Researchers at the University of Ilorin (UNILORIN) have raised concerns over the possible contamination of commonly consumed foods during milling, saying metallic particles released from cast-iron grinding discs could pose long-term health risks.
The researchers found that as much as 1.7 grammes of metallic contaminants could be introduced into 10 kilogrammes of ground maize during dry milling.
The study, funded by the Tertiary Education Trust Fund (TETFund) under its National Research Fund, examined the levels, sources and potential health implications of metallic contamination associated with grinding discs used in food processing.
According to the researchers, the average size of the metallic particles was about 43 micrometres, making them small enough to become mixed with food and pass unnoticed into the digestive system.
The team, led by Prof. Sulaiman Abdulkareem of the Department of Mechanical Engineering, said dry grinding generated substantially more metallic contamination than wet grinding because water acts as a lubricant and reduces wear.
The researchers also found that concentrations of lead, cadmium and arsenic in milled maize exceeded permissible limits established by the Codex Alimentarius Commission.
While their assessment showed that immediate non-cancer health risks were not significant, the researchers warned that prolonged exposure and accumulation of toxic elements could become a serious concern.
Children were identified as particularly vulnerable, with the study estimating that they could face health risks 9.3 times higher than adults.
The researchers said dietary intake accounted for more than 94 per cent of the assessed non-cancer risk and over 97 per cent of cancer risk, highlighting food consumption as the major exposure pathway.
They further identified other possible sources of contamination, including vehicle emissions, agricultural chemicals, manure, zinc-enriched fertiliser, industrial wastewater used for irrigation, oil leakage and leaded-fuel combustion.
The team recommended stricter quality-control standards for grinding discs, greater adoption of wet milling and the use of ferrochromium-alloyed discs by local foundries.
They also proposed magnetic devices capable of removing metallic particles from processed food, alongside greater public awareness and further research into the long-term health effects of exposure.
The researchers said the measures could be implemented with locally available materials and existing foundry technology, contributing to safer food-processing practices.
