FACT SHEET: Particulate Matter in Indoor/Outdoor Air Does NOT Cause Death

This is the ultimate fact sheet for debunking what has become the U.S. Environmental Protection Agency’s most potent regulatory weapon — the claim that fine particulate matter (soot and dust called PM2.5) in outdoor air kills people. This sheet will be updated regularly as needed. This will be Version 1 (September 22, 2016). Please let me know if you have comments/suggestions.

The Claim. Since 1996, EPA has claimed that PM2.5 causes death.

The EPA’s position is that:

  • ANY inhalation of PM2.5 — even one molecule — can cause death;
  • Death from PM2.5 may occur within hours of inhalation (i.e., on a short-term basis or, literally, “sudden death”) and that;
  • Death from PM2.5 may occur after decades of inhalation (i.e., on a long-term basis).

EPA claims that manmade PM2.5 causes as many as 500,000 deaths annually — i.e., about one in five deaths in the U.S. [1]

In support its claim that PM2.5 kills, EPA points to “thousands” of epidemiologic (statistical studies of human populations), toxicologic (experiments on animals) and clinical (experiments on humans) studies. [2] EPA further claims that the agency’s conclusions have been endorsed by its Clean Air Act Scientific Advisory Committee (CASAC), a board of supposedly “independent” science advisors.[3]

What is PM2.5? PM2.5 (see image below) is very small/fine soot and dust in the air. It has natural sources (e.g., forest fires, volcanoes, pollen, molds) and manmade sources (e.g., smokestack/tailpipe emissions, fires (fireplaces, campfires, grills), smoking). Depending on source, PM2.5 will vary in composition (i.e., PM2.5 in smoke is different than pollen PM2.5).


EPA’s three bodies of research. EPA claims the PM2.5-death hypothesis is supported by existing epidemiology, toxicology and clinical studies. This is false.

  • Epidemiology. EPA admitted in federal court that its epidemiologic studies on PM2.5, because of their exclusively statistical nature, prove nothing by themselves. In 2012 litigation in which EPA attempted to justify its experiments on humans with PM2.5, EPA admitted doing the experiments because: “epidemiologic studies do not generally provide evidence of direct causation.” The purpose of the human experiments, according to EPA, was to develop a medical or biological explanation (i.e., the direct causation) that would support the merely statistical (and, by the way, controversial) results of the PM2.5 epidemiology studies. [4]
  • Toxicology. No laboratory animal has ever died from PM2.5 in an experimental setting — even though animals have been exposed to levels of PM2.5 as much as 100+ times greater than human exposures to PM2.5 in outdoor air. [5]
  • Clinical studies. EPA has tested a variety of air pollutants — including very high exposures to PM2.5 — on over 6,000 human volunteers. Many of these volunteers were elderly or already health-compromised — the very groups EPA claims are most susceptible to dying from PM2.5 exposures. EPA has admitted that there have been no deaths or any dangerous adverse events clearly caused by these PM2.5 exposures. PM2.5 exposures in these experiments have been as high as 21 times greater than allowable by EPA’s own air quality rules.

So EPA’s claim about PM2.5 causing death is not supported by the results from these research disciplines, individually or collectively.

Real-world evidence that PM2.5 does not cause sudden or long-term death. Everyone is constantly and unavoidably exposed to PM2.5 from both natural and manmade sources. Natural sources include dust, pollen, mold, pet dander, forest fires, sea spray and volcanoes. Manmade sources primarily are smoking, fossil fuel burning, industrial processes, wood stoves, fireplaces and indoor cooking. Indoor exposures to PM2.5 can easily exceed outdoor exposures — by as much as a factor of 100. [7]

  • Although EPA claims that almost 25% of annual U.S. deaths are caused by PM2.5, no death has ever been medically attributed to PM2.5.
  • Despite much research, there is no generally accepted medical or biological explanation for how PM2.5 could possibly cause death.
  • Much higher exposures to PM2.5 than exist even in the “worst” outdoor air are not associated with sudden death. The level of PM2.5 in average U.S. outdoor air — air that EPA claims can cause sudden death — is about 10 millionths of a gram (microgram) per cubic meter. In one day, a person breathing such air would inhale about 240 micrograms of PM2.5. In contrast, a cigarette smoker inhales approximately 10,000 to 40,000 micrograms of PM2.5 per cigarette. [8] A marijuana smoker inhales 3.5-4.5 times more PM2.5 — i.e., 35,000 to 180,000 micrograms of PM2.5. [9] Typical water pipe or “hookah” smokers inhale the equivalent PM2.5 of 100 cigarettes per session. [10] There is no example in published medical literature of these various types of short-term smoking causing sudden death despite the very high exposures to PM2.5. [11] Sudden death is also not associated with other high PM2.5 exposures and environments like mines, [12] indoor wood burning, smoking areas [13] or extremely poor quality urban air, for example, in Chinese cities. [14]
  • PM2.5 also doesn’t kill after longer term exposures (i.e., years and decades). The smoking epidemiology proves this. A limited smoker, for example, can inhale more than 4 pounds of PM2.5 from smoking over the course of his lifetime and expect to live as long as a nonsmoker who has only inhaled about two sugar packets worth of PM2.5 from outdoor air. [15]

