NEW YORK, July 23 (Xinhua) -- Twenty-five percent of adults in New York City have high mercury levels in their blood from eating fish, according to a survey released by the Department of Health (DOH) on Monday.

    The DOH says the rates are much higher among Asians and the wealthy, who statistically eat the most fish.

    New Yorkers in the highest income bracket averaged mercury levels of 3.6 micrograms per liter, compared to 2.4 micrograms per liter in the lowest income group.

    Asian women had mercury levels of 4.1 micrograms per liter. Among foreign-born Chinese women, 66 percent had mercury levels at or above 5 micrograms per liter, the point at which it must be reported to the state for monitoring.

    Health officials say mercury levels pose little risk to most adults, but they could increase the risk of cognitive delays for children whose mothers had high mercury levels during pregnancy.

    Pregnant women could eat tilapia, herring or whiting up to five times per week because those fish are very low in mercury, based on an adult serving size of 6 ounces, the health department said. But they should not eat Chilean sea bass, swordfish or fresh tuna, which are too high in mercury, the DOH said.

    Officials also note that fish does have health benefits when eaten in moderation.

    The DOH is releasing a new brochure with advice on how pregnant women and children can keep their mercury levels low. Among the tips: don't eat fish caught in New York Harbor, or the Hudson and East Rivers.

    The mercury information came from the city's Health and Nutrition Examination Survey, carried out in 2004.

    The survey, modeled on another carried out by the Centers for Disease Control and Prevention, is the first one of its kind carried out by a city, the DOH said.