Report assesses health risk of pesticide exposure to U.S. troops

WASHINGTON, January 9, 2001 (GulfLINK) - The Office of the Special Assistant for Gulf War Illnesses released today an environmental exposure report examining the use, and potential long-term health effects, of pesticides during the Gulf War. Some Gulf War veterans have reported a wide array of unexplained illnesses that many suspect may be related to their use of and exposure to pesticides during the war. The results of the health-risk assessment conducted by investigators suggests that exposure to some pesticides may be a cause for some of the illnesses reported by some veterans.

Based on the experience of past campaigns fought in the region, preventive medicine personnel anticipated the need to control pests in the Persian Gulf - especially sand flies and mosquitoes. These insects carry several infectious diseases, including leishmaniasis, sand fly fever and malaria. Because sand fly fever had been widespread in Iran and Iraq during World War II, U.S. health officials viewed it as one of the most serious infectious disease threats. Of the 697,000 U.S. servicemembers deployed during the Gulf War, only 40 cases of infectious diseases transmitted by insects have been reported in the published literature. Military analysts attributed this low incidence of insect-borne infectious diseases to the establishment of a comprehensive preventive medicine structure, favorable weather, dry desert locations for most units, and pesticide use.

During the Gulf War, U.S. forces reportedly used, or had available for use, at least 64 pesticide and repellant products to provide protection from insects, rodents and other pests. These included a variety of products such as sprays, powders, baits, pest strips and flypaper. The pesticides and repellents used belonged to five major categories: organophosphorus pesticides, such as malathion and chlorpyrifos; carbamate pesticides, such as bendiocarb; organochlorine, lindane; pyrethroid pesticides, such as permethrin; and insect repellent such as DEET.

"In general, the pesticides and repellents used at the time of the Gulf War were approved by the Environmental Protection Agency and the Food and Drug Administration for general use, and were not considered harmful when used according to instructions." said William Shaughnessy, an environmental science expert for the office for Gulf War illnesses. "Since then, two - diazinon and chlorpyrifos - are being phased out by the EPA for use within the general population."

Some pesticides such as the azamethiphos-based fly bait were purchased locally by authorized personnel for unit use or by individuals for their personal use and may not have been registered with the EPA.

Based on a thorough analysis of available data, investigators focused their investigation on the 12 active ingredients contained in 15 pesticides of potential concern. Investigators believed these pesticides posed the greatest potential hazard to U.S. servicemembers based on prevalence of use, manner of use and toxicity.

"One of the problems we encountered during our investigation was that there weren't a lot of data available on the amounts or types of pesticides used, what was shipped and how they were applied," said Shaughnessy. "There was no monitoring of pesticides or testing done to determine the concentration of pesticides in the environment. Without those data, it is extremely hard to determine the concentrations of pesticides to which individuals were exposed."

Investigators were able to find material-ordering data, but not actual usage data. In the absence of sampling data and pesticide application rates, they relied on information from approximately 700 interviews with preventive medicine personnel to determine exposure levels. Of these interviews, 252 provided specific information related to exposure, such as frequency with which a pesticide was applied, application rates, and personal protective equipment worn. Another 60 interviews provided more general information relating to exposure issues. Another survey of 2,005 veterans, conducted by the RAND Corporation, was used to elicit information about veterans' personal use of pesticides and those they observed others using.

Absorption through the skin is considered to be the most frequent means of pesticide exposure, although pesticides can also enter the body through inhalation or ingestion. The most noticeable effects of acute exposure are slight nausea, mild headaches and some throat irritation. Only one documented case of pesticide exposure resulting in an adverse health effect was found during the course of the investigation. There were, however, several anecdotal reports by several Gulf War veterans that they sought medical treatment due to exposure to pesticides while in the Gulf.

"We believe that specific groups of people, because of their jobs, were at a greater risk to experience overexposure to some pesticides," said Shaughnessy.

The select groups of military personnel most likely to have experienced a greater amount of pesticide exposure included trained and certified pesticide applicators, field sanitation teams, and military police who conducted delousing operations.

Some members of the general military population may also have been overexposed. For example, RAND surveyors estimate that seven percent of servicemembers in the Gulf may have been exposed to pest strips hung in various indoor locations to control flying insects. Sometimes more pest strips than manufacturers recommended were hung in some eating areas and latrines. Furthermore, even when used as directed at the time, because servicemembers spent long times in areas where pest strips were hung, some exposures may have been above levels of concern. Shaughnessy says the special assistant's office estimates that approximately 30,500 servicemembers may have been at a greater risk for short-term health effects because of their exposure to pest strips.

Fly baits, purchased locally and issued by the military may have been used in any of the areas where personnel worked, ate and slept and were often placed in open containers inside and outside buildings and tents, or spread on the ground. Military guidance and labels on the EPA-registered products authorized outdoor use only. In
the health-risk assessment - a hypothetical analysis - OSAGWI estimated that some servicemembers involved in distribution of the pesticides could inhale the pesticide dust, absorb the pesticide contacting their skin or ingest the pesticide via unintentional hand-to-mouth contact.

