From: Andy Soos, ENN
Published June 18, 2012 05:05 PM
Very Fine Particulates
U.S. Environmental Protection Agency (EPA) has just proposed updates
to its national air quality standards for harmful fine particle
pollution, including soot (known as PM2.5). These microscopic particles
can penetrate deep into the lungs and have been potentially linked to a
wide range of serious health effects, including premature death, heart
attacks, and strokes, as well as acute bronchitis and aggravated asthma
among children. A federal court ruling required EPA to update the
standard based on best available science. The current proposal, which
meets that requirement, builds on steps already taken by the EPA to
slash dangerous pollution in communities across the country. Thanks to
these steps, 99 percent of U.S. counties are projected to meet the
proposed standard without any additional action.
Air is filled with very small particulate matter or dust. One can
see it in a ray of sunlight on an otherwise perfectly clear day. It
has many different shapes and many different chemical compositions.
Particulates (sometimes referred to as soot)are tiny subdivisions of
solid matter suspended in a gas or liquid. In contrast, aerosol refers
to particles and/or liquid droplets and the gas together.
The size of the particle is a main determinant of where in the
respiratory tract the particle will come to rest when inhaled. Because
of their small size, particles on the order of ~10 micrometers or less
(PM10) can penetrate the deepest part of the lungs such as the
bronchioles or alveoli. Larger particles are generally filtered in the
nose and throat via cilia and mucus, but particulate matter smaller than
about 10 micrometers, referred to as PM10, can settle in the bronchi and
lungs and cause health problems. Similarly, particles smaller than 2.5
micrometers, PM2.5, tend to penetrate into the gas exchange regions of
the lung, and very small particles (< 100 nanometers) may pass through
the lungs to affect other organs.
A study published in the Journal of the American Medical Association
indicates that PM2.5 leads to high plaque deposits in arteries, causing
vascular inflammation and atherosclerosis — a hardening of the arteries
that reduces elasticity, which can lead to heart attacks and other
cardiovascular problems. Researchers suggest that even short-term
exposure at elevated concentrations could significantly contribute to
heart disease. A study in The Lancet concluded that traffic exhaust
(something fairly hard to avoid) is the single most serious preventable
cause of heart attack in the general public.
EPA’s proposal would strengthen the annual health standard for harmful
fine particle pollution (PM2.5) to a level within a range of 13
micrograms per cubic meter to 12 micrograms per cubic meter. The current
annual standard is 15 micrograms per cubic meter. The proposed changes,
which are consistent with the advice from the agency’s independent
science advisers, are based on an extensive body of scientific evidence
that includes thousands of studies — including many large studies which
show negative health impacts at lower levels than previously understood.
By proposing a range, the agency will collect input from the public as
well as a number of stakeholders, including industry and public health
groups, to help determine the most appropriate final standard to protect
public health. It is important to note that the proposal has zero effect
on the existing daily standard for fine particles or the existing daily
standard for coarse particles (PM10), both of which would remain
unchanged.
Thanks to other recent Clean Air Act rules that EPA has either proposed
or set, EPA has estimated these will dramatically cut pollution, 99
percent of U.S. counties are projected to meet the proposed standards
without undertaking any further actions to reduce emissions.
Depending on the final level of the standard, EPA estimated benefits
will range from $88 million a year, with estimated costs of
implementation as low as $2.9 million, to $5.9 billion in annual
benefits with a cost of $69 million — a return ranging from $30 to $86
for every dollar invested in pollution control. While EPA cannot
consider costs in selecting a standard under the Clean Air Act, those
costs are estimated as part of the careful analysis undertaken for all
significant regulations, as required by Executive Order 13563 issued by
President Obama in January 2011.
EPA will accept public comment for 63 days after the proposed standards
are published in the Federal Register. The agency will hold two public
hearings; one in Sacramento, CA. and one in Philadelphia, PA. Details on
the hearings will be announced shortly. EPA plans to issue the final
standards by December 14, 2012.
For further information see
Soot.
Atmospheric Particulates image via Wikipedia.
©2012. Copyright Environmental News Network To
subscribe or visit go to: http://www.enn.com
|