Potential for Aerosol Dissemination of Biological Weapons: Lessons from Biological Control of Insects

David B. Levin, Giovana Valadares de Amorim

Disclosures

Biosecur Bioterror. 2003;1(1) 

In This Article

Conclusions

The study of the B. thuringiensis spray in Canada in 1999 provides data that refutes arguments asserting that there are technological barriers that would prevent all but major military programs from using B. anthracis as an aerosol disseminated bioweapon. These findings should be understood by those with responsibility for preventing or responding to the consequences of bioterrorist attacks. These data provide evidence that it is technologically feasible to disseminate biological agents from aircraft (or backpack sprayers, or truck-mounted foggers).[23,24,25,26,27] Forest protection personnel, mosquito control personnel, and farmers have been doing so for over 2 decades. Spray formulations consist of readily available ingredients that can be obtained from agricultural supply stores, and these formulations do not clog spray nozzles. And while most of the droplets in the spray are large, in the range of 100 to 150 microns, a significant amount of small droplet aerosolization occurs. Droplets of 2 to 7 microns are formed in sufficient quantities to penetrate houses and contaminate the nasal passages of residents inside their homes. The concentration of airborne spores indoors increased within a few hours after the spray and ultimately exceeded the outdoor concentration.

This study was designed to provide information concerning human exposure to the Foray 48B spray in order to assess the potential public health impact of spraying with B. thuringiensis. It was not designed, specifically, to answer questions about a potential bioterrorist attack. Therefore, questions relevant to biosecurity remain unanswered: How are droplets of <7 microns generated during the spray application of much larger particles? What is the rate of decrease of airborne spores inside and outside homes and buildings? What is the role of nasal swabs after such exposure, and what role could such tests provide in triage and treatment after exposure? Is there a difference in exposure if the spray is applied by a truck-mounted fogger or from a backpack sprayer, compared with an aircraft? Additional studies would need to be designed and conducted to answer these and other questions that bear directly on biosecurity.

In conclusion, monitoring ongoing routine human exposures to nonhuman pathogens that are applied in urban areas may be our best hope of acquiring more detailed empirical human and environmental data about the potential consequences of aerosol-disseminated bioweapons. B. thuringiensis appears to be an excellent model for aerosol dissemination of B. anthracis. Opportunities to evaluate human exposure to nonhuman pathogens arise in North America every spring and summer, when biological agents are applied to control insect pest populations.

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