Submitted by William H Harriss

The April 9–10, 2021, eruption of La Soufrière volcano in St. Vincent produced a massive ash plume carried eastward by prevailing winds, blanketing much of Barbados with heavy ash deposits. The ash fall was nationwide, though the northern region of Barbados was the most severely affected in the first days. Reports described Barbados being “submerged in ashfall” and experiencing massive debris on roads, homes, and public spaces.

The ash layer was thick enough to reduce visibility and cause respiratory problems, especially for those with allergies or pre-existing lung conditions. Winds carried the ash quickly — within 90 minutes to 3 hours of the eruption, and in some cases as little as 19 minutes for dust to reach Barbados. The ash blanketed agricultural land, contaminating crops, livestock, and water sources. And right there is a possible problem that will affect the Bajan people for years to come.

While exact precise tonnage or depth measurements of ash per square kilometre are not provided in the available reports, the description of “massive ashfall,” “thick layer,” and “nationwide” coverage indicates that the ash deposits were substantial and widespread, with the northern areas receiving the heaviest load. The event required a large-scale cleanup and had significant environmental, health, and economic impacts on Barbados.

It is a well-known scientific fact that volcanic ash is a wonderful additive for the soil and acts as a mineral fertiliser. But the unsung problem with it is that it is also rich in heavy metals. When crops, particularly root crops, are grown in soil that contains it, the heavy metals transfer to those vegetables. Then, when people eat those crops, they become poisoned by heavy metal intake. The heavy metals are carcinogenic and are known to cause cancer in humans.

Exposure to heavy metals like lead, mercury, arsenic, cadmium, arsenic and thallium can cause a wide range of diseases affecting the brain, nervous system, kidneys, liver, cardiovascular system, and skin, type two diabetes, as well as cancer.

When heavy metals accumulate in the kidneys, they cause tubulointerstitial nephritis and other forms of chronic kidney injury. Currently, kidney disease is a significant and growing public health issue in Barbados, with both chronic kidney disease (CKD) and end-stage renal disease (ESRD) affecting a notable portion of the population.

Heavy metals are also linked to several types of Diabetes. In 2024, 13.2% of adults aged 20–79 in Barbados had diabetes, with 34,400 people affected. The proportion of undiagnosed diabetes is significant — about 23.8% of people with diabetes in Barbados are undiagnosed

For the last ten years, the beaches and waters in Barbados have been invaded by what people recognise as seaweed called sargassum, which is in fact a type of algae.

In 2023 Science Direct wrote an important report about sargassum in Barbados. https://www.sciencedirect.com/science/article/pii/S0025326X23004964

Tropical Atlantic blooms of pelagic Sargassum spp. present major socioeconomic and ecological challenges for Caribbean and West African nations. Valorisation of sargassum provides an opportunity to ameliorate some of the damage to national economies; however, the active uptake of arsenic by pelagic sargassum creates significant barriers to its use. When defining valorisation pathways, it is important to understand arsenic speciation in pelagic sargassum, given the different levels of toxicity associated with different arsenic species. In this study, we assess the temporal variability of total arsenic and inorganic arsenic in pelagic sargassum arriving in Barbados; and test whether arsenic concentrations are linked to oceanic sub-origins. Results indicate that inorganic arsenic, the most toxic form, represents a consistent and substantial percentage of the total arsenic present in pelagic sargassum, and that variability in arsenic concentration does not appear to be driven by sample months, years or oceanic sub-origins/transport pathways.

Sargassum is also a great fertiliser and can make plants grow fast and strong, but just like volcanic ash, it is loaded with carcinogenic heavy metals. Sargassum contains between 20,000 and 40,000 times more arsenic than is found naturally in seawater. Arsenic, lead, and mercury are highly toxic to humans.

Heavy metals are environmental pollutants. They can accumulate in soil, seawater, drinking water, and air and enter the food chain. Humans are exposed to these agents through oral, dermal and nasal routes.

A 2018 study by the University of the West Indies found trace amounts of lead and mercury in some parts of the island’s groundwater. While these heavy metals are present in low concentrations, they pose long-term health risks, especially in vulnerable populations. For instance, mercury levels were found to be as high as 0.001 mg/L, exceeding the WHO’s recommended limit of 0.0006 mg/L in certain areas.
https://olympianwatertesting.com/alarming-water-quality-concerns-in-barbados/

But where are their current reports on what is happening today. Things have changed for the worst sine the SVG volcano eruption in 2021, and the sargassum disposal in land fill sites, and its use by farmers.

