Occupational Exposure to Mycotoxins

Grain dusts represent an occupational hazard for a number of reasons including the possibility of the allergic disease hypersensitivity pneumonitis (Farmer's lung), endotoxicosis (toxicosis from exposure to bacterial endotoxin) and organic dust toxic syndrome. Inhalation of mycotoxins contained in airborne dusts is a potential health risk, both from systemic exposure but more importantly for their effects on lung biology.

Understanding how DON and other toxins become air-borne in the grain dust is an important consideration when assessing occupational or human health risks. Many mycotoxin producing pathogenic fungi such as Fusarium graminearum (Gibberella ear rot in corn and Fusarium head blight in wheat) accumulate very high mycotoxin levels in the outer layers of the kernel and the chaff. Damaging the outer layers of wheat kernels or corn seed during the handling, processing or transportation of the grain can release large concentrations of DON and other toxins into the air as grain dust. Grain dusts can also contain large concentrations of mycotoxins from debris (fines, chaff, cob pieces, red dog, etc), fungal material (such as spores and mycelium) and the disintegration of the grain during handling and shipping.

For these reasons, inhalation exposure to DON has been the subject of a number of health hazard studies. Ten years ago, air samples were collected in Canadian grain elevators from handling the heavily contaminated wheat crop in southern Manitoba. We found 0.5 to 5.8 ppm DON + 1 ppm T2 + HT2 toxin in airborne dusts. Finnish workers reported the concentrations of dusts, deoxynivalenol and spores associated with on-farm handing of grains (grain drying, milling, cattle feeding). Deoxynivalenol contents were similar to those we had found in grain from the western crop noted above.

Studies have been conducted in Norway of male and female grain farmers. Norwegian grains are affected mainly by Fusarium head blight and various trichothecenes and culmorins have been reported as common. Perinatal health in woman farmers was at greater risk after harvest and after a poor crop. Occupational exposure to mycotoxins in grain was associated with miscarriage at an early stage of pregnancy and there were small increased relative risks of a number of cancers in female but not male farmers.

Everyone handling mouldy grain has a personal responsibility to be aware of the health hazards associated with mould and mycotoxin contamination, to use appropriate means that emphasize prevention of exposure to mouldy grain and to minimize contamination of facilities, equipment and personnel. Reasonable precautions must be taken to minimize mycotoxin contamination by any route, e.g. oral, inhalation and skin. Procedures need to be in place for handling and disposal of mould-infected material. When screening dust or other small particulates from harvested mouldy grain, be certain to bury the screenings in a remote area away from field crops to minimize later exposure of accidental ingestion of farm animals.

While harvesting, drying, grinding, mixing and transporting mouldy grain and animal feed workers need to remember that inhalation or dermal exposures of mouldy grains, mycotoxin-containing spores and dust can cause allergic reactions (respiratory and skin), lung irritation and toxic exposures. Use protective gloves when handling contaminated material. Wash hands with soap and water after working. Take steps to prevent exposure to dust by handling material under well-ventilated conditions upwind of dusts generated by farm equipment. Under some conditions, it may be appropriate to wearing a mask recommended by local authorities as well as eye protection and coveralls. Increase the fat content of animal diets to reduce dust formation in animal buildings.

Note: this was adapted from a chapter written for a World Health Organization (WHO) publication on mycotoxins in preparation by J. David Miller, Carleton University, Ottawa. Miller is a member of the American Industrial Hygiene Association Environmental Microbiology and Biosafety Committee, participated in the Labour Canada investigation cited below and has expertise on the inhalation, oral and dermal toxicology of mycotoxins.

Literature cited

General background

AAFC (1988) Reducing mycotoxins
in animal feeds. Publication 1827E.
Agriculture Canada, Ottawa. 22 p
(also published in French, Spanish,
Japanese).

Trenholm HL, Prelusky DB, Young
JC, Miller JD (1988) A practical
guide to the prevention of
Fusarium mycotoxins in grain and
animal feedstuffs. Arch Environ
Contam Toxicology 18:
443-451.

Primary literature

De Mers, F. 1994. Preliminary assessment of the risk of exposure to trichothecenes produced by Fusarium graminearum in grain dust. Occupational Safety and Health Branch, HRD, Ottawa.

Kristensen, P., L.M. Irgens, A. Andersen, A.S. Bye, and L. Sundheim, L. 1997. Gestational age, birth weight and perinatal death among births to Norwegian farmers. American J Epidemiology 146:329-338.

Kristensen P, Andersen A, Irgens LM (2000) Hormone-dependent cancer and adverse reproductive outcomes in farmers' families-effects of climatic conditions favoring fungal growth in grain. Scand J Work Environ Health. 26:331-337.

Lappalainen, S., M. Nikulin, S. Berg, P. Parikki, E-L. Hintikka and A-L. Pasanen. 1996. Fusarium toxins and fungi associated with handling of grain on eight Finnish Farms. Atmospheric Environment 30:3059-3065.

Miller JD (1994) Mycotoxins. In: Rylander R, Pettersen Y (eds) Handbook of organic dusts. CRC Press, Boca Raton, FL. p. 87-92.

Rylander R, Pettersen Y (1994) Handbook of organic dusts. CRC Press, Boca Raton, FL

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