The recommendation to ban smoking in cars is made on the basis of research by Aberdeen scientists (as the Evening Express declares proudly), at the Scottish Centre for Indoor Air, which found that:
levels of harmful pollutants were 11 times higher in “smoking” cars when compared with “non-smoking” cars.It seems odd, to say the least, to generalise about smoking cars, as if they all contained equal amounts of smoke, were all of the same size and all subject to the same variable conditions (same number of windows open, vents open to the same degree, and so on).
And although I agree with the Scotsman's leader position on this, their report tells us,
Some experts claim smoking in cars exposes non-smokers to high levels of second-hand smoke which has 23 times more toxins than a busy smoke-filled room. Previous studies have revealed at least three in ten smokers light up in their cars when there are other people present.The same critique can be applied here. There is no standard exposure in a room, which can vary in size, occupancy, air insulation and all other factors pertinent to exposure to contaminants. More significantly this reporting shows no awareness that the British Medical Journal apologised around a year ago for claiming that cars were 23 times more toxic than a bar. They issued an alternative statement: 'the concentration of toxins in a smoke-filled vehicle could be up to 11 times greater [yes, 11 times greater] than that of a smoky bar' (see this link). Quelle coincidence!
The background to the story popping up last year was an announcement of a study carried out by SCIA (link above), which announced the dangers of smoking in cars, where concentrations of toxins were higher than the 'safe level' of outdoor air exposure recommended by the WHO. This is discussed here in some detail (thanks to Michael J. McFadden for assistance), but this part, concerning the relevance of outdoor exposure levels to measuring secondary smoke in cars, is the most damning:
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. [These guidelines outlined in the linked post above]The Scottish Indoor Air Centre's aims are somewhat distressingly focussed on SHS levels, declaring that its priority is:
1. Increasing our understanding of exposure to secondhand smoke in homes and cars (particularly with respect to children’s exposure) and its health effects; exploring possible interventions to reduce exposure in these microenvironments. We believe that the provision of real-time exposure data to smokers is likely to be a very effective mechanism of behavioural modification. [Emphasis added]It is fully involved in the National Lottery-funded project Refresh and ASH Scotland in their bid to encourage smoke-free homes. Hence its emphasis on behavioural change.
The Scotsman is to be applauded for not supporting this move. There is no reason to support it.
I've just come across an account that contains a direct link to the SCIA study (pdf), with some interesting extracts.
Table 2 presents the descriptive statistics of the mean and maximum PM2.5 found during smoking and non-smoking journeys, while Figure 1 shows the time-weighted average (TWA) PM2.5 for each journey, by participant. PM2.5 concentrations in 3 of the non-smoking journeys exceeded the 25 μg/m3 WHO guidance level for indoor air , while this occurred in all smoking journeys for between 11 and 100% of the journey time (53% of the time, on average). [emphasis added]That was one result they didn't shout about. Even with a short car journey the levels of non-smoke contaminants can exceed the EPA 24-hour standard (but this time duration is, according to the standard, is too short to have health implications).
The study also indulges in reinventing the EPA standards:
We have used the WHO PM2.5 guidance level as a comparison as this as the WHO has recently stated that the value can be applied both to indoor and outdoor exposures . The comparison to this guidance should be done with some caution as this health-based value is based on a 24 hour time-weighted average. Clearly the exposures during car journeys we have measured are all much shorter than a 24-h averaging period but given recent work suggesting that there may be no safe level of exposure to SHS  we think that the use of the WHO indoor air standards for PM2.5 is a reasonable health-based method of comparison. [emphasis added]Since the guideline explains carefully (para 28) how to calculate whether the EPA standard is valid for periods shorter than 24 hours this seems to be taking a liberty!
(Read on also about the SCIA's finding about 23, or 11, times as toxic as a smoky bar claim: 'our data do not support this claim nor the BMA's retraction'.)