One of the challenges health professionals face when forest fires threatentheir communities is to implement effective preventive measures when noguidelines exist for protecting the public in thesesituations.4,10,11
As a result, a goal of this field study was to assess the effectiveness ofinterventions that were rapidly deployed by medical staff of the Hoopa ValleyNational Indian Reservation during an air-quality emergency.
We found mask use to be ineffective and positively associated with outdoorexposure. This finding may be explained by respondent tendencies to use masksinconsistently, without appropriate fit-testing, or by the variable filtrationeffectiveness of the masks used in thissituation.12,13,14
We were also surprised that increased duration of evacuation did not appear tobe protective. However, smoke exposures from wildland fires are oftenunpredictable,15
and among those who evacuated, only 17.1% were away from the reservationduring each of the 3 days with the highest smoke concentrations. In contrast,half of those who used HEPA cleaners ran them during these days, and the meanduration of HEPA cleaner use was twice as long as the mean duration ofevacuation.
The clean air delivery rate (CADR), measured in cubic feet per minute(cfm), is a function of a HEPA cleaner's efficiency of pollutant removal andrate of airexchange.4
TheAmerican National Standards Institute has approved a standard for air cleanersto have a CADR of 100 cfm for a 12- by 12-ft room and a CADR of 250 cfm for a20- by 20-ftroom.16
The HEPAcleaners provided to the population by the Hoopa Valley Tribal Council had aCADR of 150 cfm, suggesting that they would have been suitable for most roomsin the small single-family dwellings on the reservation. Although the use ofportable HEPA air cleaners has previously been reported to reduce theconcentration of fine particles indoors to an acceptable level during smokeepisodes,4
thesefindings provide additional support for their effectiveness because increasedduration of use significantly reduced the odds of reporting worseningrespiratory symptoms.
Economic and occupational barriers to leaving home may have dissuadedreservation residents from evacuating. When asked why they chose not toevacuate to a hotel, 45% of the responses of those who did not evacuateindicated an inability to take time away from work. An additional 12% citedeconomic constraints. In a locale with a 32% unemployment rate, the forestfires brought economic opportunities. This may be best illustrated by thefinding that among working-age adults, residents with preexistingcardiopulmonary conditions were as likely to work for salary in the fire campsduring the fires as others in the community. Future interventions that involvethe temporary relocation of residents may need to consider the positiveeffects of employment (and associated disincentives to evacuation) in order tobe implemented effectively.
Existing research has generally indicated that, to be most effective, therelease of PSAs should be coupled with other behavioralinterventions.17,18,19
A growing body of literature, however, has suggested that PSA campaigns alonecan have significant effects on public healthbehaviors.20,21,22,23
In this situation, the timely dissemination of PSAs through radio broadcastsand telephone messages was associated with a reduction in reported respiratorysymptoms in large segments of the general population. Whereas some evidencesuggests that the PSAs may have produced this effect by influencing recipientsto remain indoors, their mechanism of effect appeared mostly unmeasured by oursurvey instrument and remains an area requiring additional investigation.
In a situation where resources were limited, the interventions wereappropriately prioritized to persons with preexisting cardiopulmonaryconditions, who reported more severe respiratory problems at all time pointsin the study. The effect of each of the four interventions was of similarmagnitude in those who had and those who did not have preexisting conditionsand was also independent of the respondent's participation in any of the otherinterventions. However, a limitation to this study was the potential forrecall bias. To reduce this, respondents were asked to report symptoms foreach of three separate time periods rather than their own change in symptomsover time. Intervention dissemination was also not randomized and wasconfounded by the severity of lower respiratory tract condition. To reduce theeffects of this confounding, several interventions needed to be evaluated byexamining dose-response relations among those who received them.
As population expansion into wildland environments continues, local healthprofessionals will be repeatedly faced with the challenges of making rapiddecisions to protect their communities from forestfires.10,11,24,25,26
Until randomized trials can be undertaken, these findings provide some initialguidance to the effectiveness of several possible community interventions.