  • Finally, if EPA really believed that PM2.5 was as deadly as it claims, then the agency would be legally and ethically compelled to stop conducting experiments in which human subjects, including the elderly and health compromised, are made to inhale PM2.5 at rates up to 21 times higher than EPA air pollution standards allow. The agency, however, has refused to cease conducting these experiments. [16]

Transparent science conflicts with EPA’s secret science. The EPA’s claim that PM2.5 causes long-term death is grounded in two long-term epidemiologic studies, commonly referred to as the (1) Harvard Six-Cities Study [17] and the (2) “Pope” study [18]. Both studies are controversial for many methodological reasons. But the methodological controversies cannot be resolved because EPA refuses to release and/or refuses to compel release of the mortality data used in the studies to independent researchers for purposes of re-analysis and replication. For results to be considered to be scientifically credible, they must be capable of being independently replicated. In contrast, a large analysis of the recent daily air quality and daily death data from California for 2007-2010 reports no association between PM2.5 and death. [19] The data from the California study are available upon request from the researchers.

But haven’t EPA’s PM2.5 claims been validated by its independent science advisers? No. The group of independent science advisers formed to review EPA air quality science is the Clean Air Scientific Advisory Committee (CASAC). In 1996, when the CASAC was actually mostly comprised of independent advisers, CASAC concluded that EPA had not shown that PM2.5 caused death. While subsequent CASAC panels have ruled in EPA’s favor, these panels are almost exclusively comprised of researchers who receive hundreds of millions of dollars worth of research grants from EPA — and wind up passing judgment on their own work. These more recent CASAC panels can hardly be considered as independent of EPA. The nature of the PM2.5 science has not changed since 1996 — but composition of EPA’s “independent” panels has. [20]

What about claims that PM2.5 from indoor cooking kill people? The World Health Organization (WHO) claims that smoke from indoor cooking kills more than 4 million people die every year. [21] The studies used to support this claim depend entirely on the EPA’s claim that PM2.5 kills people. So the WHO’s claim is not supportable. While many individual researchers (not EPA-related) have attempted to examine whether indoor cooking increases deaths rates, they have so far not been able to link PM2.5 with death. [22]

Conclusion: PM2.5 does not kill anyone. The EPA’s claims of PM2.5 lethality rank among the most nonsensical, fraudulent and readily disprovable scientific claims ever.


  1. A summary of what EPA claims about the lethality of PM2.5, including links to original documents, is at: http://epahumantesting.com/the-most-toxic-substance-on-earth/. The 500,000 deaths estimate is on p. G-7 of the EPA’s June 2010 “Quantitative Health Risk Assessment for Particulate Matter“.
  2. EPA’s June 2014 “Regulatory Impact Analysis for the Proposed Carbon Pollution Guidelines for Existing Power Plants and Emission Standards for Modified and Reconstructed Power Plants“, page 4-19.
  3. See #2, above.
  4. EPA’s September 2012 “Memorandum In Opposition To Plaintiff’s Motion For Temporary Restraining Order“, page 6.
  5. In 78 Federal Register 3086, 3115 (January 15, 2013), the EPA admitted the only way to kill animals with particulate matter is to first poison them with something else.
  6. See #2, above.
  7. World Health Organization, Household air pollution and health, Fact sheet N°292, Updated February 2016.
  8. See Ghio AJ et al., Particulate Matter in Cigarette Smoke Alters Iron Homeostasis to Produce a Biological Effect, Am J Respir Crit Care Med. 2008 Dec 1;178(11):1130-8. doi: 10.1164/rccm.200802-334OC. Epub 2008 Aug 21.
  9. See e.g., The Effects of Marijuana Smoke, DrugScience.org.
  10. Hookah smoking poses health risks, NIH studies show, NIH Fogarty International Center, March / April 2014 | Volume 13, Issue 2.
  11. Milloy S, What’s EPA Smoking?, Washington Times, November 30, 2012.
  12. Coal Mine Dust Exposures and Associated Health Outcomes
    A Review of Information Published Since 1995
    , NIOSH, April 2011.
  13. See e.g., #10.
  14. Milloy S, China’s bad air puts the lie to EPA scare tactics, Washington Times, January 22, 2013.
  15. How does this photo debunk EPA’s most important ‘scientific’ claim?, JunkScience.com.
  16. See e.g., Milloy S, The EPA’s Secret Whitewash of Illegal Experiments, Washington Times, July 24, 2016.
  17. Dockery D et al., An Association between Air Pollution and Mortality in Six U.S. Cities, N Engl J Med , 329:1753-1759, December 9, 1993.
  18. Pope CA III et al., Particulate air pollution as a predictor of mortality in a prospective study of U.S. adults, Am J Respir Crit Care Med. 1995 Mar;151(3 Pt 1):669-74.
  19. Lopiano KK et al., Air quality and acute deaths in California, 2000-2012, arXiv.org, arXiv:1502.03062.
  20. Milloy S, Corrupting and Independent Science Panel, Washington Times, August 7, 2016.
  21. See #7.
  22. See e.g., Does anyone die from indoor air pollution?, JunkScience.com.

