Exposure of Rural and Urban Populations in KwaZulu Natal, South Africa, to Fumonisin [B.sub.1] in Maize

Environmental Health Perspectives, March, 2001 by Paul K. Chelule, Nceba Gqaleni, Michael F. Dutton, Anil A. Chutorgoon

We surveyed households in rural and urban areas of KwaZulu Natal, South Africa, to assess the exposure of the inhabitants to fumonisin [B.sub.1] ([FB.sub.1]), a mycotoxin produced by Fusarium verticillioides. In southern African regions maize, used as a staple food by the population, is prone to F. verticillioides infection. Furthermore, high levels of [FB.sub.1] in maize have been associated with esophageal cancer in South Africa. We assessed exposure of the population to [FB.sub.1] at three levels, namely, by analyzing stored maize, plate-ready food, and feces. The positions of participating households in the rural area were recorded using geographic information systems (GIS) for ease and accuracy of follow-up. Of the 50 rural maize samples examined, 32% had levels of [FB.sub.1] ranging from 0.1-22.2 mg/kg, whereas 29% of the 28 cooked maize (phutu) samples contained [FB.sub.1] ranging from 0.1-0.4 mg/kg. The incidence and levels of [FB.sub.1] in feces were 33% and 0.5-39.0 mg/kg, respectively. Of the 49 urban maize samples analyzed 6.1% had a range of 0.2-0.5 mg/kg [FB.sub.1], whereas 3 of 44 fecal samples (6%) ranged between 0.6 and 16.2 mg/kg. No [FB.sub.1] was detected in urban phutu samples. Because these levels are lower than those published from regions in South Africa with high incidence of esophageal cancer, it may be concluded that the risk of esophageal cancer from [FB.sub.1] exposure is lower in the KwaZulu Natal region. Key words: esophageal cancer, fumonisin [B.sub.1], Fusarium verticillioides, high performance liquid chromatography (HPLC), maize. Environ Health Perspect 109:253-256 (2001). [Online 1 March 2001]

http://ehpnet1.niehs.nih.gov/docs/2001/ 109p253-256chelule/abstract.html

Certain mycotoxins have been associated with disease conditions among rural populations around the world, for example, aflatoxin [B.sub.1] and liver cancer (1). More recently, fumonisin [B.sub.1] ([FB.sub.1]) has been associated with the etiology of esophageal cancer in South Africa (2), and this has been supported by immunolocalization of [FB.sub.1] in esophageal cancer tissue (3). Fusarium verticillioides (mating type A), a producer of [FB.sub.1], has been identified as a major fungal contaminant on maize, especially in the homegrown crops intended for human consumption (4). The degree of maize infection is highly dependent on environmental factors, such as average temperatures below 22 [degrees] C and frequent rain during the first 2 weeks after silking, which increase the risk of colonization by Gibberella fujikuroi.

Because maize is the staple diet of the South African rural population, there is an increased risk of consumption of fumonisins. Studies carried out in four districts of Transkei, South Africa, linked high esophageal cancer rates in Butterworth and Kentani to the consumption of maize contaminated with elevated levels of [FB.sub.1] (117.3 mg/kg in 1989) as compared to lower levels in the control areas (Bizana and Lusikisiki; 11.3 mg/kg) (5). F. verticillioides was found to be the most dominant fungus infecting commercially produced maize in South Africa (6). In this case, the urban population may not be spared from [FB.sub.1] exposure.

We wanted to know whether other rural and urban populations of KwaZulu Natal, South Africa, are exposed to [FB.sub.1] at the same level as in the Transkei. Our study was carried out in Durban Metro and in villages of Mphise and Ngcolosi, a rural area near Kranskop, KwaZulu Natal, to determine the level of [FB.sub.1] in raw (stored) and cooked food. The analysis of fecal samples was also carried out as a short-term marker for exposure to [FB.sub.1] (7).

The use of geographic information systems (GIS) in health has been applied to epidemiologic investigations in South Africa, including malaria (8,9). In this study, we used GIS to locate and plot the rural dwellings for identification and follow-up sampling.

Materials and Methods

Chemicals. All chemicals, unless otherwise specified, were of Analar Grade. SPE SAX and [C.sub.18] cartridges containing 500 mg sorbent (10 mL capacity, Varian Bond-Elut) were purchased from Analytichem (Harbour City, CA, USA). For the mobile phase, we used methanol:0.1 M sodium dihydrogen phosphate (80:20, v/v) adjusted to pH 3.4 with orthophosphoric acid. o-Phthaldialdehyde (OPA) reagent was prepared by dissolving 40 mg OPA in 1 mL methanol and diluting with 5 mL 0.1 M sodium tetraborate and mercapthoethanol (50 [micro]L). Solvents used included acetonitrile/water (1:1, v/v), butanol, acetic acid, and methanol, all obtained from BDH Chemicals, Poole, England. o-Phosphoric acid (concentration [is greater than] 85%) was obtained from BDH Chemicals, Poole, England. We obtained the [FB.sub.1] standard (10 mg in sealed glass vials) from PROMEC, Cape Town, South Africa. The [FB.sub.1] standard was dissolved in acetonitrile/ water (1:1v/v) to give 1 mg/mL and 50 [micro]g/mL [FB.sub.1] working solutions.

Ethical approval We obtained ethical permission for the study from the Ethics Committee of the University of Natal (Nelson R. Mandela Medical School, H194/97). We also obtained informed consent from the clients before they were recruited into the study.