joshua.seemungal@guardian.co.tt
Stretching more than 12,000 acres across the Caroni River Basin, the Caroni Swamp is the largest mangrove swamp in Trinidad and Tobago. Known for its natural beauty, the swamp is the home of the country’s national bird, the Scarlet Ibis, and hundreds of other plant and animal species.
However, the 230 square miles of Caroni River Basin also accommodates an extensive array of residential, industrial and agricultural activities. The interaction between the natural environment and the rapid rate of urbanisation and industrialisation seen over the past few decades is a parasitic one.
Pollution and chemical contamination from industrial, agricultural and residential activities are threatening flora, fauna and by extension, human life.
Present in the Caroni River and Swamp are toxic environmental pollutants called heavy metals.
According to the United Nations Environment Programme (UNEP), heavy metals may occur naturally and are essential to life, but can become toxic when accumulated in organisms.
Anthropogenic sources of heavy metals, according to UNEP, include oil refineries, mining, industrial production, pesticides, chemical industries, petrochemical plants, untreated sewage, smelters and vehicular emissions.
According to the British Medical Bulletin, heavy metal toxicity can affect central nervous functioning, leading to mental disorders.
Toxic levels of heavy metals, it stated, can damage vital organs and cause cancers.
In 2011, a team of local and foreign researchers, led by Dr Azad Mohammed of the University of the West Indies’ St Augustine Campus, tested catfish tissue from different sites along the Caroni River.
They tested catfish because the fish tend to be sediment dwellers and absorb sediments in their tissue and gills. They found that the tissue contained seven heavy metals above the tolerable limits set out by the International Atomic Energy Agency (IAEA).
These high levels of heavy metals meant that if the fish were consumed, they were potentially hazardous to human health.
The average concentration of aluminium detected in the fish was 2,300 micrograms per gram dry weight–166 times the International Atomic Energy Agency’s limit of 13.8 micrograms per gram dry weight.
The average concentration of chromium was 4.1 micrograms per gram dry weight–five times the IAEA’s limit of 0.73 micrograms per gram dry weight.
Copper was six times the tolerable limit, iron was 13 times the limit, mercury and nickel were double the limits, while lead and zinc were seven times their limits.
According to the United Nations Environment Programme, cadmium is toxic to humans and can cause pulmonary irritation, kidney disease, bone weakness and possibly lung, prostate, and kidney cancer.
High levels of mercury, according to the UNEP, may harm heart, kidney, lung and immune health, brain functioning and may affect the nervous systems of young children and babies.
Ingesting toxic amounts of zinc and copper in the short term may cause vomiting, stomach cramps or nausea.
Long term effects of consuming zinc include lung, kidney, heart, gonad and immune system damage, while the long-term effects of consuming copper include diarrhoea, headaches and kidney damage.
Professor of Tropical Island Ecology John Agard was part of Dr Azad Mohammed’s research team that detected the high levels of heavy metals in catfish in the Caroni River.
“We have some old, general information that this may be an issue, but it hasn’t been redone or retested recently to find out if the matter has been resolved,” he said.
“Our thinking was that since the Sea Lots Dump was close by and the Sea Lots dump is in a wetland, there is water up to the surface, so it is easy for things to leach…Really and truly, there’s no control over what people dump into that dump.”
He said that in more developed countries, there are controls on what can be dumped at landfills and dumps, leading to increased protection of the environment.
Domestic, industrial and agricultural activities leading to the release of pollutants
Marine scientist and UWI lecturer Dr La Daana Kanhai has also studied the presence of heavy metals and chemical contaminants in the Caroni River Basin.
In 2014, she led a local team of researchers in publishing the study “Metals in sediments and mangrove oysters from the Caroni Swamp, Trinidad.”
A year later, in 2015, she led another team in publishing another study called “polycyclic aromatic hydrocarbons (PAHs) in Crassostrea rhizophorae (mangrove oysters) and Cathorops spixii (catfish) from the Caroni Swamp, Trinidad, West Indies.”
Dr Kanhai said when examining the Caroni Swamp and Caroni River, it should not be done in isolation but in the broader context of the Caroni River Basin.
In her research, her team examined multiple sites throughout the basin, testing sediments, oysters and catfish.
The team wanted to see whether there were chemical contaminants absorbed into the sediments and if the oysters and catfish were also accumulating contaminants.
“Yeah, they were. We did find heavy metals in the sediments. So when we compared those guideline levels to international standards, we found that they were between low to moderate,” she said.
“The reason we chose oysters and the reason we chose catfish is these are things humans consume, and so it means to say that if these organisms then have chemical contaminants, there’s the potential for the transfer to occur to humans.”
Dr Kanhai’s team also looked at polycyclic aromatic hydrocarbons, which like heavy metals, are carcinogenic–cancer-causing.
“The petrogenic is the easiest to understand because you think of oil spills and that sort of thing but then you have the pyrolytic sources. So the process of pyrolysis has to occur and that could be associated with vehicular exhaust emissions as well…And we did find these compounds in catfish. We did find them associated with the sediments,” Dr Kanhai said.
According to the marine scientist, domestic, industrial and agricultural activities are leading to the release of pollutants into the Caroni basin.
The UWI lecturer said pollutants are being transported by rivers, allowing them to move from point A to B to C.
She believes the country requires a cultural shift in its view towards pollution of all types.
“Everything is connected and it means to say that you know we have a kind of out of sight, out of mind kind of thinking. So we think that if I get rid of my waste, I don’t need to think about it, but at the end of the day, that waste is going somewhere,” she said.
