Mold in Maize: Less Exposure May Mean Less Cancer.

Mold-produced toxins have tainted food crops probably since the beginnings of agriculture. These mycotoxins can occur when certain molds infect food crops before or after harvest. Both humans and animals are vulnerable to poisoning through consumption of contaminated foods, with acute or chronic illness--including cancer--a potential result. A study by Paul K. Chelule of the University of Natal in Durban, South Africa, and colleagues focuses on the link between exposure to fumonisin [B.sub.1], a mycotoxin produced by Fusarium verticillioides, and risk of esophageal cancer [EHP 109:253-256].

In the 1980s, researchers from the Medical Research Council of South Africa discovered a highly suggestive link between esophageal cancer and exposure to fumonisin [B.sub.1]. Because F. verticillioides infects maize, a staple crop throughout the world, large populations may be exposed to fumonisin [B.sub.1]. The work initiated in the 1980s focused on the high incidence of esophageal cancer in certain districts of the Transkei region of South Africa. A key difference between these districts and control areas was that maize in the areas with high cancer rates was highly contaminated with fumonisin [B.sub.1]. Similar observations were later made elsewhere, notably in China.

The study by Chelule and colleagues looks at fumonisin [B.sub.1] exposure among urban and rural populations in KwaZulu Natal province. The researchers wanted to see how fumonisin [B.sub.1] exposure among people of KwaZulu Natal compares to that of the Transkei populations, which could indicate whether their potential risk for esophageal cancer is as high. The researchers conclude that the KwaZulu Natal populations encounter lower levels of fumonisin [B.sub.1] contamination overall, although rural people have a greater risk of exposure than urban ones.

Eighty-four people took part in the study, 44 from the Durban metropolitan area and 40 from the Tugela Valley, a rural area about 200 kilometers north of Durban. The researchers collected samples of unprocessed maize and sorghum from each person's home, as well as prepared foods including phutu (cooked milled maize), amahewu (a nonalcoholic fermented gruel-like drink made from maize), and isizulu (an alcoholic fermented drink made from maize and sorghum). Fecal samples were also collected from study participants.

The differences observed between unprocessed rural and urban maize samples were significant. Not only were a higher percentage of rural samples contaminated (32% compared to 6%), but the level of contamination was also greater, as determined by chemically extracting fumonisin [B.sub.1] from the food and drink samples and analyzing the quantity extracted. This finding translates to the rural population having a 6 times higher risk of fumonisin [B.sub.1] exposure--and potential consequences--than the urban population, say the researchers. However, they note that even the highest mycotoxin level found in this study, 22.2 milligrams per kilogram of grain, falls far short of that measured in the Transkei study, which exceeded 117 milligrams per kilogram. None of the sorghum samples from either urban or rural areas contained detectable amounts of fumonisin [B.sub.1], and among the cooked foods only rural phutu was contaminated. Of the rural fecal samples, 33% had measurable amounts of fumonisin [B.sub.1] as compared to 7% of the urban samples. The researchers note that fecal analysis provides a useful short-term indicator for fumonisin [B.sub.1] exposure.

The researchers conclude that the people of KwaZulu Natal have a lower risk of fumonisin [B.sub.1] exposure and the potentially related esophageal cancer than the people of Transkei. They attribute urban-rural differences in this study to a more varied diet and greater likelihood of food safety regulations in urban areas. Further, given that sorghum is less prone to contamination, they suggest that their results might encourage cultivating sorghum rather than maize in the Tugela Valley. However, they caution that further study is necessary before taking such a step.