Environmental Health Tools – TOXMAP

The National Library of Medicine (NLM) announced this month an interactive webmap called TOXMAP, which displays the geographical distribution of toxic chemicals released into the environment in the U.S. TOXMAP is linked to the U.S. Environmental Protection Agency’s Toxic Release Inventory (TRI) as well as the NLM’s TOXNET database. I have found both TOXNET and TRI to be invaluable resources in understanding the occurrence and fate of chemicals in the environment as well as their adverse effects.

Taking TOXMAP out for a spin, I queried it for emissions to the air in 2002 from tetrachloroethylene (synonym: perchloroethylene, or PCE), a chlorinated solvent used for cleaning in manufacturing operations and for dry-cleaning clothes. The queries can be run for a state, city or county in a state, zip code or specific facility (with and ID number you can obtain from EPA’s web site). I ran a query for all PCE emission sources in Ohio, where I reside, which pulled up the 20 facilities in the state reporting PCE emissions (surprising - I guess dry cleaners don’t have to do TRI reporting). The webmap can be centered and scaled appropriately with a few clicks. The emissions sources can be overlain with census tract information, so that you can see population density in relation to emission source strength. Based on the map, you can see an emissions “hotspot” in a relatively densely population area, a few miles southwest of downtown Cleveland. A few more clicks identified that specific facility, and provided its TRI profile. TOXNET can be accessed from the TOXMAP site, for hazard information on PCE.

The NLM press release suggests as an application for this tool, “for example, a family moving to a new city can locate facilities releasing toxic chemicals by entering the city's name and state, generating a map of facilities in that area. For each facility, information, including location and chemicals released, is provided. Information about the health effects of the specific chemicals identified is also provided.” I can also see this being of value to activists, who want to focus on facilities impacting specific communities.

Some of the limitations of the tool are: 1) there is a bit of a learning curve involved. If you are not conversant in chemicals, it could be a bit confusing to use; 2) it can develop maps for only one chemical at a time; and 3) it is important to remember that what TOXMAP is presenting is release information, not information on exposure or potential health hazards.

With air emissions, the magnitude of exposure and locations where significant exposures would occur also take into consideration meteorological conditions and facility characteristics. What would be really cool would be to link TOXMAP with an air dispersion model to provide estimates of potential exposures to chemicals emitted into the air. Maybe that can be for the future – there are a lot of technical challenges to overcome before exposure maps become a reality. For air emissions, EPA has provided something comparable with its National Air Toxics Assessment, which does provide emissions, exposure and health risk information. For example, a NATA exposure map for PCE in air in Ohio looks like this. The associated excess lifetime cancer risk from PCE inhalation exposure looks like this.

The NATA data also has its limitations. For example, with PCE, the predominant source of exposure is indoor exposure from offgassing from freshly dry-cleaned clothes, an emissions source not accounted for either by TOXMAP or NATA. However, these databases make some effort to alert the user to the limitations.

Though the Bush Administration has made significant efforts to limit the public’s right to know about chemical hazards in their communities in the name of homeland security, all hope is not lost yet. There are still substantial environmental health resources available through the internet.