Study to contain Kenya’s aflatoxin contamination in maize

Funded by the Bill & Melinda Gates Foundation, the project in Kenya is led by the International Food Policy Research Institute (IFPRI) with partners from ACDI/VOCA, the International Maize and Wheat Improvement Center (CIMMYT), and the Kenya Agricultural Research Institute (KARI).
Aflatoxin is a naturally occurring carcinogenic by-product of fungi that colonize certain crops, including maize, the main dietary staple of Kenyans. Contamination starts in the field and is exacerbated when crops are damaged by drought or insect infestation, or when produce comes into contact with soil and is not properly dried. Contamination is often unavoidable, and many African countries, including Kenya, do not regularly test maize for aflatoxins, leading to the sale and consumption of contaminated and suspect grain. “In many developing countries, widespread subsistence farming systems, lack of irrigation, and inadequate drying and storage facilities impede the prevention and detection of aflatoxin in crops,” said Clare Narrod, IFPRI senior research fellow and project leader. “Consequently, many people are chronically exposed to aflatoxins in their food and are at risk of serious health problems.” Acute exposure to high levels of aflatoxins can result in liver failure and rapid death. Chronic exposure, in both humans and animals, exacerbates infectious diseases and can lead to cancer, liver cirrhosis, weakened immune systems, and stunted growth in children.

To determine the extent of aflatoxin contamination in maize, researchers from CIMMYT and KARI have been collecting samples along the entire value chain in eastern and south western Kenya—from farmers’ fields at harvest time, postharvest storage sites at the farm, and traders at markets and posho mills. The study is finding that aflatoxin contamination is more widespread than previously thought, occurring in both eastern and south western sites. In eastern study sites, 31 percent of samples collected from farmers’ fields in February 2010 had aflatoxin levels greater than 10 parts per billion (ppb)—the maximum level allowed by the Kenyan government, as well as the United Nations World Food Programme, in maize that is intended for human consumption.
In south western sites, 40 percent of samples from farmers’ fields in the same period had aflatoxin levels above the legal limit of 10 ppb. Contamination levels were higher in the maize stored by farmers after the harvest. Thirty-eight percent of samples from farmers’ stores in eastern Kenya and 60 percent from south western Kenya, all collected between February and May 2010, had aflatoxin amounts greater than 10 ppb. Contamination levels varied from 0 to 1700 ppb in eastern Kenya and from 0 to 600 ppb in south western sites. Contamination levels vary considerably between farmers and villages, as well as between regions. Levels in eastern Kenya region ranged from 0 to 1400 ppb, while in south western sites, concentrations ranged from 0 to 700 ppb. The study is also finding differences in contamination levels from season to season: there was little or no contamination in samples taken from farmers’ fields in south western sites in 2009, in sharp contrast to 2010. Identifying the causes for this variation will be very important to identifying strategies to reduce contamination and target areas or seasons at higher risk. In samples collected from markets between February and May of 2010, average levels of contamination were high in eastern areas, where maximum aflatoxin amounts were 163 times greater than the level safe for consumption.

Almost 10 percent of all south western maize samples were also unfit for human consumption. Based on informal interviews, the study found evidence of little or no testing for aflatoxin in Kenyan markets, although the government has recently stepped up testing in high risk areas.

Although farmers in eastern Kenya are aware of the aflatoxin problem, many still continue to thresh grain on bare soil and have poor storage facilities. Efforts are being made in some areas to educate farmers on methods to reduce contamination, including better management of crop production, timely harvesting, using raised platforms to dry grains, and improved storage techniques, such as applying pesticides and using metal silos. Researchers are seeking to better understand the causes of the aflatoxin contamination and to identify cost-effective techniques to reduce the risk.

“The prevalence of aflatoxins in maize in various regions of the country, including low-risk areas, underscores the importance of raising awareness of the chances and consequences of chronic exposure to the toxin among producers, consumers, traders, and vendors,” said Steve Collins, country director and chief of party, ACDI/VOCA. “The serious economic and health implications of aflatoxins also highlight the critical need to provide farmers and consumers with affordable strategies to reduce contamination and incentives to use existing mitigation technologies, new uses for contaminated grain, and alternative sources of food when maize is unsafe to eat.”, he added.

Although relatively low-cost technologies are currently available to prevent or detect aflatoxin contamination, their use in Kenya is not widespread for a number of reasons, including limited awareness of the problem and potential solutions, decline in available farmland and the impossibility of crop rotations, and lack of adequate infrastructure for optimal drying, storage, and testing.

“This study shows that the aflatoxin problem is complex and multifaceted,” said George Mahuku, senior scientist, CIMMYT. “Any effective response requires participation from all stakeholders along the value chain, including farmers, traders, government officials, and policymakers. There is a need for cheap, affordable, and rapid systems to detect maize with aflatoxin levels above the legal limit and to build awareness among stakeholders on the causes and effects of Aflatoxin contamination. Developing new and inexpensive technologies for rapidly drying maize is also important to tackling the aflatoxin problem.” “By better understanding the obstacles as well as the opportunities to prevent and mitigate aflatoxin contamination—from farmers’ field to sellers’ stalls—we hope to improve the health of individuals, the economic wellbeing of households, and national food security,” concluded Pippa Chenevix Trench, IFPRI research fellow and project manager.