Even on a Clear Day, PM 2.5 Lurks
April 14, 2011
This essay is in response to: What is the most important achievement we've gained through air pollution management? What remains to be done to safeguard public health from air pollution?
Adults breathe at a resting rate of approximately 12
breaths per minute, thus obtaining 3000 gallons of air per day. Exercise,
stress, pregnancy, and many medical problems will increase the rate and amount.
Babies and kids have a substantially higher rate due to their faster metabolism
and greater activity level. Some people have restricted lung capacity due to
underlying medical problems and must make up by breathing faster. Some, such as
seasoned athletes, singers, and yogis have a more expansive lung capacity and
thus can obtain the necessary oxygen with slower rates. Oxygen is necessary for
us to generate energy molecules from the food we eat and is 21% of the air we
inhale. The brain especially requires oxygen to function normally. That is why
we can’t live without oxygen for more than a few minutes. We have to breathe to
Since we are dependent on air
for our very vitality, it is particularly vexing to me that even 40 years since
the Clean Air Act was legislated, our air continues to be polluted with many unseen
toxic substances that harm that same vitality, especially that of developing
babies and children. It is well known that air pollution contributes to asthma,
exacerbates underlying lung and heart problems and has strong links with
cardiovascular disease and premature death. More recently it has been
associated with diabetes and the development of Alzheimer’s disease. These are
serious and costly medical conditions.
As an OB/GYN, what I find even more alarming is the
emerging research that links air pollution or living near a major roadway to
adverse birth outcomes, respiratory-related infant mortality, and most
Advice on smoking and alcohol cessation, eating healthy, exercising regularly,
avoiding excess weight are all part of a prenatal visit, but how does an
obstetrician counsel pregnant women to avoid something as necessary as air?
Air can be
polluted by a myriad of chemicals. One of the most worrisome is a conglomerate called
particulate matter or PM. Diesel combustion from motor vehicles and stationary sources is a major source of
ambient air pollution including PM,
especially in California. Metallic PM components such as Vanadium and Nickel are
listed as carcinogens by the state of California (Prop 65 list). Like migrating
birds, PM can travel several hundred miles from its origin and can get trapped
in certain regional “cages” due to meteorological and geographical factors. For
instance, PM from San Francisco or Sacramento affects air quality of
California’s central valley, which is some of the worst air quality in the US.
Many magnitudes smaller than human hair, PM is classified
into 3 different sizes: PM 10, PM 2.5, and ultrafine PM.
we often can’t see PM less than 2.5 in our immediate vicinity, we don’t realize it
is there, somewhat like the infamous monkey: see no evil and breathe no evil. But,
believe me, after being absorbed through the tiny air-blood exchange system in
the lungs, PM has the potential to cause much harm to our health through complex
pro-inflammatory pathways and a process called oxidative stress.
Over stimulation of inflammation pathways can lead to autoimmune
disease such as lupus, arthritis, and cardiovascular disease. The body
naturally forms certain levels of reactive oxygen species (ROS) as part of
normal metabolism in mitochondria and to fight off infective invaders by white
blood cells. Too much production of ROS, which occurs with exposure to toxic
pollutants such as PM, can damage our DNA (oxidative stress) leading to damaged
health and loss of vitality. A recent systematic review of the links between air
pollution and adverse birth outcomes reported that exposure to PM 2.5 was
associated with low birth weight, preterm birth and small for gestational age
births (Shah, et al. 2010). Starting off life with this scenario can
lead to a multitude of problems across the lifespan, from learning disabilities
to future metabolic disease and its sequelae.
We obtain anti-oxidants from a rich and varied diet of
fruits and vegetables to keep the naturally occurring ROS in check. However, I
suspect that even if Americans consumed the recommended 5 cups of fruits and
vegetables per day, a significant amount of environmentally induced oxidative
stress would go unchecked. Omega 3 fatty acids are anti-inflammatory, but given
that many fish are tainted with mercury as well as many halogenated and thus
persistent chemicals, it seems counterintuitive to expect that dietary choices
alone can overcome inflammation from exposure to PM 2.5. In other words,
although eating healthy is paramount to our health, we can’t rely on walnuts, eggplants,
Brussels sprouts, and arugula to fight the battle against inflammation and
oxidative stress alone.
Policymakers must take protection of the public’s health
into consideration not only by setting pollution standards that protect our
most vulnerable populations but also by rigorously enforcing the regulations
despite objections of industry. In the instance of PM, this can only be done
after appropriate PM measurement and speciation of PM in the communities most
affected, even if the initial monetary cost seems prohibitive. There would be
billions of health care dollars saved if only a small portion of adverse birth
outcomes were prevented by reductions in exposure to PM and other harmful
Current air quality monitoring does not consistently measure
PM at near roadway sites, the most likely to show the highest levels, but
rather captures regional exposure. The majority of communities are situated
near major transportation arteries and hubs. Many of those are low-income
communities or communities of color, consequently there is no way to really
know the extent or specifics of exposure to PM in these populations. Unfortunately,
these same communities, which are often located in food deserts, also have
reduced access to preventive care, factors influencing health outcomes due to
PM and other air pollution exposures.
The US EPA has issued standards for levels of PM exposure,
which are considered “safe,” and California has even more stringent levels;
however, California has the dubious distinction of having the largest
geographic non-compliance area.
Image courtesy US EPA.
Very soon, the US EPA will be revising the National Ambient Air
Quality standards for PM 2.5 and so a prospect exists to shape and influence future
policy in this regard. I have had the opportunity to work on this project with
an amazing group of women from Central California in a yearlong fellowship
the Decision Makers.” Conceived and managed by the Program on Reproductive
Health and the Environment at UC, San Francisco, the program envisions training
public health professionals to collaborate and become effective advocates for
and communicators of specific policy projects related to reproductive
Our group recently met with US EPA officials in Region IX in
California and at Research Triangle Park, North Carolina, and made the
following policy recommendations:
- Monitors should be placed near roadways that can
speciate the pollutant mixture.
- Such monitors will provide critical data for
future epidemiologic studies that can answer questions about the cumulative
health effects of PM2.5 in communities that live, work, and play
near our roadways.
- These monitors coupled with modeling techniques
will inform appropriate changes that can improve public health of everyone
including our most vulnerable populations.
- The precedent set by the revision of the nitrogen
dioxide rule of the Clean Air Act can serve as a model for PM given they are both
- We recommend that the US EPA estimate the
monetization of adverse birth outcomes to include the lasting effects
throughout life course. These additional costs attributable to air pollution
can then be compared to those of monitoring and reducing air pollution.
Our efforts can be supported by the input of all who value the
fundamental right to air devoid of harmful substances. Please considering
signing on to this petition
or writing to the US EPA when public commentary opens up.
our theme song should be “On a Clear Day You Can Breathe Forever.”