Confronting heavy metal contamination in Trinidad and Tobago

by Tamara Nowrang (BSc., NEBOSH Certified)

One of the key targets under SDG 6: ‘Clean Water and Sanitation’ is to “improve water quality by reducing pollution, eliminating dumping, and minimizing release of hazardous chemicals and materials…” by the year 2030. As such, more questions have been raised in recent years regarding the ecological and human health concerns associated with the increased release of heavy metals in our natural environments. When researching this from a Caribbean perspective, the information showed that this is a key sustainability issue that must be confronted.

For those of you who may not be familiar with the term, ‘heavy metals’ are elements that have a high atomic weight and a density which is at least five times greater than that of water. While, heavy metals may occur naturally in the earth’s crust, the prevalence of these materials has significantly increased in the natural environment due to anthropogenic activities. This is because industrial, domestic, agricultural, and medical practices have fueled the rate at which these substances are released.

Based on the CERCLA Priority List of Hazardous Substances that was issued by the Agency for Toxic Substances and Disease Registry (ATSDR), the top three hazardous substances are the heavy metals known as arsenic, lead, and mercury in that order. Cadmium, another heavy metal, also finished at number seven on the priority list. With these heavy metals being used and released at an all time high, questions have been raised regarding the ecological and human health concerns associated with this increase.

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Bioaccumulation & Biomagnification

The key concern with regards to the increased release of heavy metals into our natural environment comes from the fact that heavy metals are associated with a process known as bioaccumulation. Due to this process, heavy metals can easily enter the bodies of marine organisms for example fish, either through their gills, digestive track, or body surface. The accumulation of these heavy metals can affect their individual growth rates, physiological functions, mortality levels and reproduction patterns.

Bioaccumulation can then lead to another process known as biomagnification wherein there is an increase in the concentration of the heavy metal as it moves up trophic levels in the food chain. Thus, if a fish ingests heavy metals and it bioaccumulates in its body, the predatory species which consumes it would be subject to higher concentrations of heavy metals.

As a result of this, heavy metals can have negative health effects on humans who consume marine organisms that have been contaminated by heavy metals. The heavy metals which were listed as being the top three hazardous substances (arsenic, lead, and mercury) and all known to be directly linked to severe health implications on humans, as follows:

• Arsenic: Acute arsenic exposure leads to the destruction of blood vessels and gastrointestinal tissues while also having potential effects on the brain and the heart. Chronic arsenic exposure, also known as arsenicosis, has been linked to several cancers including colon, skin, and lung cancer.
• Lead: Acute lead toxicity symptoms include headaches, loss of appetite, abdominal pain, and fatigue while chronic lead toxicity can cause birth defects, mental retardation, paralysis, damage to kidney and brain and even death.
• Mercury: This is known to cause damage to the brain and kidneys of humans, while also increasing the risk of pregnant women giving birth to offspring that display reduced motor neuron function, memory loss and speech impediments. Methylmercury, the form that is usually present in marine organisms, is also highly carcinogenic and has been shown to cause chromosomal problems.

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Is this a cause for concern in Trinidad and Tobago?

A study conducted by Wendy Norville of the Institute of Marine Affairs states that Trinidad’s Gulf of Paria receives high levels of heavy metal input from urban runoff, agricultural and industrial activity, and sewage and domestic wastes. Furthermore, the UNEP (United Nations Environmental Programme) states that the coastal waters near the oil installations in Trinidad and Tobago, show high amounts of heavy metals in surrounding sediments. Given this evidence, it can be suggested that heavy metal contamination in the marine environment in Trinidad and Tobago is quite high.

To further raise concern, researchers at the University of the West Indies, St Augustine conducted a study on the mercury, arsenic, cadmium, and lead concentrations in species of commercial sharks found in Trinidad and Tobago. Results from their study provided sufficient evidence which suggested that heavy metal contamination in fish is indeed a cause for concern for the country. Among the results gathered, the researchers found that lead and cadmium concentrations were generally highest in the two species analysed.

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What can be done to mitigate the problem?

If this article has piqued your interest around heavy metals and the potential impacts that heavy metal contamination can have on human and environmental health, you must be wondering that we can do to minimize negative impacts. To tackle this issue, more focus should be placed on water quality testing and monitoring to ensure that the heavy metal concentrations in local water bodies are in compliance with the standards provided in the Water Pollution Rules of Trinidad and Tobago. There can also be the potential amendment of local standards (based on further research) and/or creation and enforcement of stricter rules regarding the disposal of waste into local bodies of water.

If you agree that more people need to be aware of heavy metal contamination, please share this blog.

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