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Study · Journal of environmental quality · 2021

Heavy metals in wheat flour near a lead smelter

Li L, Zhang Y, Ippolito JA, Xing W, Tu C · Free full text

What it found

Wheat grown near a lead smelter in China contained cadmium and lead above the country's food limits, and removing the bran lowered lead most.

The authors estimated that children eating whole wheat flour from the closest village faced the highest risk, mainly from cadmium.

What they found

Metals in wheat fractions

In all samples, metal levels were highest in bran, lower in whole wheat flour, and lowest in white flour. For example, mean cadmium in whole wheat flour was 0.38 mg per kg, and lead was 0.48 mg per kg.

Above Chinese limits

All whole wheat flour samples had cadmium above China's maximum permissible concentration of 0.1 mg per kg, and 95% had lead above 0.2 mg per kg. In white flour, 100% still had too much cadmium, but only 36% had too much lead.

Removing bran cuts lead

Milling away the bran reduced lead in the flour more than any other metal, by an average of 53.7%. Cadmium fell by only 15.6%, copper by 34.4% and zinc by 8.76%.

Risk estimates for children

For children eating whole wheat flour, the hazard quotients were 4.19 for cadmium, 1.06 for copper, 1.53 for lead and 1.07 for zinc. For white flour, they were 3.81, 0.68, 0.70 and 0.98. Values above 1 suggest possible health concern.

Risk estimates for adults

Adults had lower hazard quotients than children. For whole wheat flour, the values were 3.16 for cadmium, 0.80 for copper, 1.15 for lead and 0.81 for zinc; for white flour they were 2.87, 0.52, 0.52 and 0.74.

Distance from smelter

Metals in soil and wheat fell as distance from the smelter increased. The village 1 km away had the highest hazard quotients, followed by 3 km and then 6 km.

What the authors conclude

  • They say that lead smelting has raised cadmium, copper, lead and zinc in local soil and wheat grain, and that cadmium was the metal that accumulated most.
  • They advise that removing the bran cut lead and copper the most, but did not greatly reduce the cadmium risk, so more research is needed to lower cadmium in wheat.
  • They suggest that in the most contaminated areas, the only practical ways to reduce health risks may be to lock up soil metals, switch farmland to non-food crops, or move residents.

How it was done

Wheat is a staple food, and when it is grown on soil contaminated by heavy metals, the flour made from it can be a major source of these metals for people. The authors wanted to see whether whole wheat flour and white flour carry different amounts of cadmium, copper, lead and zinc, and what that means for health.

They collected 13 pairs of soil and wheat grain samples from each of three villages at 1, 3 and 6 km from a large lead smelter in northern China. They milled the grain into whole wheat flour, bran and white flour, measured the metals in each, and used standard formulas to estimate daily intake and health risk for adults and children.

What it can’t tell you

  • The risk estimates assume that all the metal in the flour is absorbed by the body, but the authors note that this likely overestimates the real risk because people absorb only part of it.
  • The study measured metals in wheat and soil from one polluted area in China, so the results may not apply to wheat grown elsewhere.
  • The authors did not measure metal levels in people, so they cannot show what health effects, if any, occurred.

The paper

Title
Lead smelting alters wheat flour heavy metal concentrations and health risks
Type
Study
Summarised from
Full text
Cite
Li L, Zhang Y, Ippolito JA, Xing W, Tu C (2021). Lead smelting alters wheat flour heavy metal concentrations and health risks. Journal of environmental quality. doi:10.1002/jeq2.20198Free full textPubMed 33462853DOI

Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error