10 thoughts on “FACT SHEET: Particulate Matter in Indoor/Outdoor Air Does NOT Cause Death”

  1. This report/explanation is very welcome, as I’ve often thought “where are the bodies?”, but we not forget the real health problems caused by smoke pollution from indoor combustion of wood, dung & kerosene in 3rd world countries where they don’t have access to clean & reliable grid power (and that includes generation using coal).

  2. While the claims may be widely exaggerated, would you agree that breathing in these small particles is probably best avoided? I remember the awful smogs that were a regular occurrence in the 1950’s in large cities due to smoke from home fires. The clean air act in the UK has definitely reduced these.

  3. Pat Palmer from Prebbleton Christchurch NZ. is a Foundation member of Association for Independent Research. Pat wrote the following piece in the hope it would be published in NZ papers, but has had no luck. His story I believe needs to be told.

    “Twenty years smiting the smog in Christchurch for the good of our health.”

    I came to live in Christchurch 80 years ago. Until Benmore power station was built many years later, the only practical way of keeping warm in winter was by burning coal in open fires. On winter nights the city was smothered in a thick pall of smoke. On bad nights sober people got lost on their way home. We thought of this as “fog”. Most of us accepted it as a necessary nuisance.

    Then in the fifties, people in Western Europe suffered terrible, we thought similar, fogs. Their public health scientists, their epidemiologists, pointed out that these were not fogs, but smog’s. A sort of aerosol of chemical soup from industry and transport, with some from home fires, as in Christchurch. They said that breathing in these poisonous vapours was killing people prematurely. So people in Christchurch began to worry whether our winter air was killing us too.

    In 1966 a panel of eminent scientists convened as the Clean Air Advisory Council reported on what it could find out about it all. They indexed the degree of pollution in the air by measuring its sulphur content, for the main culprit was rightly seen as the coal burned on open fires. The SO2 form this certainly eroded the galvanising off unpainted corrugated iron roofs and fences in Christchurch, so imagine what it could be doing to our lungs!

    The panel could not find any evidence to convince them that our smog’s were harming our health. They compared the respiratory health of people in smoggy Christchurch with the respiratory health of people in well ventilated Wellington. They were surprised to find that the rate of admissions to hospital for respiratory disease was about 50% higher in Wellington than in Christchurch. They surmised that this might be so because Wellingtonians had inherently weaker lungs. But maybe our air was toxic.

    In 1965 Benmore Power station came on stream. People saw abundant, cheap electricity as an alternative for home heating. Electricity had indeed become abundant. Enough to send to Auckland. But cheap, yeah right. Cheap enough to give away to Comalco, but homeowners living under the shadow of the Clyde dam in smoggy Alexandra found that their power was costing them more than it was costing Aucklanders 900 kilometres away. So people still clung to their open fires.

    In the 1970’s came the Kent woodstove. With this and successive “log burners” we could now heat our houses economically with the abundant wood available in Christchurch Coal was no longer the main fuel used for home heating. By 1996 only 5,000 tonnes of coal were burned on home fires in the city. The smoggy nights were becoming a thing of the past. But not fast enough for the clean air fanatics.

