Land Use and Health Risk

Courtesy of the Bloviator is this discussion of the intersection of environmental health risks and land use. He notes that land use planning or city planning is “one of the oldest means through which society can improve public health”, an important element of the Progressive Era that contributed to the foundation of the American Public Health Association.

The impetus for that post is an article published in Occupational and Environmental Medicine that presents an epidemiological study of the association of benzene exposures with occurrence of childhood leukemias (the abstract is published here; a review in WebMD here).

The journal makes non-subscribers cough up $25 for a copy of the paper. However according to the abstract, the paper documents a case control study that analyzed the association between potential environmental exposure to hydrocarbons and the risk of acute childhood leukaemia. A case control study is a retrospective comparison of exposures of persons with a disease (cases) versus persons without the disease (controls), and is one of the more robust study methods in epidemiology (some good resources on epidemiology can be found here and here). The authors concluded there was no clear association was seen between maternal occupational exposure to hydrocarbons during pregnancy and leukemia, or between residential traffic density and leukemia. They concluded there was an association with proximity or residences to gas stations or services garage during childhood and the risk of childhood leukemia, even when corrected for confounding factors. Benzene, a normal constituent in gasoline, is known to be associated with an increased incidence of leukemia.

The potential linkage between outdoor emissions of toxic air pollutants and risks to human health has been a major concern in developing the strategy of air toxics control in the U.S. The U.S. EPA’s National Air Toxics Assessment (NATA), released very quietly in 2002, provides a detailed description of these potential risks. However, what’s always been disquieting to me is that the air toxics strategy never seemed well integrated with studies of indoor air exposure to toxic air pollutants. Nearly 20 years ago, the EPA conducted a large program, the Total Exposure Assessment Methodology (TEAM) study, which showed that personal exposure to volatile organic compounds (such as benzene) was more strongly associated with indoor sources than outdoor ambient emission sources. This conclusion does not appear to have changed over time.

It will be interesting to see how this issue plays out. What is clear is that further studies (air monitoring, modeling, more surveillance) will be needed to make a compelling case that better buffer zones are needed between sources of chemical emissions and residential areas. In the meantime, this becomes a classic precautionary principle/”sound science” debate – how much data are needed before we conclude that there should be changes in how we make land use decisions for industries or facilities that use chemicals.