Today we review research into the occurrence of brief peaks of suspended particles (or dust), how often they occur (in a rural area of southern Ontario) and if the results point to a need for standards for periods of less than an hour- the shortest time period currently used in Canada and many other countries. The resulting analysis showed that peak values of PM10 twenty to one hundred times greater than values averaged over an hour which were within the current standards. Although the aim of the research was to examine single events with high associated levels of pollution, one cannot help but wonder what the health impacts would be for people exposed to repeated doses of high pollution for shorter periods than are covered by existing standards, such as proximity to roadside emissions at rush hour each day. If there is a definable health impact, that would both call for standards for shorter periods- say 10 minutes or one minute- and might explain the degree of mortality associated with traffic (which has been estimated as about 1/3 of all deaths from outdoor air pollution in a study conducted by the City of Toronto Medical Officer of Health).
Key Quotes:
“In occupational settings, brief and even singular exposures to high levels of irritant dust, vapour, fume or smoke has, in patients with no prior history of respiratory disease, been described as the causative agent in reactive airways dysfunction syndrome and irritant-induced asthma, resulting in symptoms of airway inflammation and bronchial reactivity without a latency period”
“Canadian standards identify 1-hour mean limits for sulphur dioxide, ozone, nitrogen dioxide, and hydrogen sulphide, but do not place limits on relatively brief peak allowances for PM2.5 or PM10 by defining limits at the 98th percentile or through 24-hour and annual means”
“We analysed these data from a public health perspective in order to determine if local air quality complaints could be traced to elevated particulate levels.”
“Our novel methodology revealed extreme outlier events above the 99th percentile of readings, with peak PM10 and TSP levels over 20 and 100 times higher than the respective mean values.”
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