Challenging conventional risk assessment with respect to human exposure to multiple food contaminants in food: A case study using maize.

•Multiple chemical contaminants threaten the safety of many food commodities.•Cytotoxicity was found at concentrations representing legal limits.•The most cytotoxic mixture was (tertiary mycotoxins plus Cd/As/CP/PM).•Synergy was evident at concentrations contaminating maize above legal limits.

Mycotoxins and heavy metals are ubiquitous in the environment and contaminate many foods. The widespread use of pesticides in crop production to control disease contributes further to the chemical contamination of foods. Thus multiple chemical contaminants threaten the safety of many food commodities; hence the present study used maize as a model crop to identify the severity in terms of human exposure when multiple contaminants are present. High Content Analysis (HCA) measuring multiple endpoints was used to determine cytotoxicity of complex mixtures of mycotoxins, heavy metals and pesticides. Endpoints included nuclear intensity (NI), nuclear area (NA), plasma membrane permeability (PMP), mitochondrial membrane potential (MMP) and mitochondrial mass (MM). At concentrations representing legal limits of each individual contaminant in maize (3 ng/ml ochratoxin A (OTA), 1 μg/ml fumonisin B1 (FB1), 2 ng/ml aflatoxin B1 (AFB1), 100 ng/ml cadmium (Cd), 150 ng/ml arsenic (As), 50 ng/ml chlorpyrifos (CP) and 5 μg/ml pirimiphos methyl (PM), the mixtures (tertiary mycotoxins plus Cd/As) and (tertiary mycotoxins plus Cd/As/CP/PM) were cytotoxic for NA and MM endpoints with a difference of up to 13.6% (p ≤ 0.0001) and 12% (p ≤ 0.0001) respectively from control values. The most cytotoxic mixture was (tertiary mycotoxins plus Cd/As/CP/PM) across all 4 endpoints (NA, NI, MM and MMP) with increases up to 61.3%, 23.0%, 61.4% and 36.3% (p ≤ 0.0001) respectively. Synergy was evident for two endpoints (NI and MM) at concentrations contaminating maize above legal limits, with differences between expected and measured values of (6.2–12.4% (p ≤ 0.05–p ≤ 0.001) and 4.5–12.3% (p ≤ 0.05–p ≤ 0.001) for NI and MM, respectively. The study introduces for the first time, a holistic approach to identify the impact in terms of toxicity to humans when multiple chemical contaminants are present in foodstuffs. Governmental regulatory bodies must begin to contemplate how to safeguard the population when such mixtures of contaminants are found in foods and this study starts to address this critical issue.