Three Japanese unions, including one for construction workers, requested in a joint action Friday that Canada, the biggest single supplier of asbestos to Japan, stop exporting the carcinogenic mineral, labor officials said.

Representatives of the unions delivered a letter of request to the Canadian Embassy in Tokyo, stating: "60 percent of asbestos used in Japan is imported from Canada. We would like the export promotion policy to be terminated, given that the hazardous nature of white asbestos has been confirmed."

Canada is the third-biggest producer in the world of white asbestos, a type of the mineral known to be relatively less carcinogenic than other types.

The request was made by the All Japan Construction, Transport and General Workers Union, the National Confederation of Trade Unions and the Liaison Conference of Public Promotion of Public Works Related to People's Life.

The embassy told the unions they will refer the matter to Ottawa and promised to offer a reply in writing, according to the union officials.

The move was part of a global action by unions belonging to the Trade Unions International of Building, Woods and Building Materials Industries. Similar requests have also been filed with Canadian diplomatic missions in 12 countries, including Australia and Colombia.

The All Japan Construction, Transport and General Workers Union, which led the action Friday, has 46,900 members. It is affiliated with the two other unions.

Asbestos is a fibrous mineral used in buildings for insulation and as a fire retardant, among other things.