by Curlan Campbell
- Larger fish, such as tuna, shark, blue marlin, and swordfish, generally contain higher levels of mercury
- Research conducted in 10 Caribbean countries including Grenada
- Revisiting research to assess mercury levels in Grenada communities would require significant funding
It has been 10 years since Dr Martin Forde published a research paper titled “Mercury and Lead Blood Concentrations in Pregnant Women from 10 Caribbean Countries.” This study found that pregnant women in Grenada had the highest mercury levels among the 10 territories surveyed, with an average bioavailable mercury level of 3.13 milligrams per litre. This level is higher than that of the United States (0.75 milligrams per litre) and Canada. Comparative data shows that Jamaica, for example, has a low of 0.83 milligrams per litre. Infant brain and nervous system development can be affected by mercury exposure before and after birth, and excessive exposure can cause birth defects, reduced intelligence, memory and cognitive issues, and motor skill difficulties.
The research was conducted in Antigua and Barbuda, Belize, Bermuda, Dominica, Grenada, Jamaica, Montserrat, St Kitts and Nevis, St Lucia, and St Vincent and the Grenadines, and Dr Forde presented the findings to all departments and Ministries of Health involved in the Caribbean EcoHealth Programme (CEHP) Persistent Organic Pollutants (POPs) study. The study revealed that consuming fish is a significant cause of methylmercury exposure which is absorbed through their gills and the food they ingest from the water. Almost every fish species contains a bit of methylmercury.
This raises the question: why haven’t there been widespread campaigns to communicate these findings? Dr Forde suggested the solution is not as straightforward as it may seem.
Dr Forde, a professor at St George’s University’s Department of Public Health and Preventive Medicine, discussed the dual aspects of fish consumption. He pointed out that while some fish contain methylmercury, a known neurotoxin, they are also rich in essential nutrients that support brain development. These nutrients include polyunsaturated fatty acids, selenium, iodine, and vitamin D. “Fish contains polyunsaturated fatty acids, specifically omega-3s, which are essential for health. Many people resort to fish oil supplements to obtain these omega-3s, which are crucial for the neuronal development of babies. While it’s possible to get omega-3s from other food sources, fish are often considered the best option. However, there is an irony here: the primary source of these necessary nutrients may also carry a risk, as some fish contain high levels of mercury, specifically methylmercury, which can be harmful to development,” he explained.
Dr Forde further explained that to gain a better understanding of this issue, they studied various species of fish and discovered that mercury levels can vary significantly. In general, larger fish tend to accumulate more mercury. Therefore, opting for smaller fish is likely to reduce exposure to mercury while still providing a higher amount of beneficial polyunsaturated fatty acids.
Pregnant women are encouraged by the Grenada Food and Nutrition Council (GFNC) to include seafood, especially fish, in their diet for iodine. On the other hand, breastfeeding women should not have more than 2 portions of oily fish weekly, as suggested. This is due to the presence of mercury in fish, which can have adverse effects on a child’s development.
Dr Forde explained that larger fish, such as tuna, shark, blue marlin, and swordfish, generally contain higher levels of mercury compared to smaller fish species.
A study in Bermuda revealed elevated levels of mercury in different types of fish. Ten years later, Dr Forde evaluated the mercury levels in women and compared them with the findings from the first study. “We observed a noticeable drop in mercury levels over the decade, suggesting that educating consumers — particularly pregnant women — about which fish to consume likely contributed to this decrease.”
Dr Forde expressed interest in conducting a similar research update in Grenada but raised concerns about the high costs involved; blood tests can be expensive, and revisiting the research he initially conducted would require significant funding. However, he noted that since over 10 years have passed, it would be valuable to assess whether there have been any changes in mercury levels among Grenadians. “To my knowledge, there haven’t been any systematic efforts to advise the population on which types of fish are safe to consume. If we discover elevated mercury levels in the community, it would be beneficial for the Ministry of Health to implement measures aimed at reducing these levels,” he said.
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