Wildland forest fire smoke: health effects and intervention evaluation, Hoopa, California, 1999

Abstract

Objectives: To assess the health effects of exposure to smoke from the fifth largest US wildfire of 1999 and to evaluate whether participation in interventions to reduce smoke exposure prevented adverse lower respiratory tract health effects among residents of the Hoopa Valley National Indian Reservation in northwestern California.

Design: Observational study: epidemiologists from the Centers for Disease Control and Prevention retrospectively reviewed medical records at the local medical center and conducted survey interviews of reservation residents.

Setting: Humboldt County, California.

Participants: Interviews were completed with 289 of 385 residents, representing 26% of the households on the reservation. Of the 289 participants, 92 (31.8%) had preexisting cardiopulmonary conditions.

Results: During the weeks of the forest fire, medical visits for respiratory illnesses increased by 217 visits (from 417 to 634 visits, or by 52%) over the previous year. Survey results indicated that although 181 (62.6%) of 289 participants reported worsening lower respiratory tract symptoms, those with preexisting cardiopulmonary conditions reported more symptoms before, during, and after the smoke episode. An increased duration of the use of high-efficiency particulate air cleaners and the recollection of public service announcements were associated with a reduced odds of reporting adverse health effects of the lower respiratory tract. No protective effects were observed for duration of mask use or evacuation.

Conclusions: Timely actions undertaken by the clinical staff of the local medical center appeared beneficial to the respiratory health of the community. Future programs that reduce economic barriers to evacuation during smoke episodes may also improve intervention participation rates and decrease smoke exposures. Although promising, the effectiveness of these and other interventions need to be confirmed in a prospective community intervention trial.

Figure 1

Average weekly ambient concentrations of particulate matter(PM₁₀) (horizontal lines) and number of medically attendedrespiratory visits (ICD-9 codes 460-519) (vertical bars) among residents ofthe Hoopa Valley National Indian Reservation, by week, August 17 to November4, 1998 and 1998. The bivariate correlation coefficient for 1998 was r = -0.63and for 1999 was r = 0.74.