Benzene - Benchmarks, Standards and Guidelines Established to Protect Public Health

The following is a description of some the benchmarks, standards and guidelines EPA used to evaluate environmental conditions in the aftermath of the World Trade Center disaster.

Benzene is a Volatile Organic Compound, or VOC, found in emissions from burning coal, oil and gasoline and in evaporation at gasoline service stations. These and other sources all contribute to the baseline level of benzene found in outdoor air. Benzene is also released from tobacco smoke.

Benzene levels in urban areas like New York City fluctuate widely, across locations (near idling cars or trucks vs. on the waterfront) and across time (rush hour vs. middle of the night). Routine monitoring involves sampling over a 24-hour period to obtain an average concentration during that day.

Data from routine monitoring sites in New York City collected prior to September 11 find some 24-hour average samples ranging up to approximately 4 parts per billion (ppb). In response to these urban area levels, EPA has adopted several programs to reduce benzene emissions from large urban sources such as motor vehicles. More information on these programs can be found at www.epa.gov/otaq.

Measurements of benzene from World Trade Center smoke and associated cleanup activities (vehicles and equipment) include background levels from other more routine sources such as city traffic. Nearly all of these measurements were "grab" samples, lasting but a few minutes; they are intended to quickly compare levels at the work site with those found in the surrounding streets.

To protect workers at the site, EPA attempted to identify the highest concentration levels of benzene by taking grab samples where smoke plumes have been sighted at the work site. Some of the results were dramatically higher (up to 4000 times) than those taken in the surrounding streets. EPA urged workers to wear respirators and other protective gear, which the Agency and others have provided. Used properly, respirators can protect workers from exposure to benzene and other contaminants at the levels we have found.

Benzene dissipates quickly and grab samples outside the work zone have been drastically lower, indicating dramatic drop-offs in levels as you move away from the debris pile. Full day air samples have also been taken at eight sites, mainly along the outer edge of the work zone. These measurements, which are comparable to levels seen prior to September 11 in New York City, confirm the rapid dissipation of benzene as you move away from the debris pile and illustrate that over a full day, average levels are much lower than many of the levels captured in the few minute grab samples. These full day air samples are all below EPA's screening level which was set to be protective against significantly increased risks of cancer and other adverse health effects. This screening level assumes continuous exposure for a year to an average concentration of 20 ppb.

View Monitoring Data for Benzene in Air