Defense Environment Alert
October 7, 2003

ARMY FACES CHALLENGE WITH LOWERED CHEMICAL AGENT EXPOSURE LIMITS

More stringent airborne exposure limits for chemical nerve agent that the federal government recently set will pose a challenge for the Army at its chemical weapons demilitarization sites, Army sources say. The Army is now assessing the capability of its detection technology in meeting the new requirements, finalized by the Centers for Disease Control and Prevention (CDC) Sept. 17. The standards go into effect Jan. 1, 2005.

The CDC's new airborne exposure limits (AELs) for the nerve agents GB, VX and GA lower worker and general population values by approximately threefold, according to a Sept. 17 Federal Register notice announcing the final recommendations. The new limits will replace levels dating back to 1988. In this case, worker population limits (WPLs) refer to the amount a worker at a chemical demilitarization plant can be exposed to for 8 hours a day, 40 hours a week, over a lifetime without any adverse effects. The general population limit (GPL) refers to protective standards for people in general, including the elderly and the young.

For GB and GA, the CDC lowers AELs for the general population from 3 x 10-1 milligrams per cubic meter (mg/m3) to 1 x 10-1 mg/m3 and decreases AELs for the worker population from 1 x 10-4 mg/m3 to 3x 10-1 mg/m3. For VX, the CDC lowers the GPL limits from 3 x l0-6 mg/m3 to 6 x l0-7 mg/m3, and ratchets down the worker levels from 1 x 10-1 mg/m3 to 1 x 10-6 mg/m3. The new lower values resulted in light of EPA guidance and more data from chemical-related events, says an Army chemical demilitarization operations source.

The CDC decided to give the Army over a year before it has to comply, to allow the service "to implement program changes, regulatory adjustments, and to evaluate quality control issues," the notice says. It will be a number of weeks before the Army will complete an assessment of whether it has the capability to detect to the new limits, the Army operations source says.

A spokesman for the Army chemical demilitarization program says the current WPLs are fully protective. "To go lower is going to be challenging," and will affect the Army's demilitarization activities as well as its storage areas, he says. And this source says there is no better fully-proven technology that can supplant the detection technology the Army now uses. But the Senate earlier this year endorsed an amendment to the fiscal year 2004 defense authorization bill that urges the Army to upgrade its airborne chemical agent monitoring systems at all of its disposal sites, noting that more advanced technologies are on the market. The Army, in response, pledged to initiate a study to immediately determine which technologies will best achieve the objective and to continue improving the monitoring capability (Defense Environment Alert, June 3, p4).

Monitoring alarms at the Army's Tooele, UT, chemical weapons destruction plant currently trigger at 20 percent of the existing requirement, the spokesman says. On occasion, these alarms sound hundreds of times in a day, sometimes in response to benign occurrences, such as pesticide spraying outside the plant or someone's perfume, he says. While this does not always prompt masking of workers and work stoppage, it can if the alarm sounds in an area where workers could be exposed, he says. It takes 45 minutes to 90 minutes to confirm or deny the presence of agent in an area of the plant, he says. This poses a dilemma in which frequent false alarms can lead to people disregarding them, according to the source, who says frequent alarms may have contributed to the "less than stellar safety" culture present at the Army's Tooele plant last year when workers were exposed to chemical agent, causing an eightmonth shutdown. These new CDC numbers are now going to potentially make that dilemma "more acute," he adds.

The CDC also for the first time has issued short-term exposure limit levels to protect workers from adverse effects. These use near-real-time monitors and provide an approach similar to the way the Army already runs its plants, according to the Army operations source. Due to concerns raised by Army contractors and CDC experts about the technical feasibility of meeting the new short-term limits, the CDC adjusted the VX short-term exposure limit (STEL) to 1 x 10-1 mg/m3, a level less stringent than what it had originally proposed. But at the same time, it says excursions to this higher limit should not occur more than once per day, rather than the typical four allowances per day. "[T]he recommended STEL is a result of balancing the detection capabilities and response time," the CDC says. "This adjustment to the VX STEL should not affect worker health," it notes.