Parallels between community environmental health and occupational health.

Abstract

Since September 11, 2001, there has been increased attention on whatindividuals and communities can do to minimize the effects of terroristattacks, and other disasters, on the health and safety of our family, friends,and community.1 Thearticle by Mott and colleagues focuses on one such disaster—a forestfire. It provides retrospective data that can give us some idea about whichinterventions work and which do not in preventing respiratory healthproblems. Unlike most disaster situations, the forest fire that occurred from Augustto November 1999 near the Hoopa Valley National Indian Reservation in northernCalifornia caused a gradual buildup of smoke concentration in the residentialarea of the reservation. This gradual buildup provided an opportunity forlocal health officials to implement health-protective measures. The results ofa follow-up study, reported here, provide some guidance for health planning infire-prone areas and more generally for response to other natural andhuman-made disasters. Over the 7-week period of the fire, smoke particulate concentration(PM10) exceeded 150 μg/m3 for 15 days and reached apeak of more than 500 μg/m3 for 3 days. The EPA has designatedthe health-based national air quality standard for PM10 as no morethan 150 μg/m3 (measured as a dailyconcentration).2Hence, the PM10 in the study area reached hazardous levels. Toreduce the health effects of the smoke exposure on susceptible members of thecommunity, local health officials implemented four types of interventions:distributing respiratory protective masks, providing free vouchers to stay athotels in nearby towns, providing portable HEPA filter units to residences,and releasing PSAs. After the fire, a study was conducted to determine thehealth effects of the fire and the effectiveness of the interventions. The situation faced by these health officials is analogous to thatfrequently encountered in the field of industrial hygiene, so it is ofinterest to compare the approaches taken by community health officials withthose used to address chemical exposures in industrial settings. The basicindustrial hygiene paradigm includes three steps: recognition, evaluation, andcontrol.3 The firststep is to identify the contaminant. In the case of the forest fire, it wasidentified as smoke particulate, although irritating gases in thesmoke—such as aldehydes—could also have been present. Theevaluation step is a quantitative measurement of the environment and anassessment of the health risk it presents. This was done in Mott andcolleagues' study by comparing air-monitoring data with EPA standards. Thethird step, to control the exposure to safe levels, was undertaken by the fourinterventions mentioned above. In industrial hygiene, control methods are ranked hierarchically byefficacy andreliability.4 Thebest methods are engineering controls, such as substituting safer materials,isolating workers from the exposure, and ventilation. The analogy for thiscategory would include evacuation and the use of HEPA filter units. Furtherdown the list is modification of work practices, which include training in thenature of the hazard and what exposed persons can do to minimize theirexposure. This is analogous to the PSAs that were disseminated. Finally, theleast effective is personal protective equipment, in this case, respirators.Respirators are the least effective because it is difficult to get a good fit,they cannot be used effectively while eating or sleeping, and they causeconsiderable discomfort when worn for long periods. In this study, how successful were the different interventions? Before wecan answer this question, we need to be cautious in interpreting the databecause they are observational and retrospective, so they are prone toconfounding and bias. The data show associations between an intervention andan outcome, but there is no proof that the intervention caused the outcome.With this caveat in mind, the data do seem consistent with the industrialhygiene control hierarchy in that the use of HEPA air cleaners and therecollection of PSAs were both associated with reduced odds of reportingadverse respiratory effects. The possible protective effects of PSAs suggestthat people are prepared to take steps to protect their health if they areinformed of the risk and the steps to be taken to minimize that risk. In the industrial hygiene control hierarchy, we would expect evacuations tobe effective. Yet, evacuation in this case did not appear to be protective. Itis unclear why. Particulate concentrations in the nearby communities are notreported in the study, and perhaps these were elevated. Also, only a few ofthe participants were evacuated for the entire period of highestconcentration. The study provides useful information for health planning in areas prone toforest fire. It also serves as a model for planning public health response toother types of natural and human-caused disasters. It underscores the need tokeep good records of the implementation of interventions for lateranalysis.