=======================Electronic Edition========================
RACHEL’S HAZARDOUS WASTE NEWS #373
—January 20, 1994—
News and resources for environmental justice.
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INVISIBLE KILLERS: FINE PARTICLES
Eight studies of air pollution in U.S. cities have now shown that
fine particles (the invisible soot emitted by incinerators,
automobiles, power plants and heating units) are presently
killing about 60,000 Americans each year. [1] More than a dozen
studies have, in one way or another, confirmed this relationship.
Furthermore, there appears to be no threshold, no level below
which effects disappear. This means that people are being killed
by air pollution levels well within existing federal standards.
To summarize bluntly, any increase in fine particles in the
atmosphere kills someone. The victims remain nameless, but they
have been deprived of life all the same. Mere compliance with
federal standards does not protect the public. Any increase in
the number of small particles in the air elevates the death rate.
This has obvious implications for certain technologies:
incinerators and fossil-fuel-powered machines (automobiles and
trucks, power plants and heating units). To protect public
health, these technologies must be avoided, or fitted with
expensive control equipment, or replaced by cleaner alternatives.
People have known for a long time that particles in the air can
kill. In 1952, a dense smog killed 4000 people during one week in
London, and since then no one has doubted the cause-and-effect
relationship. The question, therefore, isn’t whether airborne
particles can harm humans, but rather, how much pollution causes
how much damage, and, secondly, is there a threshold, an amount
below which no effects are seen?
Throughout the ’50s and ’60s, complacent authorities assumed
there was a threshold –some amount that was safe. However,
after 1975, a revolution took place in scientific understanding
of fine particles and health. In 1979, the National Research
Council of the National Academy of Sciences, [2] and the United
Nations, [3] both published book-length studies of the dangers of
small particles to humans. Here is the current view: humans
evolved in an environment where dust was made up of large
particles. Humans therefore evolved means for protecting
themselves against large particles. Large particles are filtered
out by hairs inside the nose, mucous membranes in the throat and
airways, and other mechanisms. However, modern combustion
machines produce small particles which pass right by these
natural protections and then enter the deep lung. In the deep
lung, air comes into contact with a person’s blood stream; this
is where oxygen passes into the body and carbon dioxide passes
out with each breath we take. Putting tiny particles of
pollution directly in contact with the surface of the deep lung
is a recipe for trouble. Because of their origin in combustion
processes, most fine particles are coated with toxic materials
–metals like lead and mercury, or toxic organics like polycyclic
aromatic hydrocarbons (PAHs). So fine particles provide a
uniquely efficient carrier, giving dangerous toxins direct entry
into the blood stream.
Armed with new knowledge, in 1987, U.S. Environmental Protection
Agency (EPA) established new, stricter standards for particles in
the air. The 1987 standard, which governs today, is expressed in
terms of small particles (also called particulate matter) that
measure 10 micrometers or less in diameter. (A meter is 39
inches and a micrometer is a millionth of a meter.) These are
called respirable or inhalable particles because, as we saw
above, they are small enough to get into the deep lung where they
cause various kinds of damage. The shorthand way to refer to
these pollutants is PM10 (meaning Particulate Matter 10
micrometers or less in diameter). Current U.S. standards say
that the ambient air (the general air we all breathe) may contain
no more than 50 micrograms of PM10 particles per cubic meter of
air as an annual average, and the one-day average should exceed
150 micrograms per cubic meter only one day each year. (A gram is
1/28th of an ounce and a microgram is a millionth of a gram.)
Since 1987, evidence has been accumulating, showing that the 1987
standards do not protect human health. The question about the
existence of a PM10 threshold was addressed first by Joel
Schwartz of U.S. Environmental Protection Agency (EPA). Schwartz
reviewed data on air pollution and deaths from London, 1958-1972,
and showed there was no threshold down to the lowest observed
levels of air pollution. [4] A study published last month in the
NEW ENGLAND JOURNAL OF MEDICINE, of six U.S. cities, including
several that are not heavily polluted, such as Portage, Wisconsin
and Topeka, Kansas, shows death rates increasing with just 15
micrograms per cubic meter of PM10 pollutants. [5] In all, at
least 8 studies have now shown that PM10 at any level kills
people. It seems clear there is no threshold.
A study of people in Steubenville, Ohio, showed that each
increase of 100 micrograms per cubic meter of total suspended
particles (of which PM10 represents about half) is associated
with a 4% increase in the death rate, with no threshold. [6]
Interestingly, the Steubenville study showed that the death rate
changes as fine particle levels change, but not as sulphur
dioxide levels change.
In Philadelphia, a close relationship between PM10 pollutants and
the death rate was observed. [7] Once again sulfur dioxide levels
did not correlate with the death rate, but particle
concentrations did. Here each increase of 100 micrograms per
cubic meter of total suspended particles (of which PM10 makes up
half) was associated with a 7% increase in the death rate. There
was no threshold.
A study of people in Detroit showed that a 6% increase in the
death rate was associated with each increase of 100 micrograms
per cubic meter of total suspended particles (of which PM10 makes
up half). [8] There was no evidence of a threshold. Sulfur
dioxide levels were not significantly associated with increases
in the death rate. Studies [9] of St. Louis, Missouri and
Kingston, Tennessee, showed that the death rate increased 16%
(St. Louis) and 17% (Kingston) with each addition of 100
micrograms per cubic meter of PM10 pollutants to the air.
Associations with gaseous pollutants –sulfur dioxide, nitrogen
oxides and ozone –did not come close to achieving statistical
significance.
In the Utah Valley, a study of the population of Provo revealed
that the daily death rate was closely associated with levels of
PM10 pollution. [10] The Utah Valley is unique because PM10 is
the only pollution present there in significant quantities
(contributed chiefly by a steel mill). For every increase of 100
micrograms per cubic meter of PM10 pollutants, there was a 16%
increase in the death rate, and no threshold was observed.
In all cities, the increase in deaths was most notable among
people older than 65 and in people with chronic obstructive
pulmonary disease (COPD) or cardiovascular disease.
There is a remarkable consistency apparent in all these studies:
a 100 micrograms per cubic meter increase in PM10 is always
accompanied by an 8% to 17% increase in the death rate. Joel
Schwartz, the only EPA employee ever given a “genius award” by
the MacArthur Foundation, re-analyzed data from London’s 1952
killer smog and showed that the death rate increased 6.4% for
each increase of 100 micrograms per cubic meter total suspended
particles, or about 13% for each 100 micrograms per cubic meter
increase in PM10 pollutants–again, remarkably consistent with
the other studies.
No epidemiological study can prove a cause and effect
relationship because it is always possible that some key factor
was not considered. Until last month, skeptics could say smoking
might explain why death rates increase as PM10 concentrations
increase. But the study published last month in the NEW ENGLAND
JOURNAL OF MEDICINE looked at 8111 adults in six American cities
and showed that smoking did not explain the increased death rate
observable when PM10 concentrations rise. [5] Smoking has now
been ruled out.
Joel Schwartz recently quoted the British researcher, Bradford
Hill, saying, “All scientific work is incomplete… All
scientific work is liable to be upset or modified by advancing
knowledge. That does not confer upon us a freedom to ignore the
knowledge we already have, or to postpone the action that it
appears to demand at a given time.” Then Schwartz added: “At
this given time, the knowledge we already have seems to demand a
reduction in population exposure to airborne particles.” [1]
                
