Is Air Pollution Killing South Africans?
Jacobus Erasmus, 19 June 2019
A study has been circulating on the news in South Africa that air
pollution is dangerous for our health. For example, the Vaal
Weekblad has an article titled
pollution by Eskom and Sasol is killing South Africans – Study”.
What a scary title!
study being circulated is from Andrew
Gray, an American air pollution consultant. In the paper,
Gray states that “Ambient PM2.5 pollution from the 14 facilities
[in the Highveld] caused between 305 and 650 early deaths in the area
in 2016.” The term “PM2.5” or “fine particulate matter”
refers to tiny particles in the air that have a width smaller than
2.5 microns. These tiny particles can originate, for example, from
vehicle exhausts, power plants, and burning wood or coal. Thus,
according to Gray, the Eskom power plants are producing levels of
PM2.5 that can and are killing people. Again, what a scary claim!
is this claim true? How, exactly, does Gray know that the air
pollution is causing these deaths? An examination of Gray’s
methodology on pages 21-23 reveals that his methodology is flawed.
Gray uses a mathematical model (based on Burnett’s
et. al. model) to predict
or estimate the
health problems that may be attributed to certain exposure to PM2.5.
Setting aside the issue as to
how reliable the model is, it is fallacious to argue that, if
something has been estimated, then it will or has been actualised.
argument has the following form:
(1) The Highveld air pollution might have caused X number of deaths.
(2) Therefore, the Highveld air pollution did cause X number of deaths.
(2) does not follow from (1); Gray’s conclusion does not follow
from his estimate. This would be similar to me arguing as follows:
(1) I predict that South Africa will win the cricket world cup.
(2) Therefore, South Africa will win the cricket world cup.
(1) I might win the national lotto.
(2) Therefore, I will win the national lotto.
reasoning is fallacious. Accordingly, the most that Gray could have
concluded from his study is that ambient PM2.5 pollution from the 14
facilities in the Highveld might have caused between
305 and 650 early deaths in the area in 2016.
Gray’s methodology cannot rule out the possibility that
non-pollution factors are the primary causes of the deaths. How do we
know for certain that, for example, those who died did not get ill
from smoking, or inherent heart issues, or some other health issues
unrelated to air pollution? Gray’s predictive model or methodology
simply cannot tell us that air pollution did,
in fact, cause the deaths. Indeed,
Gray succumbs to a well known problem in observational studies about
air pollution: such studies are almost completely circumstantial. As
Joel Schwarts, an expert in air pollution, says:
An embarrassment for proponents of low-level air pollution as a cause
of death is that the evidence is almost solely circumstantial, being
based on statistical studies reporting small correlations between
long- or short-term air pollution levels and risk of dying. These
“observational” studies are not based on randomized trials, but
on non-random data that inherently suffer from confounding by
non-pollution factors with much larger effects on health than the
purported effects of air pollution. Observational studies could be
taken more seriously if they were supported by evidence from
randomized, controlled studies that eliminate the possibility of
con-founding by non-pollution factors. Such studies cannot, of
course, be done with people, but they can be done with animals.
However, researchers have been unable to kill animals with air
pollution at levels anywhere near as low as the levels found in
ambient air (Air
Pollution and Health
, 2006, p. 5).
Gray’s estimates, in reality, do not tell us very much.
Gray’s study assumes the following proposition:
(P) The inhalation of PM2.5 produced from air pollution might cause
assumption has been used by many to claim that air pollution in the
U.S. causes thousands of premature deaths to occur yearly. Now, Gray
does not show that (P) is true but he simply assumes it to be true.
However, current research renders (P) implausible. For example, in
his article Scientific
Distortions in Fine Particulate Matter Epidemiology, Dr James E. Enstrom explains:
The theoretical prevention of premature deaths from the inhalation of
fine particulate matter is being used by the U.S. Environmental
Protection Agency (EPA) to justify the National Ambient Air Quality
Standard (NAAQS) and multibillion dollar regulations across the U.S.,
including the EPA Clean Power Plan and the California Air Resources
Board (CARB) Truck and Bus Regulation. The epidemiology is severely
flawed. Fine particulates probably make no significant contribution
to premature mortality in the U.S. The publication of null findings
has been blocked or marginalized and studies claiming excess
mortality need to be reassessed.
Similarly, in their research paper titled Air
quality and acute deaths in California, 2000-2012, Young et.
Many studies have shown an association between air quality and acute
deaths, and such associations are widely interpreted as causal.
