Ochratoxin A in airborne dust and fungal conidia

Farm workers are often exposed to high concentrations of airborne organic d ust and fungal conidia, especially when working with plant materials. The p urpose of this investigation was to study the possibility of exposure to th e mycotoxin ochratoxin A (OTA) through inhalation of organic dust and conid ia. Dust and aerosol samples were collected from three local cowsheds. Aero sol samples for determination of total conidia and dust concentrations were collected by stationary sampling on polycarbonate filters. Total dust was analysed by gravimetry, and conidia were counted using scanning electron mi croscopy. A method was developed for extraction and determination of OTA in small samples of settled dust. OTA was extracted with a mixture of methano l, chloroform, HCI, and water, purified on immunoaffinity column, and analy sed by ion-pair HPLC with fluorescence detection. Recovery of OTA from spik ed dust samples (0.9-1.0 mug/kg) was 74% (quantitation limit 0.150 mug/kg). OTA was found in 6 out of 14 settled dust samples (0.2-70 mug/kg). The tot al concentration of airborne conidia ranged from < 1.1 x 10(4) to 3.9 x 15( 5) per m(3), and the airborne dust concentration ranged from 0.08 to 0.21 m g/m(3). Conidia collected from cultures of Penicillium verrucosum and Asper gillus ochraceus contained 0.4-0.7 and 0.02-0.06 pg OTA per conidium, respe ctively. Testing of conidial extracts from these fungi in a Bacillus subtil is bioassay indicated the presence of toxic compounds in addition to OTA. T he results show that airborne dust and fungal conidia can be sources of OTA . Peak exposures to airborne OTA may be significant, e.g., in agricultural environments.