Aflatoxins contamination in raw and locally processed cashew nuts and the associated human health risks:
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Date
2022
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Sokoine University Of Agriculture
Abstract
Aflatoxins (AFs) are one of the mycotoxins which are secondary metabolites of various
fungi species; Aspergillus flavus, A. parasiticus and A. nomius. There are about eighteen
types of aflatoxins that have been identified, but only four are found in food and feed: B 1 ,
B 2 , G 1 and G 2 . Aflatoxin B 1 is the most toxic and classified as group one carcinogen.
Aflatoxins cause serious health problems and have high potential effects on liver cancer,
therefore, numerous investigations have been conducted worldwide. The aim of this work
was to determine the contamination levels of raw and roasted cashew nuts sold in Masasi
and Newala districts of Mtwara region in Tanzania, evaluate the factors associated with the
contamination and estimate human exposure to aflatoxin through consumption of
contaminated cashew nuts. Determination of total aflatoxins levels in raw and roasted
cashew nuts samples was carried out at Tanzania Bureau of Standards (TBS) food
laboratory in Dar es Salaam by using immuno-affinity high performance liquid
chromatography. A total of 60 samples were collected and the highest concentration of
aflatoxins recorded for raw cashew nuts was 3.29 μg/ kg in Masasi and 3.24 μg/kg in
Newala. None of the samples had total aflatoxins contamination greater than the
recommended maximum residues of 4 μg/kg set by European Commission (2010) or 10
μg/kg set by FAO and WHO. All roasted cashew nut samples had total aflatoxins less than 3
μg/kg while about 86% of raw cashew nut samples had total aflatoxins less than 3 μg/kg.
The overall results of the tested samples indicated that the rate of contamination was very
minimal for cashew nuts especially roasted nuts but raw cashew nuts showed higher
contamination. A cross-sectional survey was conducted to assess awareness among cashew
nuts stakeholders (smallholder farmers, traders and consumers) on aflatoxins contamination,
demographic characteristics, handling practices and eating habit. The study showed that the
cashew nuts value chain is highly dominated by females (64%), whose education level was
primary school (58%). Very few respondents (<20%) in either category have heard ofiii
aflatoxins in their lifetime or almost all were among those who have had either a secondary
school or a college level of education. This study revealed that education level of the
respondents was directly related to aflatoxins awareness.
The human exposure to aflatoxin through consumption of contaminated cashew nuts in the
study area was also estimated, whereby data on the rate of consumption was obtained
through a structured questionnaire which involved 120 respondents. The results were used
to calculate the Estimated Daily Intake (EDI) and the Hazard Index (HI). The risk
assessment for aflatoxins was evaluated by the qualitative Margin of Exposure (MOE)
approach and the quantitative hepatocellular carcinoma (HCC) risk approach. The estimated
cancer risk of hepatocellular carcinoma (HCC) in this study ranged from 0.006 to 0.394
cancers per year per 10 5 individuals, upon consumption of cashew nuts with aflatoxin B 1
greater or equal to LOQ to highest contaminated samples, respectively. Since roasted
cashew nuts which have less contamination level are highly consumed than raw (more than
50%), exposure to aflatoxins is very minimal to cashew nuts consumers. Although
estimation of the margin of exposure and risk HCC revealed that cashew nuts, may pose
health risks to consumers depending on the rate of consumption of the contaminated cashew
nuts and the amount consumed.
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Keywords
Aflatoxins contamination, Processed cashew nuts, Human health risks, Masasi-Districts, Newala-Districts