Besides trained pesticide applicators, the investigators identified three groups of Gulf War veterans who could have been at higher-than-typical risk of overexposure to pesticides. These included those who were exposed to pest strips and to uncontrolled use of fly baits. It also included those whose duties were expanded to include applying pesticides but who lacked sufficient training or protective equipment. Some veterans also reported that they had worn flea and tick collars designed to be used on pets.

"We knew from veterans interviews that in the early days of the conflict, many servicemembers used flea collars as a means of pest management," Shaughnessy said.

"There were some reports of local skin reactions, but we don't believe anyone would have absorbed large amounts of the active ingredients through their skin," he continued, adding that the daily dose would be very low because of the slow release of the active ingredients and the small amount of skin exposure.

Inhaling vapors from flea collars would not have been a significant exposure route for most who used the collars, he said, with the possible exception of the few who wore them around their necks.

To aid in determining the extent of health effects from pesticide exposure, investigators prepared a peer-reviewed health risk assessment. The purpose of the health risk assessment was to provide a hypothetical estimate of the likelihood and magnitude of health effects from pesticide exposure during deployment. Such effects would have been limited to the time of deployment and may not have implications for long-term health effects.

The report stressed that the results of the health risk assessment alone do not prove either that overexposures occurred during deployment, or that any connection exists between pesticide exposures and chronic health effects months or years after exposure. But investigators noted that some groups may have been exposed to concentrations of pesticides which exceeded conservatively derived, risk-based levels of concern, and that because of the overall lack of data, there is not enough evidence to rule out possible long-term effects resulting from exposures to pesticides during the Gulf War deployment.

An independent scientific literature review of the possible health effects of pesticides was completed by RAND. It suggests, but is not conclusive, that pesticides, specifically acetylcholinesterase inhibitors such as organophosphates and carbamates, could be among the potential contributing agents to some of the undiagnosed illnesses reported by Gulf War veterans. The RAND study includes reports of known pesticide exposures and doses and the related health outcomes. RAND investigators combined this review with information from EPA and other sources to produce a health effects analysis. The RAND study says it is unlikely that exposure to these pesticides is the sole explanation for the myriad of health problems reported by Gulf War veterans, since few veterans' symptoms are uniquely characteristic of pesticide exposure alone.

Analysts say an important question regarding organophosphate and carbamate pesticides is: If individuals had no signs or symptoms at the time of exposure, how likely is it that such exposures could result in adverse health effects months or years later?

There is no simple answer that can be given with a high level of confidence, as there is conflicting information in the literature on this subject. The relevant information comes mainly from published studies of civilian pesticide handlers in the U.S. and foreign countries.

Some reports in the literature suggest that unless individuals had signs and symptoms of serious pesticide poisoning or toxicity at the time of the initial exposure, health effects months or years later are unlikely. However, according to the RAND literature review for pesticides, there is also evidence of modest long-term effects following repeated asymptomatic exposures. This issue can be resolved only by further research.

What we do not know, and where more research needs to be done, is work to more accurately and completely characterize exposures to pesticides by military personnel, Shaughnessy said. This is an important consideration for future deployments. We need to ensure that we can to quantify the exposure of soldiers to the pesticides used.

The OSAGWI report's recommendations include a detailed review of the diagnoses contained in the approximately 28,000 Gulf War inpatient records maintained at the National Personnel Records Center in St. Louis, Mo. This would entail identifying and analyzing those records which might be related to pesticide exposure, and following up with personnel who were hospitalized for possible pesticides exposures to determine the current status of their health.

The recommendations also cited the need for a detailed study comparing the exposure assessment results in their health risk assessment with estimates and measurements from other published pesticide studies, and an epidemiological study of current and past military pesticide applicators, assessing their levels of pesticide exposure and any reported health effects.

Investigators from the special assistant's office also identified several lessons learned during the course of their investigation. The recommended areas for improvement include increased monitoring of host nation pesticide application, revised delousing procedures, improved training and supply distribution, formalized local purchase procedures, increased emphasis on personal protective equipment, revised record-keeping procedures, and more thorough occupational health surveillance.

"If you have health concerns, I encourage you to schedule an appointment with either the DoD's Comprehensive Clinical Evaluation Program or the Department of Veterans Affairs' Persian Gulf Registry. Don't tough it out," said Bernard Rostker, the special assistant.

Veterans desiring a free, in-depth medical examination should call the CCEP at (800) 796-9699 or the Department of Veterans Affairs' Persian Gulf Registry toll-free number at (800) 749-8387 to enroll.

The entire environmental exposure report can be read on GulfLINK. This is an interim report, and anyone with information that might impact its findings is encouraged to contact the office by phone at (800) 497-6261 or by e-mail at: