Soleman, a local battery trader, said there are more than 500 shops in the city that buy expired batteries and collect lead to sell it again to battery factories.
Kamruzzaman Sarkar, a chemist of the Department of Environment, blamed the lack of monitoring for the situation.
He said the lack of policy on the management of expired batteries means that they are treated like any other waste.
Gallons of acid from these batteries are dumped into drains while the lead is sold to retail buyers. The batteries are melted in high temperature.
Md Anisur Rahman, conservancy officer of Khulna City Corporation, said they are monitoring the situation and would take legal steps against battery businesses that are polluting the environment.
Kamruzzaman said lead and acid from the rejected batteries are eventually entering the food chain and the human body, causing serious health issues.
Prof Dilip Dutta, who teaches environmental science at Khulna University, said lead and sulphuric acid from expired batteries are more dangerous to human health than the environment.
“If these chemicals enter the human body, they can damage the brain, and sometimes people can become handicap. These chemicals may also cause cancer,” he said.