The poison that may be on your dinner table

South Africans may soon have more to worry about than the price of rice.

A new study published in The Lancet Planetary Health has found that climate change is driving up levels of arsenic in rice grown across Asia, the very regions that supply more than 90% of South Africa’s rice imports.

The research, led by a team of international scientists, combined field experiments with climate modelling to show how hotter temperatures and shifting water patterns in rice paddies cause the grain to absorb more arsenic.

The health risks are significant: long-term exposure is linked to cancers, heart disease and developmental problems in children.

For a country like South Africa, which produces very little of its own and relies on imports from Asian countries, this is a red flag.

According to trade data, South Africa imported more than 1.2 million tons of rice in 2022, mostly from Thailand and India.

The country produced only around 3.08 thousand tonnes of rice in 2022, about 0.26% of national consumption, according to Food and Agriculture Organisation-based data.

Essentially, South Africans are mostly eating Asian rice. If climate change is contaminating that rice with arsenic, it becomes our health problem too.

To arrive at these findings, scientists grew rice in controlled test fields where they manipulated water and temperature levels to mimic the hotter, wetter and more erratic conditions predicted for much of Asia.

They found that under warmer conditions and changing irrigation practices, rice plants absorbed significantly more arsenic from the soil and water.

The experimental data were then fed into large-scale climate–crop models that project how rice cultivation will respond to rising global temperatures over the next few decades.

The models consistently showed that by mid-century, arsenic concentrations in rice grains could rise sharply, especially in South and Southeast Asia, the world’s rice bowl.

Health risks in the grain

Why does this matter? Arsenic is a toxic element that occurs naturally in some soils and groundwater. When absorbed by rice, it accumulates in the grain that people eat.

Chronic exposure to arsenic is linked to cancers of the skin, bladder and lungs, as well as heart disease and developmental delays in children.

The researchers estimate that under high-emissions climate scenarios, the health risks from dietary arsenic could rise dramatically across Asia, where rice is eaten daily and in large quantities.

It’s something of a pain to write this kind of article because the media and scientists have been blamed for being alarmists when reporting on the impacts of climate change.

However, keeping these sorts of research findings would be a bigger disservice. The most important point is what should be done to avert climate-inspired disaster?

South Africa’s food safety regulations establish limits on pesticide residues and microbial contamination in imports, but there is limited routine monitoring for heavy metals such as arsenic.

That needs to change, as climate change forces certain environmental issues on food and other consumables.

If we are importing the bulk of our rice from Asia, where the risks are projected to rise, then South Africa must strengthen testing at the ports of entry. Otherwise, we could be looking at a slow-burn public health crisis.

Rice plays a relatively minor role in South African diets, both in terms of quantity consumed and caloric intake.

Maize remains the staple, followed by wheat, with rice trailing significantly behind. This may be some good news, but consumption is growing.

The Lancet study also points to solutions. Farmers in Asia could adopt alternative irrigation practices, such as intermittent flooding rather than continuous submersion, to reduce arsenic uptake.

New rice varieties that resist heavy metal absorption are under development. But these are long-term measures, and South African consumers are unlikely to see immediate protection.

In the meantime, it would be ideal to diversify away from rice to limit consumption. South Africa has strong traditions of eating maize. Encouraging a return to those staples could reduce both dependence on imports and exposure to arsenic.

For households already stretched by rising food prices, that may be easier said than done.

But with climate change rewriting the rules of food security, the rice on South Africans dinner tables may no longer be as safe as it once seemed.

• Dr Enock Sithole is the executive director of the Institute for Climate Change Communication.