Smoking in cars declared out of order by Greater Glasgow Health Board

Last week, many articles in the Scottish news media warned the public off smoking in cars, because the dangers to children were said to be phenomenally high: concentrates were higher, we were told, than in Scottish pubs before the ban. Don't bother opening your window, we were also told, because it won't make any difference (or enough difference).

Mr Gray in Glasgow is persuaded.

... I am certain most of the public will feel the same and condemn those who continue to puff away when they have kids in the car.

The law should be changed to deal with this, as serously as being caught, say, using a mobile phone while driving.

The Executive Summary of the NHSGGC report that kicked this off leaves much unanswered. The report shows an alarming picture of particulates in a smoky car at 14 times what they are in a car where no smoking was taking place, and peak concentrates at shocking levels:

The arithmetic mean PM2.5 concentration during journeys where smoking took place was 95 µg/m³, approximately 14 times higher than the mean figure of 6.8 µg/m³ measured during non-smoking journeys. Peak levels across the 26 smoking journeys averaged 410 µg/m³ compared to 12 µg/m³during nonsmoking journeys. The highest peak PM2.5 concentration of 886 µg/m³ occurred during a smoking journey.

At no point in any of the non-smoking journeys did PM2.5 concentrations exceed the 35 µg/m³ US EPA outdoor air guidance concentration for unhealthy air. All smoking journeys exceeded this threshold at some stage of the journey with the percentage of the time when concentrations rose above 35 µg/m³ ranging from16 to 100% (mean 49%).

Here's a useful analysis:

As a preface it is important to note just what [the Scottish Centre for Indoor Air] has chosen to measure and report on in compiling the report, something called “FPM 2.5.”  FPM 2.5 is the designation given to any particulate matter in the air that is 2.5 micrometers (microns) in diameter or smaller.  Normal people call it smoke or smog.  If you allow smoking in a place most people will realize that you will probably have smoke (FPM 2.5) in that place. If you go outside on particularly smoggy day you’ll be able to see FPM 2.5 in the outdoor air as well.

But there’s something very fundamental and important to remember when speaking of FPM 2.5: it is simply a measurement of a certain size range of particles.  It says nothing about what those particles consist of or how dangerous they are.  To pretend that the particles produced by the quiet burning of a few leaves in a scrap of paper is the same as the particles produced by the high temperatures and/or pressures of internal combustion engines, industrial processes, commercial incinerators, or even a roaring fireplace is simply false.  It’s like pretending that a teaspoon of sugar crystals is just as deadly as a teaspoon of arsenic crystals simply because both happen to have crystals of the same size.

And yet it is this false premise that lies at the very base of the SCIA Report.  Are the FPM 2.5 levels produced by cigarette smoke dangerous in the same way as the chemical air pollution produced in the air of our cities?  It could be argued that it is possible but it certainly can not be argued that it is known. It could very well be that it is indeed like comparing arsenic crystals and sugar crystals, and it could also be that just as concentrated amounts of sugar can be unhealthy for certain small populations (e.g. diabetics) that concentrated amounts of FPM 2.5 from tobacco smoke could be unhealthy for certain small and sensitive populations (e.g. those with impaired breathing, those with severe cardiovascular disease, those who are very old or very young.) 

Note however the importance of the word “concentrated.”  If two chain smokers are driving for hours in a car with such a  sensitive person and keep the windows rolled up tightly all during their trip, then yes, it could well be rationally argued that a real problem might exist.  To argue that the same problem exists when moderate smokers roll a window or two down a few inches while driving at normal speeds and smoking is something else entirely: the all-important “air changes per hour” that ventilation engineers concern themselves with is probably about 2 or 3 with the windows closed tightly, but more like 200 or 300 when the windows are opened.  To equate the two situations is simply a lie.

And there is more:

In addition to the above problems the SCIA report seems to deliberately make another very fundamental error, one that it would be difficult for the authors to plead innocent of.  While it is true that according to agencies such as the US EPA that urban, automotive, and industrial air pollution has been shown to be unhealthy or even dangerous when it reaches higher levels for periods of 24 hours or more, it is also true that the EPA doesn’t set standards for FPM 2.5 for shorter periods because there is no sound medical reason to believe that shorter episodes of such exposures actually pose a threat to health.  When the SCIA takes readings during car journeys that typically last less than several hours and tries to apply the EPA’s 24 hour standards to those readings, it is explicitly violating the very guidelines of the EPA itself.

