William M. Briggs

Statistician to the Stars!

Rare Win For Forces Of Sanity: Or, PM2.5 Isn’t As Scary As We’ve Been Told

ransom89

Quick note to a news story in which I have an interest.

WORLD LOGISTICS CENTER: Moreno Valley OKs megawarehouse on 3-2 vote

After three years of controversy that has divided residents, Moreno Valley officials voted Wednesday, Aug. 19 to dramatically transform the city’s east side with what would be one of the largest warehouse complexes in the country.

The council’s 3-2 vote came at the end of three marathon meetings, at which supporters and opponents debated the need for jobs versus traffic and air pollution impacts from thousands of trucks the 2,300-acre project south of the 60 between Redlands Boulevard and Gilman Springs Road will bring…

[Critics] also say that the traffic generated by the project — estimated at 68,721 vehicles a day, including 14,006 trucks — would overwhelm area roads and freeways and increase air pollution and health risks.

A final environmental impact report released in May found that the project would have significant unavoidable regional impacts on traffic, air quality, greenhouse gas emissions, noise and other quality-of-life issues…

[Councilman] Price also asked planning staff to address criticism from state and regional air quality officials that the project environmental study was underestimating the health effects and misusing a single study to claim that diesel particulates don’t cause cancer.

The study to which Price refers, and which he incorrectly says is misused, was the only study I could discover that did not rely on the epidemiologist fallacy to say particular matter (PM) caused disease. The epidemiologist fallacy is when a researcher says “X causes Y” but where he never measures X and where he incorrectly ascribes a causal relation when only a statistical (wee p-value, almost always) one has been found.

The “single” study Price talked about was the (independent) Health Effects Institute’s report “Advanced Collaborative Emissions Study (ACES): Lifetime Cancer and Non-Cancer Assessment in Rats Exposed to New-Technology Diesel Exhaust”. It measured actual exposure of PM to rats using the type of diesel engines that will be used at the World Logistics Center. No wee p-values were discovered.

On the other hand, many wee p-values were found in other observational database “studies” which were the basis of the opposition to the WLC.

I met Benzeevi at the Doctors for Disaster Preparedness meeting in early August where I spoke on the massive over-certainty present in PM-causes-this-and-that studies. Jim Enstrom suggested I should submit a letter to the City Council which was debating the WLC. So I did. Jim put up the entire letter here (at his site).

About one of the studies relied upon by the government agencies, I wrote (SCAQMD = South Coast Air Quality Management District):

The epidemiologist fallacy is present in the SCAQMD-cited 2006 observational study, “Traffic, Susceptibility, and Childhood Asthma” by McConnell and others. In its abstract, this study states, “we examined the relationship of local traffic-related exposure and asthma and wheeze in southern California school children (5–7 years of age).” Yet exposure to traffic was never measured. Instead, the “exposure” children had to traffic was based on a guess (the guess itself was the result of a statistical model, and the uncertainty inherent in the model was ignored). To emphasize, where the children were during the course of this study was never measured, but only approximated. The authors conclude their “results indicate that residence near a major road is associated with asthma.” As noted, it is a statistical mistake to infer, as these authors do, that “associated with” means “caused.”

It might be that living near a roadway causes, in some children, asthma. But are poorer or more well-off children likely to live near a major roadway? Is it the roadway itself that causes the asthma (only in some cases) or it is, say, the poor health or lifestyle of the parents or some other environmental agent? Or is it that more children are being screened for asthma (because of school programs and the like) and that heretofore marginal cases, especially among the poor, went undiagnosed? All these, and many more, unanswered and unanswerable questions are why observational studies cannot be trusted as the sole basis in estimating risk. It is also why observational studies tend to exaggerate risk.

And there are other poor studies, which you can read in the full letter. Jim Enstrom also submitted a letter (here), and so did a Professor Robert F. Phalen (here; I never met him).

This is fantastic news. It shows it is possible to explain how weak is the evidence the old way of doing statistics provided. What’s really needed is a Third Way that avoids all the old mistakes. How about this?

8 Comments

  1. WHAT EVERYBODY KNOWS in Southern California: Smog [reacting with sunlight] leads to ozone, and ozone is dangerous (example: http://www.stateoftheair.org/2013/health-risks/health-risks-ozone.html?referrer=https://www.google.com/ ).

    Numerous studies conducted over decades in numerous countries have established ozone’s harmfulness beyond any doubt.

    EPA’s data shows that S. California’s Inland Empire area (includes Moreno Valley) hasn’t met ozone standards despite truly dramatic reductions in airborne particulate pollution, though ozone levels have decreased (see: http://www.epa.gov/airtrends/ozone.html & earthobservatory.nasa.gov/Features/OzoneWeBreathe/ozone_we_breathe2.php).

    One can be 100 percent certain that an order(s) of magnitude increase in vehicular traffic in an area of the Inland Empire is going to result in some corresponding increase in already too high harmful ozone levels (more on top of too much already is worse; knowing the numbers doesn’t alter the fundamental issue).

    The local region has a number of geographic & weather factors (such as inversion layers & mountains causing air stagnation) that exacerbate the problem; the locals are all intimately familiar with this too.

    That’s physics. Well known & well documented physics.

    Ignoring that, or documenting one’s ignorance (or, perhaps worse, being perceived as a ham-handed hack in bed with a particular special interest) is a risky way to go:

    CONSIDER THIS QUOTE from a letter [intended to be helpful] to the locals: “It might be that living near a roadway causes, in some children, asthma. But are poorer or more well-off children likely to live near a major roadway? Is it the roadway itself that causes the asthma (only in some cases) or it is, say, the poor health or lifestyle of the parents or some other environmental agent?”

