A number of tinted plastic bags used in Japanese supermarkets contain high levels of lead, with some of them recording 250 times the safety standard set by the European Union, a study by Kyoto researchers has found.

The researchers believe that the dyes used in the bags contain lead. While most of the bags are burned at waste disposal plants, they warned that residual ashes and bags that do not end up in the plants could pollute the environment.

A group led by Prof Shinichi Sakai at Kyoto University Environment Preservation Center collected 154 different types of colored plastic bags in fiscal 2006 and 196 different types in fiscal 2007 in Kyoto City. They found high levels of lead exceeding EU standard of 100 ppm in 27 and 33 types of bags, respectively.

The highest level detected in the study was 25,000 ppm, and a total of three types of bags contained 10,000 ppm or more. The average level was 310 ppm, according to the group.

They say the trend is seen nationwide and estimate that 84 to 110 tons of lead are used in plastic bags annually in Japan.

Aside from environmental pollution concerns, Sakai said the bags could contaminate the food products put inside.

‘‘There are fears that the bags might have already become a problem in other parts of Asia, and we need to switch the dyes to those that do not contain lead,’’ he said.

He added that municipalities are spending ‘‘a huge amount of money’’ to treat lead and other heavy metals contained in the ashes at waste treatment facilities, so reducing lead used in bags could help them save money.