operates. For the Athens plant, emission rates listed in the air permit would correspond to a maximum of 448 tons per year of particulate matter from the gas-fired turbines, and 44 tons per year from the oil-fired turbines. All of the particulate matter from the gas-fired turbines will be less than one micron in diameter, and therefore fall within the PM2.5 category. According to EPA data, 77% of the particulate emissions from oil-fired turbines will be PM2.5.

No power plant operates at peak capacity 100% of the time. The Athens' air permit requires it to operate the gas-fired turbines at least 75% of the time. This corresponds to a minimum total of 336 tons per year of very fine particulate matter from these turbines. Seventy-five percent of the maximum emissions allowed from the oil-fired turbines would inject another 25 tons per year of PM2.5 into the local atmosphere. The resulting total of about 360 tons of PM2.5 per year for the 1080 megawatt may be used as a basis for rough estimates of the PM2.5 emissions from other natural gas fired plants. The emission rate is proportional to the Megawatt capacity of the plant, and the percentage of time it operates in each year.

Dian R. Deevey
PO Box 30
Canaan NY 12029

Additional Information

A brief discussion of my sources for the information in this letter, and some useful URLs follows.

Health hazards of PM2.5 and inadequacy of the existing PM10 standard. A FACT SHEET EPA handed out when they promulgated the new standards in 1997 is a good source for a brief summary of the health hazards of PM2.5. It is called "Health and Environmental Effects of Particulate Matter". It is at:

Another useful brief statement is at

Another good source is the Executive Summary in the first chapter of the draft of the Air Quality Criteria Document, a huge compilation containing reviews of hundreds of studies relevant to the establishment of an PM2.5 standard. These AQCDs are released every 5 years, and a draft on one to be released in December is available on the Internet. Most of the health studies are discussed in Volume II. Links to this document are available at:

The AQCD summarizes many epidemiological and other studies showing the inadequacy of the existing particulate matter standards. An additional very important study confirming this conclusion was released in June of this year. This is the National Morbidity, Mortality, and Air Pollution Study, Part II. It is an extremely exhaustive and detailed evaluation of the relationship between measured PM10 levels and the levels of other pollutants, and mortality from a variety of causes and hospitalizations among residents on Medicare 65 years of age or more. This study showed that even very modest increases in PM10 levels result in increases in death rates among this group. Across the country, the increase in death rates averaged 0.5 percent for every increase of 10 micrograms per cubic meter. Since increases of this magnitude or greater occur many times each year, the cumulative impact is very large. The impact was largest among cities in the Northeast, including three cities in New York state. The New York Times published an article describing the major findings of this study on June 28,2000. The full report can be found at:

Emissions data. EPA collects and publishes emission rate factors for most processes that emit pollutants into the atmosphere. These are constantly updated. Information about natural gas is in Chapter 1.4 of the basic document. Links to the current version and to new draft material can be found at:

This chapter contains a listing of the metals and of organic compounds found attached to particles produced during natural gas combustion. These may be compared to similar data for coal- and oil-fired utility boilers elsewhere in Chapter 1.

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