Several factors call causation and even association into question,
for example multiple testing and multiple modeling, publication bias
and confirmation bias. Many published studies are difficult or
impossible to reproduce because of lack of access to confidential
data sources. Here we make publically available a dataset containing
daily air quality levels, PM2.5 and ozone, daily
temperature levels, minimum and maximum and daily maximum relative
humidity levels for the eight most populous California air basins,
thirteen years, >2M deaths, over 37,000 exposure days. The data
are analyzed using standard time series analysis, and a sensitivity
analysis is computed varying model parameters, locations and years.
Our analysis finds little evidence for association between air
quality and acute deaths. These results are consistent with those for
the widely cited NMMAPS dataset when the latter are restricted to
California. The daily death variability was mostly explained by time
of year or weather variables; Neither PM2.5 nor ozone
added appreciably to the prediction of daily deaths. These results
call into question the widespread belief that association between air
quality and acute deaths is causal/near-universal.
Steven Hayward says,
Air pollution affects far
fewer people, far less often, and with far less severity than is
commonly believed. ...
The air pollution-mortality claim deserves even greater skepticism.
First, is is based on the same unreliable correlation moderns that
have led medical authorities astray in other areas. Second, even
though pollution was correlated with higher premature mortality on
average, it seemed to protect
against death in about one-third of cities. How could pollution kill
people in some cities and save them in others? More likely, both
results are chance correlations rather than real effects. Third,
researchers have been unable to kill animals in laboratory
experiments, even when they expose them to air pollution at levels
many times greater than ever occur in the United States. This
suggests that air pollution at today’s record-low levels doesn’t
pose a risk, and current standards are health-protective with plenty
of room to spare.
Warren Kindzierski, associate professor in The School of Public
Health at the University of Alberta, calculates
that "any epidemiology
study claiming air pollution causes a disease will have a less than
18 per cent probability being true at a prevalence rate of 0.1". He continues:
When it comes to sharing results of
these studies with the public, epidemiologists and too many reporters
ignore another truth. They make bold claims that air pollution may
cause a disease, but these claims are unlikely true. They seldom
offer results about air pollution not causing a disease, even though
these results are very likely true. This is a form of reporting bias
(only offering selective results or suppressing results) that people
should be aware of. Really, the true headline of air
pollution-epidemiology studies is… Claims that present-day air
pollution may cause [enter disease name here] are mostly false!
these reasons, Gray’s claim that the Highveld air pollution did,
in fact, cause the deaths of around 600 people in 2016 is
irresponsible and cannot be taken seriously.
what about the less severe health danger of asthma? Can air pollution
cause asthma? Once again, we simply do not have enough reliable
evidence to think that air pollution necessarily causes asthma. In their 2002
in exercising children exposed to ozone: a cohort study,
McConnell et. al. found that,
in general, there is no
greater risk of developing asthma for children in high polluted areas
than in low polluted areas. In fact, when considering all the
children in the study, the children in the high polluted areas were
about 30% less likely
to develop asthma:
Risk of developing asthma was not greater overall in children living
in the six high pollution communities than children living in the six
low pollution communities, after adjustment for stratified baseline
hazards for age and sex, and for ethnic origin, irrespective of which
pollutant was used to classify communities as high or low. ...
Communities with high NO2 and associated pollutants, and communities
with high ozone or daily maximum ozone were associated with a
decreased risk of asthma; these associations were significant ...
only for daily maximum ozone (p. 388).
claims that air pollution cause asthma are often exaggerated.
course, this does not mean that air pollution does not have negative
side affects. It is plausible that air pollution might have some
negative short-term health affects, such as negative respiratory
symptoms or blocked nose, but these are scarce and usually not
2003, p. 27). But the above facts do show that the dangers of air
pollution are often exaggerated. What is the reason for this
exaggeration in the media? Joel Schwartz offers a plausible answer:
Studies that report harm from air pollution are more likely to be
published than studies that do not. Regulatory agencies, whose power
and budgets depend on the perception that air pollution is a serious
health problem, are also major funders of the research intended to
demonstrate the severity of the problem. Scientists who believe air
pollution is a serious health threat and who report larger health
effects are more likely to attract research funding. It is not a big
leap to conclude that there is a great deal of selection bias in who
does environmental health research, what questions they ask, and how
they report their results. Journalists should be acting as a check on
air pollution misinformation, but they are not. Media outlets face
their own pressures to sensationalize stories. Good news does not
sell newspapers or attract viewers. As a result, journalists and
editors are more likely to cover studies claiming harm from air
pollution, and to pass along these claims with little or no critical
Pollution and Health
, 2006, p. 8).