Joshua Seemu­n­gal

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.

CLICK FOR MORE NEWS