The Health and Welfare Ministry kept secret a report compiled in February that revealed a high concentration of a hormone-disrupting substance has been detected in boxed lunches sold at convenience stores, sources close to the case said Monday.

While withholding the information from the public, the ministry’s Food Chemistry Division secretly released the data to related industries earlier this year, urging them to deal with the problem, the sources said.

The substance — diethyl hexyl phthalate (DEHP) — is believed to damage the reproductive systems of animals. Experiments on animals have shown that DEHP reduces the production of sperm. It is widely used in Japan to make plastics softer, mostly in vinyl chloride.

The report, compiled by the National Institute of Health Sciences and other institutions, suggests the food and packaging of the boxed lunches were contaminated by DEHP residue on the vinyl chloride gloves kitchen staff wore as they cooked and handled the food.

The state-run institution carried out a survey of boxed lunches sold at convenience stores and meals served at cafeterias to examine possible contamination by endocrine disrupters. DEHP was found in all 15 samples of boxed lunches examined by the institution.

In one of the most serious cases of contamination, the level of DEHP in a boxed meal reportedly exceeded the maximum allowable daily intake level set by the European Union — 1.85 mg for an adult weighing 50 kg — the sources said.

According to the sources, the ministry’s Food Chemistry Division, after learning the outline of the report in February, withheld the information from the public and instead contacted representatives of an industry group of vinyl chloride glove makers.

An official of the division told the industry representatives that the DEHP level has substantially increased from an earlier survey, adding that the information was confidential and not to be publicized, the sources said.

He told them that the industry would be in trouble once the data are disclosed and urged the makers to remedy the problem.

The industry representatives told the official that preparations are under way for manufacturing and sales of new DEHP-free products, adding that they will be available from this fall, the sources said.

Kosaku Uchida, chief of the Food Chemistry Division, told Kyodo News that the data in question will be reported to the ministry’s Food Sanitation Investigation Council next week. He also said, however, that the ministry has “not yet decided” whether to publicly release the information.

“I cannot comment on whether the data had been released to the industry in advance,” Uchida said.

In March, the ministry set up an internal committee on the issue, analyzing the data and results of animal tests.

Through discussions of the food sanitation panel, the ministry plans to regulate the use of DEHP-added vinyl chloride gloves in the cooking and packaging of food, and also set a permissible level of daily intake of the substance.

But civic groups working on the issue say the ministry action is too late, since experts have been citing the danger of DEHP contamination in food since last year and food packing firms and glove makers have already begun replacing their products with gloves that do not use DEHP.

More than 300,000 tons of DEHP are produced annually in Japan. The European Union is regulating the use of vinyl chloride containing DEHP for toys for children.

Taisen Iguchi, a professor at Okazaki National Research Institutes, said the ministry should release the data to the public as quickly as possible once tests results are made available.

“The government has frequently withheld such data until administrative measures against the problem have been prepared, saying a hasty disclosure of information could cause unnecessary public anxiety,” he said. “But bureaucrats should establish a method of communication to provide correct information to the public as quickly as possible.”