    Some in Moreno Valley are clearly willing to accept the health risks & increased traffic congestion for jobs, others aren’t. But nobody there is going to doubt for a second that the order-of-magnitude(s) increase in traffic emissions are somehow not going to include increased health risks. Nobody.

    Quibbling over a single referenced study’s analytical flaws to argue that the case of increased risks of the increased pollution associated with the warehouse aren’t substantiated — to THAT audience – by picking on a particular alleged causal factor (emissions) and effect (asthma) is not going to be compelling to anyone on either side of the warehouse debate…especially when one’s letter documents so very clearly an apparent ignorance of such a basic physical reality so well known locally (“it’s ozone stupid”).

    (a street-wise savvy analyst would’ve noted the obvious while still making their point, saying something like: “Undoubtedly an increase in vehicular traffic & their emissions will, to some extent, undo hard-won local reductions made over the past decade, leading to some degree of increased area smog & ozone levels; however, the cited study is flawed for a number of reasons and as such it is inappropriate to rely on it for making environmental determinations….[then proceed into the ivory tower analysis that next to nobody is going to read; why a particular study was the focus while ignoring the larger reality is a serious omission]”)

    It’s just that sort of “book-smart-but-not-reality-smart” advertising that’s keeping so many prospective employers staying away in droves…so much wasted potential from a philosophical rather than physics/reality-based mindset.

    FOOTNOTE (www.webmd.com/allergies/features/smog-not-an-allergen-but-an-irritant?page=2 ): “Researchers found that during the 1996 Summer Olympics in Atlanta, peak morning traffic decreased by 23% and peak ozone levels also went down, by 28%. What else went down? Emergency room visits for kids with asthma, by a whopping 42%.” Go ahead, say that correlation doesn’t indicate some degree of causality…when we know ozone IS damaging to lung & other tissues…

  2. This is what happens to you if you don’t support the government position.
    http://www.foxnews.com/us/2010/08/31/pc-professors-firing-fueling-exhaustive-debate/

  3. They say a clean air day is LA is “when the mountains come out”, as most of the time they are hidden from view.

  4. “rely on the epidemiologist fallacy to say particular matter (PM) caused disease.”

    particular -> particulate

  5. @Ken,

    PM 2.5 is not smog, nor is it by itself a cause of smog, or of ozone.

  6. Ken has some favorite words that he bandies about. I do not think they mean what he thinks they mean.

    For instance, he says “philosophical.” This is a move I have seen before, from others. He means something like ‘irrelevant’, ‘far-fetched’, or perhaps ‘ridiculous’, but he wants to say that more nicely. He wants to contrast that sort of thing with hard-headed ‘science’.

    To paraphrase Keynes, this does not make him, or people like him, either ‘science-y’, or hard-headed, or practical. It merely makes him, and them, a slave of some defunct philosopher. What a ’cause’ consists of, and whether a p-value can ever speak to that, is irreducibly and perpetually relevant to any science that has ever used or will use statistical comparisons and/or predictions. But Ken, and the many ‘practical’ men like him through the ages, may never actually notice that.

    Another word Ken uses is ‘physics’. In Ken’s hands, somehow it means an absolutely certain and patently obvious stringent causal sequence from a chemical reaction (which, by the way, though relying on physical principles, is, after all, chemistry, not physics) to asthma (medicine) in a particular child (biology, genetics…). Even beside the nicety that none of this is, actually, well, physics — why THIS child and not the child in the house next door? And so forth.

    Matt wrote about the PM 2.5 standard. Ken ignores this and out of the blue brings up ozone. OK, and I don’t know nuttin’ about ozone. But considering what I already had learned about the ‘epidemiologist fallacy’ even before Matt taught us more about it, and the generally non-awesome rigor of conventional studies of air quality and its effects, I’m a tad skeptical. For all I know, ozone in some concentration might even be hormetic.

    You know who Ken makes me almost miss? McJersey Jones.

    Good times.

  7. “You know who Ken makes me almost miss? McJersey Jones.”
    Yes, and I miss David Appell. When you presented evidence that contradicted his claims he would just ignore it and double down.

  8. Crispin in Waterloo

    August 25, 2015 at 11:01 am

    Ken:

    “EPA’s data shows that S. California’s Inland Empire area (includes Moreno Valley) hasn’t met ozone standards despite truly dramatic reductions in airborne particulate pollution, though ozone levels have decreased”

    Ozone is unrelated to PM2.5 in how it is generated. One can find lots of ozone and no PM and vise versa. The study reviewed is about the effects of PM2.5 on health.

    The effects of ozone are well known. The health effects of PM2.5 are little-studied, often modeled, and someone bothered to properly investigate the specific case diesel emissions. Well-done and very relevant. I was surprised that you dismiss the fact that a solid piece of science has been done properly. with a comment implying that doing it once means the results are not important, or they the result is out-weighed by numerous model outputs.

    When looking at the numerous claims made about PM2.5 and health there is a consistent pattern which is to inflate the numbers of DALY’s each 18 months and the number of deaths attributed to this cause. PM2.5 has even been called the most important health risk of all which is an astonishing claim for something not back by measurements.

    Reviewing the most recent ordering of causes of death in a Lancet article last week PM2.5 and IAQ consequences do not appear in list of the top 25 diseases. Perhaps they overlooked it.

    Briggs, your points are well taken. Black carbon nanoparticles will soon make the list of disease agents – be sure of that. With BC however there are not even models, just claims.

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