Risk factors associated with clinic visits during the 1999 forest fires near the Hoopa Valley Indian Reservation, California, USA

Abstract

Forest fires burned near the Hoopa Valley Indian Reservation in northern California from late August until early November in 1999. The fires generated particulate matter reaching hazardous levels. We assessed the relationship between patients seeking care for six health conditions and PM₁₀ exposure levels during the 1999 fires and during the corresponding period in 1998 when there were no fires. Multivariate logistic regression analysis indicated that daily PM₁₀ levels in 1999 were significant predictors for patients seeking care for asthma, coronary artery disease and headache after controlling for potential risk factors. Stratified multivariate logistic regression models indicated that daily PM₁₀ levels in 1999 were significant predictors for patients seeking care for circulatory illness among residents of nearby communities and new patients, and for respiratory illness among residents of Hoopa and those of nearby communities.

Keywords:

• asthma
• confounding variable
• wildfires
• Hoopa valley
• interaction
• logistic regression
• PM₁₀ levels
• respiratory illness

Acknowledgements

The authors would like to thank the reviewers whose comments greatly improved the presentation of this paper. In addition, special thanks are given to Eva M. Smith and Emmett Chase of the K'imaw Medical Center, without whose help this investigation would not have been possible, Anna Blake for assistance with the K'imaw Medical Center data, and Robert Uliharri and Lucky Guyer of the Hoopa Environmental Protection Agency for their assistance with the air quality data.

Additional information

Notes on contributors

Kenneth Falter

Retired