Background—There is a wealth of evidence showing that particulate air pollution is a cause of adverse cardiovascular effects1 and increased mortality risk.2 3 There is even some evidence that suggests this type of pollution may be a risk factor for diabetes.4 In New Zealand, we have previously conducted studies of fine particulates (PM2.5) from secondhand smoke pollution in hospitality venues5 6 and in cars.7 Pollution from secondhand smoke is a possible explanation for the elevated lung cancer risk in New Zealand bar workers which has been found in a recent study8 (and when adjusted for active smoking). Nevertheless, air pollution from PM2.5 in non-hospitality settings in New Zealand is not well described, and so we performed supplementary pilot study work in settings where vehicle exhaust fumes and cooking fumes were likely to be present.

Methods—Sampled sites in two Wellington suburbs and other details on setting characteristics are shown in Table 1. “Barbecue” restaurants were defined as those that described their food preparation style as “barbecued” in promotional information. Fine particulate levels (PM2.5) were measured with a portable real-time airborne particle monitor, the TSI SidePak AM510 Personal Aerosol Monitor (TSI Inc, St Paul, USA). The methods of our research were similar to that for our published work on secondhand smoke as detailed elsewhere.5 Ethical approval for all this work was obtained through the Category B ethics approval process of the University of Otago and the investigators were cognisant of the ethical issues involved in this type of research.9

Results and Discussion—High levels of fine particulate levels were found in some barbecue restaurants (i.e., means ≥166 µg/m3 for both groups of samples, maximum value of 1472 µg/m3) (Table 1). These high levels are actually not surprising given that they have been found for selected restaurants in other countries10 11 and from home cooking.12 Figure 1 also shows the variation in particulate levels in one barbecue restaurant, with the peaks corresponding to the cooking of food in the dining area. On three separate occasions at this same restaurant, at least one of the two investigators experienced the onset of eye irritation and headaches as the evenings progressed.

Any level of PM2.5 is of some health concern given that the World Health Organization (WHO) states that “no threshold for PM has been identified below which no damage to health is observed”.13 Also, the WHO annual guidelines13 for PM2.5 are set relatively low (at 10 μg/m3) and similarly for the Californian annual standard (at 12 μg/m3).14

High mean levels were also found in takeaway outlets (mean = 159 µg/m3, peaking at 666 µg/m3, Table 1). However, the mean value for all outlets was lowered by two pizza venues which had relatively low mean levels (of <30 µg/m3). A specific concern with pollution in these settings is that the WHO has recently reported that the “emissions from high-temperature frying are probably carcinogenic to humans” (based on human and animal studies).15 In contrast most of the traffic-related settings had relatively low particulate levels, though these were higher in the road tunnel with the walkway (Table 1).

A key limitation with this pilot work is that the air monitor had a calibration factor that was set specifically for measuring fine particulates for secondhand smoke (i.e., 0.3216). Unfortunately ready-to-use calibration factors for vehicle exhaust and cooking fumes have not been published and we did not have the resources to undertake specific calibration studies using gravimetric measures for each different type of pollutant. Similarly, relative humidity levels may also have had some influence on the results but a humidity correction curve for the SidePak has also not yet been developed.17 Therefore these results for restaurants, takeaway food outlets and traffic settings are only indicative measures of a likely air pollution problem in these settings.

Another limitation of this pilot work was that we just measured one hazardous component of air pollution (i.e., PM2.5) and not the many other components such as nitrogen oxides, carbon monoxide/dioxide, ozone, soot and volatile organic compounds. For example, indoor barbecue workers have been found to experience chronic carbon monoxide exposure and associated adverse cardiovascular changes.18 Additional research would ideally consider a wider range of pollutants and even attach portable monitors to consenting workers to capture exposure throughout the working day. Nevertheless, for monitoring progress towards improved air quality, the type of portable air monitor we used may be the most cost-effective approach.

Possible research implications—Given the health hazard posed by particulates and other cooking-related pollutants, we consider that this pilot work should be followed up with larger and more detailed studies. Such research should be funded by health authorities and particularly by occupational health authorities (e.g., Department of Labour). Ultimately such work could inform the case for or against New Zealand adopting indoor air standards for PM2.5 levels (or other pollutants) that would drive improvements in hazard elimination and reduction from a wide range of sources (e.g., cooking fumes and secondhand smoke).

Fortunately, it appears that NIWA are undertaking further research on outdoor air pollution relating to transport in the New Zealand setting.19 Also some early results of New Zealand Transport Agency funded work suggest that the “probable 8-hr occupational guideline of 30ppm for CO [carbon monoxide] is exceeded” in both the Mt Victoria Tunnel and the Terrace Tunnel in Wellington (but particulate levels have not yet been measured in this work).20

While additional air quality research is desirable, such work should not delay progress in more urgent aspects of air pollution control such as making smoking in cars with children illegal as recently recommended by the Māori Affairs Select Committee (given the extremely high particulate levels that can occur in cars—Table 1). Similarly, there are many other reasons (such as reducing greenhouse gas emissions) for strengthening policies that encourage New Zealanders to reduce their car use and adopt non-polluting forms of active transport such as walking and cycling.

* nick.wilson@otago.ac.nz

Acknowledgements: The authors thank colleagues who have assisted with the air sampling work and/or who commented on the manuscript (Richard Edwards, Anthony Maher, Anne Tucker, George Thomson, Margot McLean and Doug Lush). The funding for the SidePak came from the Wellington Medical Research Fund but there was no other funding support for this research.