Lead Leaches Into Food From Locally Made Aluminium Pots: icddr,b–Stanford Study

Lead can leach into food from locally made aluminium cooking pots. The amount of lead found in food was highest when a new pot was used for the first few times, and even after repeated use the lead in food did not fall below safe levels.

These findings come from a study by the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b) and Stanford University in the United States, published in the Nature group's Journal of Exposure Science and Environmental Epidemiology. The details were shared in a press release sent to the media by icddr,b on Thursday.

The researchers say many aluminium cooking pots are made locally by melting old scrap metal. If that metal is not properly tested, lead can remain in the finished pots, and food cooked in them can then carry lead into the human body.

The risk is especially worrying for children, because lead exposure can have long-term negative effects on children's brain development, learning ability and behaviour. According to the World Health Organization, there is no level of lead in blood that can be called completely safe.

In Bangladesh, it is common to exchange old aluminium pots for new ones, or to take cooking pots in exchange for old clothes. The study did not directly examine that exchange practice, but its results show there is no reason to assume a pot is safe merely because it is new or looks shiny.

The study measured how much lead can pass into food from locally made aluminium pots, and also analysed how food acidity, the way pots are cleaned and the style of cooking affect the amount of lead released.

The researchers collected seven used pots from Bangladeshi households and 20 new pots bought from markets. They first tested the pots' metal for the presence and amount of lead, then heated the pots and cooked plain rice and khichuri in them, and finally measured the lead in the water and cooked food in the laboratory using specialised methods.

Every pot tested released lead into the cooked food. In new pots used for the first time, up to 305 micrograms of lead per kilogram was found in plain rice and up to 420 micrograms per kilogram in khichuri. By comparison, the US Food and Drug Administration (FDA) limit for lead in food for babies and young children is 10 micrograms per kilogram.

The researchers said that cooking repeatedly in the same pot over time reduces the amount of lead in food, but it never falls below a safe level. Lead was also found in rice cooked in six of the seven old pots — meaning long-used pots can also pass lead into food.

How a pot is cleaned also matters. Scrubbing a new pot with a steel-wool scourer released about five times more lead into food than using it unscoured, and stirring food with a metal spatula likewise increased the amount of lead released.

Taking into account how much rice children in rural Bangladesh eat, the researchers calculated that a child eating rice cooked in such a pot could take in more than five times the FDA's reference level of daily lead intake through food. This figure was not measured directly in children; the researchers estimated it using a calculation model.

Dr Jenna Forsyth, director of Project Unleaded at Stanford University's Human and Planetary Health programme, said the team tested lead levels in both the cookware and the food cooked in it, to understand how an ordinary pot used in everyday cooking can become a route of lead exposure. She added that lead is invisible and has no smell or taste, so a pot that looks perfectly fine can still pass lead into a family's food, and families have no ordinary way of telling which pot is safe.

Dr Jesmin Sultana, an assistant scientist in icddr,b's Environmental Health and WASH division, said families cook rice and khichuri with great care every day and should not have to worry about whether lead is entering that food from the pot itself. Food-safety-tested cookware should be used especially for preparing food for small children, she said, and if such pots are used, scrubbing with steel wool should be avoided and sour or acidic food should not be cooked in them — though such precautions do not make a contaminated pot completely safe.

The researchers say the responsibility for reducing this risk cannot be left to families alone. Bangladesh has several sources of lead exposure, including lead adulteration of turmeric. The Bangladesh Food Safety Authority (BFSA) and the Bangladesh Standards and Testing Institution (BSTI) can play an important role: existing standards and policies need review, scrap metal needs testing, there must be a system to check whether finished pots release lead into food, and small producers need access to safe raw materials and testing.

Dr Md Mahbubur Rahman, a project coordinator in icddr,b's Environmental Health and WASH division, said clear safety standards are needed for lead passing from cookware into food, and called on the Food Safety Authority to take the necessary steps. He also urged BSTI to create and enforce lead-related safety standards for cookware, saying an affordable pot should not have to mean an unsafe pot, and that better production processes and proper oversight can protect families from this preventable risk.

The researchers noted that this was a small-scale laboratory study, and that more research is needed on different types of cookware and everyday cooking habits. The study was conducted with support from Stanford University's King Center on Global Development.