Determining health risk levels of benzene
by Kathleen McCoy |
Dr. Mary Ellen Gordian, a public health physician and associate professor of environmental health in UAA's Institute of Social and Economic Research, and her research team continue their research on benzene pollution with support of a grant from the federal Environmental Protection Agency given through the Anchorage Department of Health and Human Services. After a successful pilot study of 84 homes two years ago, they recruited 509 households from approximately 1,700 to measure indoor air benzene in their homes and complete health and household surveys. The findings are in a report prepared last month for the Municipality of Anchorage and titled "Health Effects of Indoor-Air Benzene in Anchorage Residences: a Study of Indoor-Air Quality in Houses with Attached Garages." The research is continuing in approximately 70 homes with attached garages in which monthly measurements of benzene are being taken. The study will determine what factors are contributing to the varying levels of fumes inside the houses and how much indoor air pollution varies with seasons. Dr. Gordian and her team expect to acquire additional funding to continue the research: examining the health effects on the people living inside these homes.The original intent of the research was to document the level of asthma in homes where residents may be exposed to very high environmental concentrations of benzene. It was proposed that because benzene affects the immune system people having daily exposure higher than average might be inclined to have greater prevalence of asthma and allergic diseases. Other health effects might also become apparent as the questionnaire asked questions regarding asthma symptoms and self-assessed health status.
To begin the research team had to decide on a level of exposure that might cause health effects. As all exposures were lower than occupational exposures, they looked to the Agency for Toxic Substances and Disease Registry (ATSDR) for guidance. The agency did provide minimal risk levels (MRL) for inhaled benzene that were within the range of the observations. An explanation of the MRL is taken from the ATDRS' Web site.
The conclusions of the completed study are:
The Indoor Air Study measured the indoor air benzene in over 500 residences with attached garages in Anchorage. The level of indoor air benzene exceeded the ATSDR minimal risk levels in almost half of the homes tested. The increased benzene was related strongly to the number of gasoline powered engines including vehicles and small gasoline engines that were in the garage and whether gasoline was stored in the garage. The ATSDR minimal risk levels were determined by extrapolation from studies in humans and animals of much higher exposures and are directed to prevent harm to the most vulnerable members of the population. There was no increase in the prevalence of asthma or allergies in residents living in the homes that exceeded the ATSDR acute level risk. Although there was no increase in prevalence of asthma there was a significant increase in the severity of asthma among the residents exposed to more than 9 ppb of benzene in their homes. People with asthma are a more vulnerable population. This finding supports the ATSDR minimal risk designations for inhaled benzene, indicating that the level of benzene found in some homes in Anchorage is harmful to vulnerable persons.
There is also some suggestion that residents living in homes with levels of benzene that exceed the minimal risk level have a perceived decrease in their state of health. Personal monitoring of this high risk population might help reduce classification errors and inform this important outcome. To read the complete study click here. (http://www.iser.uaa.alaska.edu/Publications/Indoor_Air_Study.pdf)