Lead, cadmium used to give colour to coffee mugs could be leaking into you as well
Researchers from Assam University, Silchar, have found a high concentration of lead and cadmium in double distilled water that leached from both old and new glazed, colourful ceramic cups heated in the microwave (convection mode) at 140 degree Celsius for 2.5 minutes.Updated: Jan 07, 2019 23:00 IST
Lead and cadmium that give cups and mugs glaze/lustre and bright colours could be leaking into your tea, coffee or warm malt beverages.
Researchers from Assam University, Silchar, have found a high concentration of lead and cadmium in double distilled water that leached from both old and new glazed, colourful ceramic cups heated in the microwave (convection mode) at 140 degree Celsius for 2.5 minutes.
The study findings by the two-member team are important in view of the widespread use of glazed colourful ceramic cups and mugs as well as microwaves in homes and workspaces to heat food and beverages. Lead and cadmium are the most common metals used in ceramics and glazed pottery.
In the absence of approved standards in India, levels of both these highly toxic and carcinogenic heavy metals breached permissible limits of 0.5mg/l (milligrams per litre) set by the United States Food and Drug Administration (US FDA) for lead and cadmium content in tea cups and ceramic wares.
The average concentration of lead was 15 times more in new cups (7.69mg/l) and six times more in old cups (3.15mg/l) than US FDA norms. Similarly, the average concentration of cadmium at 1.97mg/l in old cups and 1.57mg/l in new cups was three and four times more than the permissible limits.
The Bureau of Indian Standards has permissible limits for both these metals only in enamelware – they are also voluntary – and do not cover ceramics.
“It is surprising that there is no standard for glazes for ceramic ware. Ceramics are made in the small and tiny sector as well, so one has to ensure the glazes or slips available are conforming. Their microwaving is another layer of complexity which can cause releases,” said Ravi Agarwal, director, Toxics Link, environmental non-government organisation. “These standards are certainly needed, and we are lagging behind.”
Researchers said regular consumption of beverages from cheap cups, and especially those with ‘Made in China’ labels – they are cheaper and therefore very popular – can be extremely harmful especially for growing children, pregnant women, or women of child bearing age.
Studies have shown that prolonged exposure to lead is associated with memory loss, prolonged reaction time and reduced ability to comprehend, and decrease in IQ in children. Children could also suffer from behavioural anomalies, lack of concentration and learning disorders. Similarly, cadmium can reduce cognitive development in children, and damage kidneys and the reproductive system.
“Glazed cups with colourful paints are very popular in India. These coats are fired on to ceramics at high temperature, but improper firing often results in loosely adherent glaze, which is readily dissolved by the leaching medium,” said Suchismita Das, principal investigator, and assistant professor at the department of life science and bioinformatics, Assam University.
Das said, “The problem arises when the surfaces of cups are not manufactured under strict quality control. The acidic pH of food as well as temperature at which the food is served also influences the migration of metals from ceramics.”
Although the study results are based on heating cups in a microwave, the findings also apply to beverages prepared on the gas stove since the temperature of boiling water is enough to leach the metal from the cup wall. This prediction, said Das, finds support in a prior Belgian work which showed that temperature of 85 degrees Celsius, which is much lower than the current study temperature, extracted 1.14 mg/L lead from ceramics.
Previous studies have found lead concentration of up to 51 mg/L in leachates from Tunisian ceramic mugs. A 2017 study found that lead in the range of 0.2 to 8.6 micrograms per litre (ug/L) in coffee, and from more than 0.2 to 1.6μg/L in tea exceeding the estimated daily dose of lead of 0.5μg/L permitted by the California Maximum Allowable Dose Level.
Lead and cadmium leaching from ceramics has also been found in room temperature. For instance, a 1997 study showed 25–349 micrograms per litre (0.025-0.349mg/L) cadmium leached into orange juice at room temperature from glazed tea mugs made in India.
The study ‘Leachable lead and cadmium in microwave-heated ceramic cups: possible health hazard to human’ was published in Environmental Science and Pollution Research in November 2018.
First Published: Jan 06, 2019 23:00 IST