By Eulalee Thompson, Staff Reporter 
EATING FISH is a double-edged sword. On the one hand, nutritionists say that fish is a rich source of proteins, fats, vitamins, calcium and iodine but, on the other hand, fish is turning out to be a formidable dietary source of the heavy metal, mercury.
The 'culprit' fish to beware of are shark, swordfish, King Mackerel or Tilefish. The general public may be able to withstand the high levels of methylmercury that these fish harbour in their tissues but the World Health Organisation (WHO) advises that the health risks for some vulnerable groups such as pregnant women, women planning to become pregnant, nursing mothers and young children may be great.
Various international agencies have set safe limits for mercury in food in their populations. In the latest advisory on mercury in fish issued in March, the U.S. Food and Drug Administration (FDA) says persons in these vulnerable groups are advised not only to avoid high-risk fish but to eat only two fish meals (up to 12 ounces) per week using a variety of fish and shellfish with lower levels of mercury such as shrimp, canned tuna, salmon, pollock and catfish. The FDA states that albacore ('white') tuna has more mercury than canned light tuna, therefore only six ounces or less of this type of tuna should be eaten each week.
Mercury serves no known function in human biology. It's highly toxic nature makes it a menace to the central nervous system and the kidneys. Young children and foetus are particularly vulnerable to brain damage and their developing nervous system could be affected when exposed to mercury. More research is being carried out on the use of mercury in dentistry as an amalgam with other metals.
Large fish such as swordfish and sharks, generally found with higher tissue content of mercury, local scientists say, are not caught in Jamaican waters for consumption. Furthermore, samples of lobster, conch and freshwater fish in Jamaica have been found, by local scientists at the International Centre for Environmental and Nuclear Sciences (ICENS), located at the University of the West Indies (Mona), to be well within the limit for mercury set by the European Union (EU).
Dr. Cedric Lazarus, senior veterinary scientist at the Ministry of Agriculture, also indicated that the Ministry's laboratory does regular residue testing in food (in particular freshwater fish and conch) for three heavy metals cadmium, mercury and lead. About 260 fish samples and 130 conch samples are tested each year for cadmium and lead and about 50 fish and conch samples are tested yearly for mercury, with each test costing between $2,000 and $3,000.
"We are not finding any levels above the international coded standard for mercury in fish," Dr. Lazarus said.
Most countries follow a maximum reserve level (MRL) of 0.3 ppm (parts per milligram) for mercury (recently reduced from 0.5 ppm). The Ministry is,
however, testing only locally-grown fish and not the imported ones mercury as mentioned before accumulates in mainly large fish such as tuna, mackerel and salmon.
While the fish samples are showing acceptable mercury levels, ICENS research on mercury in soil have found that world mean values for mercury in soil are considerably lower than those found in Jamaican soils, especially in parts of Manchester. Information on the availability of mercury in soil to the food chain was not ascertained but Jamaican values for mercury content in livers and kidneys at autopsy were slightly higher than similar samples, identified by ICENS, in other countries such as Sweden.
ICENS has been conducting ongoing research on potentially harmful elements, including mercury, in the Jamaican environment. They have found mercury levels to be variable, depending on the soil type. High levels of mercury have been identified in organic-rich soils (for example, areas of morass soils such as the Georges Plain and Negril Great Morass). Parts of Manchester with higher levels of mercury have also been found to have high concentrations of several elements including cadmium and Zinc.
How do you feel about eating fish now?
Please send your comments to eulalee.thompson@gleanerjm.com.
