Defense Environment Alert 05/18/04

Defense Environment Alert

an exclusive biweekly report on defense policies for cleanup, compliance and pollution prevention

Vol. 12, No. 10--May 18, 2004

CDC ISSUES NEW AIRBORNE EXPOSURE LEVELS FOR MUSTARD AGENT

The Centers for Disease Control & Prevention (CDC) has issued new airborne exposure limits for mustard agent, backing levels less stringent than the standards it proposed last July. The new levels will nonetheless require the Army to put in place additional agent monitoring stations and conduct more frequent analyses of mustard agent at lower levels than it does now, an Army source says.

The source says the Army, which asked for the CDC review, will not have any problems meeting the new levels, however. The levels apply to the Army's chemical weapons destruction plants, several of which are destroying mustard agent.

The CDC is allowing the Army until July 1, 2005, to implement its interim recommendations for airborne exposure limits (AELS) for chemical warfare agents H and HD, commonly referred to as mustard agent. The year-plus implementation period will allow the Defense Department to make program changes and request modifications to environmental permits, the CDC says in a May 3 Federal Register notice.

The new standards update those established for worker and general population AELs dating back to 1988. They are designed to protect against adverse health effects due to acute exposures as well as against the risk of cancer from long-term exposure, according to the CDC. In effect, the Army currently does not monitor for long-term, low-level exposure to workers. The new monitoring will not require new monitoring systems, but rather the Army will have to validate its existing approach, known as the depot area air monitoring system (DAAMS), at a lower exposure level than it currently does for short-term exposure, the Army source says.

DAAMS is a passive sampling system that draws air through adsorption tubes, which are collected periodically for analysis; the system is currently used on the perimeter of destruction facilities to ensure exposure limits for the general population are not exceeded. The Army uses a separate near real-time monitoring system for short-term worker exposures.

After receiving comments from four entities - the Army, the states of Colorado and Utah, and an employee union - the CDC backed down from requiring a long-term exposure standard for workers akin to the general population level. Rather than setting a 0.00002 milligrams per square meter (mg/m3) over a time-weighted average of 12 hours, as it had proposed, the CDC is establishing the long-term worker exposure limit at 0.0004 mg/m3 over a time-weighted average of 8 hours. This type of monitoring is already conducted at the perimeter to meet the general population standard, but now the Army will have to add more monitoring stations and analyze more frequently at a lower level to show workers are not being exposed to "very, very low levels" of agent over long periods of time, the Army source says. These additional monitors will be placed inside the destruction plant and in igloos storing the weapons.

This does not necessarily change the way the Army does business, "just how we look at things," the source says.

The Army feared that making the worker protection levels the same as the general population levels would have driven up false positives, in turn lowering workers' confidence in the monitoring system, and unnecessarily delaying the program, the source says.

The CDC retains the same general population limit (GPL) as it proposed last year, the notice says. But it is a factor of five lower than the current GPL, the Army source says. While the Army's systems can detect at that level, it will have to shift its quality control criteria lower by a factor of five, the Army source says. That will take time to prove out, the source says.

And for short-term exposures, the CDC has decided against a proposed five-minute exposure limit, and instead recommends a 15-minute short-term exposure limit or STEL. This is set at 0.003 mg/m3 and is monitored through near-real-time methods. In response to comments, the CDC says in the notice that the proposed five-minute ceiling for the STEL "was overly proscriptive and possibly counterproductive."

The notice says the CDC is issuing the AELs as interim, rather than final, recommendations pending the availability of better data on characterizing the cancer potency of sulfur mustard.