Most face masks claiming to cut exposure to viruses by 95 percent or more fall short of the mark, prompting the government to issue directives to suppliers.
The National Consumer Affairs Center of Japan examined 15 brands of masks sold at convenience stores and mass retailers in Tokyo and Kanagawa Prefecture between August and October, of which 11 underperformed.
Their packaging claimed they cut exposure to viruses by 99 percent or meet the standards of surgical masks that block viruses at a rate of 95 percent. But only three of the 15 brands cut exposure to viruses by 95 percent or more.
Six brands cut exposure to viruses between 80 percent and 95 percent, and two brands were 60 percent to 80 percent effective. Four of the 11 did not even achieve a reduction of 50 percent.
Demand for masks is growing amid the spread of swine flu and the Consumer Affairs Agency fears such claims could mislead consumers.
Although there are no regulations on posting product information in selling the masks, the agency notified the Health, Labor and Welfare Ministry, which oversees the sanitary product industry, to deal with the issue.
The center received 80 complaints over the mask last year but the number jumped to about 600 in the first half of this year alone.