Vegetables grown in communities affected by illegal mining may expose consumers to potentially harmful levels of toxic metals, according to a review of 45 scientific studies conducted across Ghana.
The review, published in Environmental Monitoring and Assessment, examined contamination involving lead, cadmium, chromium, mercury and arsenic, focusing on how these elements move from polluted soil and irrigation water into vegetables commonly consumed by households.
The study covered tomatoes, pepper, garden eggs and onions, providing insight into how mining-related pollution could extend beyond rivers and forests to food production and public health.
The research was led by Eric Osei Bonsu, a research assistant and scientist at the CSIR-Crops Research Institute in Kumasi. He worked with co-authors Michael Kwabena Osei, Harry Okyere and James Korang.
Cadmium transfer raises alarm
Drawing on evidence from 11 mining districts, the researchers found that cadmium had the highest soil-to-plant transfer in tomatoes and garden eggs.
Transfer factors above 1.0 indicated that cadmium concentrations in these vegetables could equal or exceed concentrations in the soil in which they were grown.
The review also documented sites where lead, arsenic and mercury concentrations in vegetables exceeded limits established by the World Health Organization and the FAO Codex Alimentarius.
The most striking findings came from some locations in the Ashanti and Western Regions. At the most contaminated sites reported in the reviewed studies, arsenic concentrations reached up to 200 times the relevant limit, while mercury reached up to 400 times the limit.
The researchers further reported that the cumulative hazard index exceeded 1.0 in every mining-adjacent community for which the necessary data were available. Such results indicate a potential non-cancer health concern associated with regular consumption of vegetables from the affected locations.
However, the findings reflect contamination documented at specific sites and should not be interpreted as evidence that all vegetables grown in Ghana are unsafe.
Testing and prevention needed
The researchers said monitoring efforts should prioritise communities affected by mining, with regular testing of vegetables, agricultural soils and irrigation water.
They also recommended washing and handling produce carefully after harvest to reduce metals attached to vegetable surfaces. However, they emphasised that washing cannot remove contaminants already absorbed into plant tissues.
Agricultural buffer zones around mining operations should also be established using local evidence of contamination rather than a uniform distance applied everywhere.
The review highlighted important scientific gaps. Researchers need to distinguish between different chemical forms of chromium and arsenic, improve assessments of the combined effects of multiple metals and undertake long-term human biomonitoring to determine whether contamination in food is reflected in people’s bodies.
The authors’ findings add to concerns about the wider consequences of galamsey, particularly for communities where farming and mining activities occur close together.
Bonsu expressed appreciation to his co-authors and colleagues at the CSIR-Crops Research Institute and the CSIR College of Science and Technology for their contributions.
“Galamsey is usually discussed in terms of rivers and forests. Our hope is that this review places the food on Ghanaian plates firmly within that conversation,” he said.
