To combat a potential gypsy moth infestation, the Washington State Department of Agriculture is planning to undertake aerial pesticide spraying of a 100 acre site of the Madison Valley area in Seattle in late April and May 2006. The pesticide which will be used, Foray 48B, contains the bacteria Bacillus thuringiensis kurstaki, or Btk. The area is bordered by 21st Avenue East, East Republican Street, Martin Luther King Jr. Way, and East Howell Street.
Bacillus thuringiensis species are naturally-occurring soil bacteria that produce toxins selective for various species of insects. In the case of Btk, the -endotoxin is toxic to gypsy moth larvae. Published data on acute toxicity to humans exposed through the oral and respiratory routes suggest that toxicity of Btk to humans and animals is extremely low to negligible. For more information, see the National Pesticide Information Center website at: npic.orst.edu/factsheets/BTgen.pdf and npic.orst.edu/factsheets/BTtech.pdf
More than 100 million pounds of Btk are used each year to control agricultural pests in the United States, including use by commercial landscapers, organic farmers and gardeners. Several surveillance studies have looked for health problems in persons living in areas where aerial spraying of Btk occurred; none have been able to link Btk to human illness. The most comprehensive study of Foray 48B was done by the Capital Health Region in Vancouver, British Columbia.
This study included a case-control analysis of 29 asthmatic children, a health survey of adults, monitoring of physician and emergency department visits, laboratory-based surveillance, and environmental exposure measurements before and after the spraying. Interestingly, the investigators documented the Foray 48B strain of Btk on fruits and vegetables in local supermarkets, as well as in the nares of children within the spray zone, before the spraying began.
There was no change in any of the health indicators monitored, including peak expiratory flow rates in asthmatic children. One child had an exacerbation of asthma during the study period. Persons calling a health complaints hotline reported headache, shortness of breath, redness, itching, and burning of the eyes, stuffy or runny nose, sore throat, upset stomach or nausea, and a metallic taste. However, no differences in symptoms were found between 522 persons living inside the spray zone and 487 persons living outside the spray zone.
Laboratory-based surveillance for pesticide strain of Btk infections in Oregon after spraying did not implicate Btk in any human illness. Isolates that were recovered were considered contaminants in most cases.
Public Health and the WA State Department of Health monitored health-related complaints after aerial spraying with Foray 48B of the Ballard and Magnolia neighbor-hoods in Seattle in 2000. Fifty-nine complaints were received, which included mostly complaints of cough, headache, trouble breathing, sore throat, nasal congestion, and irritated eyes. Fourteen persons sought some kind of health care for symptoms. While it was not possible to epidemiologically link these symptoms to the aerial spraying, many affected residents felt that their symptoms were due to the spraying. For more information, please see: www.doh.wa.gov/ehp/ts/Pest/AsianGypsyMothReport.pdf
In addition to Btk, the pesticide Foray 48B contains "inert" ingredients that are proprietary and cannot be revealed to the public. The U.S. EPA as well as the WA Poison Control Center have reviewed the list of inert ingredients and have concluded that the pesticide product, including the inert ingredients, has little to no toxicity.
Despite the lack of evidence for serious adverse health effects related to Foray 48B, we cannot conclude that there is no risk for unanticipated, less serious or infrequent health effects, particularly in persons who may be sensitive to the pesticide formulation. It is possible that some persons sensitive to inhaled allergens or irritants will experience allergic symptoms, respiratory irritation, or rash during the time of the Btk application, although it is not known that such symptoms are related to Btk spraying.
To minimize any chance of real or perceived adverse health effects, Public Health is recommending that all persons in the spray area minimize exposure to the pesticide at the time of the application by remaining indoors for 30 minutes after the application.
In particular, persons who have underlying illnesses that make them more susceptible to infections and respiratory irritation, such as leukemia, AIDS, other immune deficiencies, or who are receiving radiation or chemotherapy treatment or who have asthma, emphysema, or allergic sensitivities should review the following precautions:
To report suspected or confirmed pesticide related illness or discuss potential adverse health effects, call the WA Poison Control Center at 1-800-222-1222, or the WA State Department of Health Pesticide Program at 1-888-586-9427, M-F, 8 AM - 5 PM.
For information about spraying, and to request to be notified of the exact dates and times of the spray application call the WA Department of Agriculture Gypsy Moth Hotline at 1-800-443-6684.
Physicians managing possible adverse reactions to Foray 48B can call the manufacturer’s 24-hour technical support line at 1-800-323-9597, through which specific ingredients may be released if medically necessary.
Additional information Health Advisories & Resources and the public is available on the Public Health website at: www.metrokc.gov/health/env_hlth/gypsy.htm or by calling 206-205-4394. Recorded information about gypsy moth spraying can be heard on our hotline at (206) 296-4949.
