Raw food sold in most of the markets in Kolkata have dangerous concentrations of lead far above the permissible limit, a study conducted by the Geological Survey of India has found, according to The Indian Express. The report warned that this can permanently damage key human organs.

The study, released on Sunday, revealed that raw food sold on the city’s streets contained an average lead concentration of 23.56 mg/kg, much higher than the threshold value of 2.5mg/kg, The Times of India reported.

According to the study, which was published in the Environmental Science and Pollution Research journal, about 75% of the lead contamination is from atmospheric lead, which is produced by incomplete diesel combustion.

Prolonged exposure to lead can cause permanent damage to the kidneys, liver and haematologic systems, scientists at the Geological Survey of India said, adding that children were more at risk because lead exposure could stall the growth of their brain.

Lead contamination can be reduced by minimising the use of diesel vehicles and by encouraging the city’s residents to use more environment friendly options, the scientists said. Senior scientist Avijit Das, who headed the two-year study, was quoted as saying by The Indian Express that switching to “greener energy sources like LPG/CNG-operated vehicles, battery-operated electric cars and solar cars” could help, along with broadening the metro rail network.