Explicitly?  Deliberately?  Am I being unfair?  I don’t think so.  Here is the relevant passage from page 42 of the EPA’s own GUIDELINE ON DATA HANDLING CONVENTIONS FOR THE PM NAAQS for the use of its calculations:

If measurements are available for less than 75 percent (17 or less) of the hours during the 24-hour period, you must treat the 24-hour average as invalid, unless the concentrations are too high to be ignored, as determined by the following calculation:

A. Compute the lower bound. Substitute zero for each missing hour and compute the average over all 24 hours.

B. Round the lower bound. Round the lower bound to the nearest 1 µg/m³ for PM concentrations (round up decimals 0.5 or greater). Round the lower 2.5 bound to the nearest 10 µg/m³ for PM concentrations (round up integers 10 of 5 or greater).

C. Compare the rounded lower bound to the standard. If the rounded lower bound exceeds the level of the 24-hour standard, use the unrounded lower bound as the valid 24-hour average. Otherwise, treat the 24-hour average as invalid. 

Michael J. McFadden

What measurements do we have to go on? 

• the EPA safe level for healthy air is given as 35 µg/m³
• peak levels of particulates in the non-smoking car were about 12 µg/m³
• peak concentrations in the smoking car averaged 410 µg/m³ in the smoking journeys (while what they call the mean average was about 95 µg/m³).

The report (so far we only have access to the summary) doesn't define the lower bound but surely in a range with peak average of 410 µg/m³, an absolute maximum of 886 and an overall average of 95 µg/m³, the lower end of the range must have been very very low. Nor does it tell us how long the journeys were, but it's hard to see why journeys of this experimental nature should exceed two or three hours. We do know however from the Executive Summary that for up to 15 per cent of the smoking journeys the meter read <35 µg/m³, and it therefore seems clear that the pollution described in this report is insignificant in the terms defined by the Environmental Protection Agency (who set the 35 µg/m³ safe level), indeed that the SCIA has violated the EPA standard by its use of the figures.

So ... in the first place, we don't even know for sure that the particulates from smoke do any damage, just because of their size. In the second place, since the EPA levels are designed to apply to prolonged exposure, the pollution levels actually fall comfortably within the safe ranges defined.

In the Evening Times article, further misconceptions come to light. For example:

Dr Sean Semple, of the Scottish Centre For Indoor Air, was part of the research team. He said: “The air quality during smoking car journeys is much worse than normal outdoor air pollution levels.” 

This seems to miss most basic toxicity lessons. A car journey is often quite short, and even when it is long, smoking might occupy a very short part of it. Outdoor air pollution in busy cities will vary with the time of day and the weather but in general is much more constant than what you will find in a car. (Even in the non-smoking car, particulates didn't measure zero.) Furthermore particulates are only part of the story of outdoor air pollution – particulate measurements won't pick up noxious gases. 

MJM concludes:

The final paragraph of the Summary consists of three sentences, each of which is important enough to be examined on its own:

1)    PM2.5 concentrations in cars where smoking takes place are high and greatly exceed levels that are deemed to be unhealthy in outdoor air.

 The above statement was dealt with in the opening paragraphs of this Critique.  The comparison with EPA type 24 hour standards violates the very conditions of the guide and as such it should never have been permitted in such an official document as this Summary.  Not only are the FPM 2.5 measurements measuring something chemically and probably clinically quite different from the EPA measurements setting “unhealthy” level guidelines, but the EPA itself forbids usage of its guidelines while disregarding the 24 hour exposures for which they were set.

2)    Smoking in cars leads to exposure to SHS that is likely to be damaging to health. 

This statement is not in any sense supported by the data in the Report.  The Report does not show any data, at least not as indicated in its Summary, that would support such a claim for brief exposures at the levels measured.  This statement should also be stricken from the Summary.

3)   Measures to restrict the exposure of children to SHS should be considered at both an individual and a societal level.

This final statement is reasonable, but it should be more open about what it is urging: it is calling for the government to enact legal measures and remedies to “restrict the exposure of children” to SHS by their parents, not just in public places, but in the confines of vehicles and private homes.  It would have been a more honest concluding statement if it had said:

 “Measures to enact laws to restrict smoking in private homes and vehicles where minors are present should be considered even if the minors in question are themselves smokers.  Such measures obviously will also require the consideration of proper penalties and the removal of such children in the face of persistent parental smoking. Since the eyes of the government cannot be in every home, children should be empowered and encouraged to report on their parents if such exposure occurs with the parents being duly dealt with through fines and imprisonment.”

ASH Scotland has not yet nailed its colours to the mast and demanded a smoking ban in cars.