Washington Labor & Industries released a draft emergency wildfire smoke rule on June 15, and discussed the draft during a stakeholders presentation on June 18.
I attended the meeting, and noticed that many of the stakeholder questions concerned evidence on the choice of threshold for PM2.5 in the rule. L&I referred stakeholders to their April presentation, which provided the studies they’ve used to develop the rule.
Most if not all of the studies in the April presentation were not worker-focused, but were studies of PM2.5 exposures and health effects in the general public.
I also noticed that most of the studies were not specifically wildfire smoke studies. One of the only studies they cited that was wildfire smoke related was the UW Doubleday study.
Yet, there are many study wildfire smoke and health effects studies they could have cited as evidence. Two literature reviews on the health effects of wildfire smoke are:
Also, there are more recent studies on wildfire smoke exposure and health effects, including these studies:
The San Diego 2007 wildfires and Medi-Cal emergency department presentations, inpatient hospitalizations, and outpatient visits: An observational study of smoke exposure periods and a bidirectional case-crossover analysis.
The reason why wildfire-specific papers may be useful is that there is some evidence, e.g., in the studies by Rosana Aguilera’s group, that suggests that effects of wildfire smoke may be different from that of non-wildfire PM2.5.
Unfortunately, there isn’t a whole lot of evidence on wildfire smoke exposures for outdoor workers. The exception to this, is that there are quite a few studies for wildland firefighter’s smoke exposures and health effects. Kat Narvarro has a recent paper that summarizes wildfire smoke exposures that different types of firefighters experience. She also describes the evidence for acute impairments in lung function, elevated PAH levels, and elevated systemic inflammation and oxidative stress biomarkers from these studies.
What about occupational exposures to PM2.5 generally? There are a lot of these studies. A quick search of PubMed on “occupational” and “pm2.5” and published since 2016, results in close to 400 papers. Because wildfire smoke is not the same as PM2.5, it’s unclear how relevant these studes are for an occupational rule. Moreover, if an occupational study is on diesel PM, smelter PM, etc., it’s unclear how these specific particle compositions apply to a wildfire smoke specific occupational rule.
Given these uncertainties, and the intent of an “emergency” rule, which is temporary, and meant to provide short-term protection against this year’s potential worker exposures to wildfire smoke, it’s useful to think of The Precautionary Principle:
We’re not sure about workers specifically, but should we do nothing even though there is clear evidence that wildfire smoke is generally associated with acute adverse health effects?
We’re not sure about all outdoor workers, but should we ignore outdoor workers when we find that studies of wildland firefighters who tend to have high exposures to wildfire smoke also tend to show acute adverse health effects?
Finally, in thinking of the potential for harm from a more precautionary approach to worker protection, if part of the solution is providing N95 respirators. This may be a relatively inexpensive solution compared to having worker injuries, having some workers choose not to work to protect their health, or having to stop work completely. The recent paper by Holm, et al., makes some good points about how even though we often talk about fit-testing being necessary to ensure adequate protection under occupational settings, what’s not often discussed is that even a non-fit-tested respirator provides some degree of protection. Isn’t this better than nothing?