    European epidemiologists were saying that the concentration of fine particles in the air with an aerodynamic diameter less than 10 microns (PM10) was a good index of its toxicity. Whether the particles came from burnt toast, or a sausage sizzle or a log burner as in Christchurch, from a blast furnace in Beijing or a petrochemical plant in Pennsylvania, they were all deemed to be equally poisonous.

    So long as they were small enough they were breathed deep into our lungs, where they clogged up the works. Dr Town from the Christchurch Medical School championed this belief, which was eagerly taken up by the “smoky air is poisonous air” lobby, by the Canterbury Regional Council (now ECan) and the Ministry for the Environment. ECan distributed a comic strip of the evil particles lurking in the air to enter our lungs to primary school children. Most of us thought they might be right. But we wondered how right?

    The European and USA epidemiologists developed a formula relating the number of premature deaths, hospital admissions, and Reduced Activity Days which resulted from the concentrations of these fine particles in the air. Measure the concentration of fine particles, use the formula, measure the death toll. So simple! ECan, and then the Ministry for the Environment now began measuring reliably the concentration in the air in Christchurch, and throughout New Zealand.

    Using the European arithmetic, in 1996 Emily Foster (now Emily Wilton) working for ECan calculated that the fine particles in Christchurch air were killing prematurely 20 to 30 people each year. Ten years on, and some 30 to 40 HAPiNZ (Health and Air Pollution in New Zealand) scientists later, sponsored by the Ministry for the Environment and ECan, estimated that PM10 from home fires was causing 140 premature deaths from Chronic Obstructive Pulmonary Disease (COPD) in Christchurch each year. And up towards 2,000 in the whole of New Zealand.

    They listed the percentage of deaths caused by PM10 in localities from Auckland to Invercargill. They estimated that PM10 caused 10% of all deaths in Christchurch each year, but only 3% of deaths in Taranaki. Strangely, they did not compare these estimates with the deaths from COPD recorded as the cause of death in mortality statistics collected and published by the Ministry of Health (MOH). These statistics showed that death rates from COPD varied very little throughout New Zealand. About 6% of deaths were from COPD in both Canterbury and Taranaki.

    Even so, these estimates have been used to justify the introduction of a very low concentration of PM10 as a national standard our New Zealand air must meet. This has resulted in a series of rules and regulations which have banished wood burning from most Christchurch homes.

    How has it all worked out?

    In Christchurch log burners and open fires have been replaced, very expensively, by heat pumps. The concentration of PM10s in the air has almost halved. But is our air any healthier?

    ECan scientists have calculated that there are now 100 fewer COPD deaths here each year as a result. They did not check this conclusion against the MOH mortality statistics. These show that the COPD death rate has not gone down at all as the PM10 concentrations have gone down.

    Then the MfE and the Government Statistician Air Quality Domain Report claimed that death rates and hospital admissions for respiratory disease had gone down as the PM10 concentrations had gone down. They had not gone down. The Asthma Foundation report found that hospital admissions had in fact gone up, not down as claimed in the Government Statistician’s report.

    The MfE gurus and the Government Statistician would have found this out too, had they bothered to look. The Parliamentary Commissioner for the Environment, appointed by Parliament to keep watch on what our officials are saying about our environment, did not ask either.

    From all this I conclude that reducing the concentration of PM10 in the air by banishing log burners has not brought the promised improvements in our respiratory health. It seems that the concentration of PM10s in the air is not a good index of its healthiness. It is useless as a quality standard.

    So what’s being done about it? Never ones to admit defeat, the MfE are proposing to tighten the standards even more. Instead of letting people get on with heating their homes affordably with the waste wood which abounds in Canterbury, ECan is intent on making it even harder and more expensive for people to keep warm. So as the Asthma Foundation report suggests, they may well be increasing winter ills, rather than curing them.

  4. This must be the reason why so many smokers are found dead from no apparent cause with a cigarette dangling from their mouths.

    Big Tobacco has done a terrific job of keeping this from the news!!

    Sarcasm for the win!

  5. Show me the bodies!
    What bull.! Creating fear where none exists.
    If that was true, humans would not have expanded to populate the earth using wood for heat and cooking.

  6. “Yes, you’re paring it down to a form which the general public can understand”

    And I can now understand! Thanks.

    One element left out of any of the “toxic” claims relating to anything, is the body’s self-defense mechanisms.

  7. Congratulations…..
    Yes, you’re paring it down to a form which the general public can understand…when this happens the junk ‘scientists’ will have some unavoidable explaining to do…[unless they can ‘weasel out’ somehow, as they have been doing until now.]

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