Finding common ground re PM 2.5’s effect on health, not that simple, it seems

Particulate-matter pollution, a multi-dimensional air contaminant, is of particular concern, especially a finer version of it or that known as PM 2.5 or fine particulate matter less than 2.5 micrometers in diameter (about 1/30^th the width of a typical human hair). That PM 2.5 is present in the air is on account of the incomplete burning of fossil fuels. It can also result from the combining in air of certain chemicals. (See: “Researchers conclude: fertilizer + animal waste + combustion = sooty air” here for much more on this).

The graph below shows various sources of PM 2.5.

As seen, on a grams-per-hour-released basis, the two most notorious sources of fine particulates are diesel truck/bus exhaust and smoke from wood burning in the fireplace.

In the case of the fireplace burning of soft wood, the amount of fine particulates released nears 60 grams per hour. As for diesel truck/bus exhaust from pre-1993 model years, it’s worse: that number is more than 10 grams higher or 70 grams per hour.

Meanwhile, for comparison, gas and oil furnaces produce just a fraction of that: 0.001 and 0.02 grams per hour, respectively.

That’s PM 2.5’s straightforward part. Where this subject gets particularly thorny is over health impacts and whether or not this pollutant is harmful or can lead to premature death. Regarding such, there has been much exhaustive, investigative work, no question.

And the science is clear: What is incontrovertible, indisputable is the accepted notion that the small sooty specks can penetrate lung tissue as well as enter the bloodstream.

Beyond this, the lines are blurred.

In her “‘Unpopular’ science plays a vital role in getting at the truth: Is PM2.5 killing people or not?” commentary, Bakersfield Californian columnist Lois Henry writes: “For anyone who’s followed air pollution science for any length of time, the name ‘[James] Enstrom’ will likely elicit a response.”

According to Henry, an apparently related study was recently published in the journal Dose-Response of which Enstrom is the author.

“What I’ve learned over the years of covering Enstrom and this topic is that while Enstrom’s views may be unpopular, no one has been able to throw shade on his actual work,” Henry confesses.

“In his latest paper, Enstrom uses the American Cancer Society human data – which he won’t say how he obtained (which is bound to be a big deal …) – to recreate [C. Arden] Pope’s 1995 study.

“He shows that you can get a relative risk similar to Pope’s or you can get no relative risk.

“It all depends on which PM2.5 exposure data you use and the best available PM2.5 data yields no relative risk.”

As to being “the best available PM2.5 data”: Henry is able to identify/determine this how?

So I would have to ask: In reading a given number of studies does this automatically make the one doing the reading an expert? Secondly, one needs to take into consideration the context under which commentary is written. Thirdly and lastly there is the matter of being able to interpret all of the corresponding, relevant and pertinent data. If too complex to understand on its own, one certainly has the option of going to the experts for additional explanation, elaboration.

The plot thickens

Now hear (read) this: In the Bakersfield Californian newspaper was this report: “Valley air ranks among the worst nationwide, report says,” by Harold Pierce on April 20, 2017 (incidentally, just five days after the Henry commentary was published). In this article it is written: “Statewide, more than 35 million Californians, or about 90 percent of the state’s residents, live in counties affected by unhealthy air, but Bakersfield experiences more unhealthy days because of short-term particle pollution than anywhere else in the nation, the annual [American Lung Association ‘State of the Air 2017’] report states.”

Of all passages to reference, why I chose this particular one more than any other to cite is because of the word “unhealthy.” Pierce used it twice in one sentence, which, by the way, also is used in connection with the clause “short-term particle pollution.”

Speaks volumes!

Finally, though speaking in general terms, that the “pollution” part as it has to do with air is interchanged with words like “contamination,” “toxin” and “poison,” that this is the case, this is telling.

Graph source: Clean Air Revival, http://burningissues.org/car-www/medical_effects/comp-emmis-part-sources.htm

– Alan Kandel