Washington Labor and Industries Emergency Protection Rule for Wildfire Smoke: Why the Activity Level of Outdoor Workers Puts Them At Risk

The major wildfire smoke episode in September 2020 highlighted the need to protect workers from the potential health effects of breathing poor air quality. While the general public was warned that the level of PM2.5 air pollution was unhealthy, and to avoid exposure, no federal, state or local policies exist in Washington to prevent worker exposures specifically. The concern was especially large for those working in agriculture and construction, or other industries with large numbers of individuals working outdoors.

It also didn’t help from an equity standpoint, that last year’s wildfire smoke episode occured in the midst of the global pandemic: while some people were able to work from home and might be able to shelter indoors to protect themselves from smoke exposure, essential workers in agriculture and construction continued to work outdoors through the smoke.

My group has been following the WA LNI Stakeholder Meetings that have discussed emergency rule-making to protect outdoor workers from wildfire smoke. CalOSHA has adopted a wildfire rule already. Some of the comments heard from the stakeholders call for worker-specific information. And some specifically mention the higher levels of activity of outdoor workers that may put these workers at greater risk.

If we look at the Compendium of Physical Activity, those working in farming or construction occupations might have 4-5 METS (kcal/kg/hour) of activity, compared to a worker who’s sitting, who might have around 1.3 METS.

Differences in activity affects inhalation rates. According to the US EPA’s Exposure Factors Handbook, inhalation rates are about 6 times higher for an typical 30 year adult with moderate activity compared to one in sedentary or passive activity.

If we naively assume all other things being equal, let’s consider the sendentary worker vs the more active Agricultural or Construction worker: over the course of a working day, the Ag/Construction worker will have about 8 hours of work, during which time they’d be inhaling 6 times as much air pollution. Weighted over the 24-hour period, that ends up being 2.7 times higher exposure for the Ag/Construction worker.

Stay tuned. There is more to this than just activity levels and inhalation rates. I’ll write more thoughts in the upcoming weeks.