                
                
                
    
–Peter Montague, Ph.D.
===============
[1] Seven studies are reviewed by Joel Schwartz, “Particulate Air
Pollution and Daily Mortality: A Synthesis,” PUBLIC HEALTH
REVIEWS 1991/1992 Vol. 19 (1992), pgs. 39-60. For the 8th, see
footnote 5. The 60,000 figure is taken from “Air Pollution in
Typical U.S. Cities Increases Death Risk,” press release dated
May 13, 1991, from the Harvard School of Public Health, Boston,
Mass. describing findings later reported in Joel Schwartz and
Douglas W. Dockery, “Increased Mortality in Philadelphia
Associated With Daily Air Pollution Concentrations,” AMERICAN
REVIEW OF RESPIRATORY DISEASE Vol. 145 (1992), pgs. 600-604. Two
million deaths occur in the U.S. each year; according to Schwartz
and Dockery, fine particles account for 3%. See also, Michael
Weisskopf, “Particles in the Air Help Kill 60,000 a Year, Study
Says,” WASHINGTON POST May 13, 1991, pg. A13.
[2] National Research Council, AIRBORNE PARTICLES (Baltimore:
University Park Press, 1979).
[3] United Nations, FINE PARTICULATE POLLUTION (NY: Pergamon
Press, 1979).
[7] Philadelphia study cited in note 1, above.
Descriptor terms: air pollution; morbidity statistics; mortality
statistics; fine particles; particulates; particulate matter;
fossil fuels; coal; oil; natural gas; automobiles; trucks; soot;
smoke; exhaust; electric power; steubenville; oh; philadelphia;
pa; detroit; mi; st. louis; mo; kingston; tn; provo; ut; utah
valley; pm10; joel schwartz; douglas dockery; bradford hill;
regulations; ambient air standards;