Regulatory frameworks exist to address vital issues related to food safety and environmental protection in regard to GMO applications. However, little research or regulatory oversight currently exists addressing the potential impact of genetically modified/engineered crops on the health and safety of agricultural workers. Some studies have evaluated the health effects of Bt in agricultural workers. In a public health survey, a large number of individuals were exposed to a massive Bt pesticide spraying program. Some of the symptoms reported included rash and angioedema. One of the spray workers developed dermatitis, pruritus, swelling, and erythema with conjunctival injection. Bt was cultured from the conjunctiva in this case. In 1992 the use of Bt as part of an Asian gypsy moth control program was associated with symptoms of allergic rhinitis, exacerbations of asthma, and skin reactions among individuals exposed to the spraying operations. However, no follow-up was performed to determine if these events were a result of hypersensitiv-ity to Bt or possible toxic reactions, or were secondary to common aeroallergens coincidental to the season when the spraying was performed. Similar results were produced during another spraying of Bt in 1994 (82-88).
Given that approximately 75% of asthma cases are triggered by allergens, the potential allergenicity of Bt is important to investigate further. A study by Bernstein et al. (83) measured immune responses in seasonal migrant farm workers exposed to Bt pesticides in the muck crops region of Northern Ohio in the United States in October 1995. This study included questionnaires, nasal and mouth lavages, ventilatory function assessment, and skin tests to indigenous aeroallergens and to a variety of Bt spores and vegetative preparations. The exposure group consisted of farmers who picked vegetables (celery, parsley, cabbage, kale, spinach, and strawberries) that required Bt pesticide spraying soon after the first crops were planted and continuing until the harvesting of the last crop in early October. Positive skin-prick tests to several Bt spore extracts were seen chiefly in exposed workers. Specifically, there was a significant (p <.05) increase in the number of positive skin tests to spore extracts at 1 and 4 months after exposure to Bt spray. The number of positive skin test responses was significantly higher in high-versus low-to-moderately exposed workers. The majority of nasal lavage cultures from exposed workers were positive for the commercial Bt organism, as demonstrated by specific molecular genetic probes. Specific immunoglobulin E (IgE) antibodies were also more present in workers exposed to high Bt spray levels, and specific IgG and IgE levels were present in all groups of exposed workers. However, there was no evidence found of occupationally related respiratory symptoms. Another study by Pearce et al. (87) studied the effects of aerial spraying with the Kurstaki species of Bt on children with asthma within the Bt spray area in Victoria, British Columbia, in 1999. The study found no difference in asthma symptom scores between exposed and gender and age-matched controls either before or after the spray. No significant changes were found for the peak expiratory flow rates for subjects after the spray period.
From a consumer standpoint, concerns have been raised about the aller-genic potential of GM foods. For example, the CDC investigated 51 reports of possible adverse reactions to corn that occurred after Starlink, a corn variety modified to produce a Bt endotoxin, Cry9C, was allowed for animal feed and was found in the human food supply. However, allergic reactions were apparently not confirmed. More research is needed to better comprehend the health effects of Bt and other biological sources such as novel proteins found in genetically modified foods from an occupational, environmental, and consumer perspective (88,89).
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