1 in 4 NYC adults has elevated blood mercury levels

July 23, 2007

A quarter of adult New Yorkers have elevated blood mercury levels, according to survey results released today by the Health Department, and the elevations are closely tied to fish consumption. Asian and higher-income New Yorkers eat more fish, and have higher average mercury levels, than others both locally and nationally. These mercury levels pose little if any health risk for most adults, but may increase the risk of cognitive delays for children whose mothers had very high mercury levels during pregnancy.

Today’s findings are the latest presented from New York City’s Health and Nutrition Examination Survey (NYC-HANES), the first such survey ever conducted by a U.S. city. It’s possible that other cities have similarly high levels, or higher ones, but haven’t yet documented them. Because mercury is a concern for the health of newborns, recommendations on mercury exposure are most important for pregnant and breastfeeding women.

-- Among women 20-49 years old in New York City, the average blood mercury level is 2.64 µg/L (micrograms per liter), three times that of similarly-aged women nationally (0.83 µg/L).

-- Approximately one quarter of New York City women in this age group have a blood mercury level at or above 5 µg/L, the New York State reportable level.

-- People who eat fish three or fewer times each week have, on average, levels of mercury below the reportable level, while average readings exceed the reportable level among those who eat fish four or more times.

-- Higher-income New Yorkers have higher mercury levels; New Yorkers in the highest income bracket average 3.6 µg/L, compared to 2.4 µg/L among the lowest income group.

-- Average blood mercury levels are considerably higher among New York City Asian women (4.1 µg/L); nearly half (45%) have blood mercury levels at or above the State reportable level.

-- Among Asians, foreign-born Chinese women have particularly high levels compared to the rest of New York City. Two thirds (66%) have mercury at or above the reportable level.

-- Foreign-born Chinese New Yorkers eat an average of three fish meals per week, compared to about one among New Yorkers overall. About one quarter of Chinese New Yorkers eat fish five or more times each week, compared to fewer than one in 15 overall.

Health officials emphasized that fish is an important part of a healthy diet, and that moderate fish consumption has many health benefits. “For most people, frequent fish consumption is not a concern,” said Daniel Kass, the Health Department’s Assistant Commissioner for Environmental Surveillance and Policy. “Fish is a good source of protein and heart-healthy fats, and it’s low in calories and unhealthy fats.”

During pregnancy, however, mercury can pass from a mother’s bloodstream to a developing fetus. Small amounts can also pass into breast milk. And exposure to significant amounts of mercury early in life may cause learning problems because the brain is still developing. “No one needs to stop eating fish, but some people may need to change the type and amount they eat,” Kass said. “Young children, breastfeeding mothers, and women who are pregnant or planning pregnancy should eat fish that are lower in mercury and limit fish that are higher in mercury.”

To help educate New Yorkers about which fish is right for them, the Health Department has developed recommendations for pregnant and breastfeeding women and young children. They’re contained in a brochure entitled “Eat Fish, Choose Wisely,” which is available in English, Spanish and Chinese through 311. The brochure provides advice about how to keep eating fish while keeping mercury exposure low:

-- Choose fish lower in mercury.
-- Don’t eat fish that are high in mercury.
-- Eat fewer, or smaller, servings of fish.
-- Choose smaller fish.
-- Eat a variety of fish.

The brochure lists fish by their level of mercury. High-mercury fish include Chilean sea bass, grouper, king mackerel, marlin, orange roughy, shark, swordfish, tilefish, tuna steaks and sushi grade tuna. A typical adult serving size is 4 to 6 ounces (a 4-ounce fish steak or fillet is about the size and thickness of a deck of cards). A child’s serving should be smaller. To estimate serving sizes, read food labels or ask about weight.

People who eat larger portions can avoid excessive mercury by eating fish less often than recommended in the chart. Restaurant servings are often much larger than the recommended serving size.

The Health Department also reminds people about contaminants in fish caught in New York City’s rivers and harbors. “Young adults and women who are pregnant or nursing and young children shouldn’t eat fish caught in the East or Hudson Rivers or in New York Harbor,” said Kass. They may contain harmful contaminants.

Source: New York City Health Department