After entering the human body, heavy metals may reach various organs and cause health issues. Because the metals are cumulative, long-term exposure increases the risk of cancers associated with the lungs, breast, skin, GI tract, and prostate.
https://www.bing.com/search?pglt=299&q=heavy+metals+are+cumulative

Toxic heavy metals trigger oxidative stress by increasing free radical production and disrupting redox homeostasis. Free radicals damage DNA bases, and if not repaired by the DNA repair mechanism, these alterations can lead to mutations. These mutations increase the risk of cancer by inducing inflammatory molecules and disrupting the cell cycle mediators. Excess metals can also disrupt cellular defences and modulate signalling pathways, leading to uncontrolled cell proliferation. Some metals, including Co, Ni, and Cd, may inhibit the DNA binding of p53 family core domains and abolish the transactivation of several promoters (e.g., BAX), thereby affecting the cell cycle. Low levels of As impede the p53 activation. Certain heavy metals, including Pb, Cr, and Ni, induce inflammation by upregulating the pro-inflammatory cytokines like TNF-α, IL-1β, and IL-6 through the MAPK-dependent pathway. Heavy metals can activate the NF-κB pathway, leading to the upregulation of inflammatory molecules and the onset of carcinogenesis. They also modulate the p21-dependent MAPK pathways.
https://www.bing.com/search?q=Toxic+heavy+metals+trigger+oxidative+stress+by+increasing+free+radical+production

Barbados has a prevalent case rate of about 1,081 per 100,000 people, placing it among the higher rates in the Caribbean and globally for Alzheimers and dementia. It is well known that heavy metals cause mental illness. Lead, mercury, arsenic, cadmium, and manganese all cross the blood-brain barrier, disrupt neurotransmitter systems, trigger neuroinflammation, and alter gene expression in ways that produce measurable psychiatric symptoms. The evidence is stronger for some metals than others, but the overall picture is clear enough that researchers now consider toxic metal exposure a genuine, underappreciated biological driver of mental illness.

Farmers in Barbados have been putting sargassum on their land, which is poisoning the water table, and fruit and vegetables grown in the soil it is added to. If that soil is also volcanic ash-rich, then it is getting a double dose of heavy metal, from the volcanic ash and the sargassum.

Next year, the amount of arriving sargassum is forecast to be double that of this year. There is so much of it that there is no real way to deal with it other than a tiny 2%. In Barbados, some is being taken to make biogas products. It would be good and transparent public information to know how they are removing the heavy metals before using the sargassum, if at all. If the heavy metals are not pre-removed, they could well be poisoning the air and atmosphere with heavy metals when the gas is used in cooking or combustion engines. Very close watch by Bajan government departments needs to be kept on this process.

Some industrial sargassum users who make things with it claim to remove heavy metals with bacteria during mulching; others say they wash it out, which is impossible. One claims that heavy metals are being removed through mulching and microbial biomass treatment. The truth is that arsenic is the greatest contaminant in sargassum, and certain introduced microbes can convert it by oxidation from arsenite to arsenate. That makes it less toxic, but still toxic to humans. The toxicity of arsenate is significant but generally considered lower than that of arsenite. Arsenite, by contrast, is more toxic due to its ability to interact more readily with cellular components.

To understand the small difference in toxicity, if “arsonate” and “arsonite” refer to arsenic-containing compounds — for example, arsenate (AsO₄³⁻) and arsenite (AsO₃³⁻) — then the oxidation state of arsenic in arsenate is +5, and in arsenite it is +3. Oxidation would mean increasing the oxidation state, so the proposed bacteria could oxidise arsenite to arsenate under the right conditions. However, the reverse — reducing arsenate to arsenite — is a reduction, not oxidation. These microbes are not a reducing agent; they are an oxidising agent, so they would not convert arsenate back to arsenite. Instead, it would tend to oxidise arsenite further if present.

But the problem is not fully solved, or at all, because nature kicks in and about 40% of the vegetable types that take up arsenate reconvert it to arsenite. Therefore, the whole process is a waste of time except as a fraud on the minds of people to make them believe the product made from sargassum is safe.

Soil poisoning is well known to scientists, and you can be sure people in authority somewhere in Barbados are already informed of the dangers to the population from heavy metal poisoning.

It is most unfortunate that such knowledge and information are often kept from the public by governments to protect the farming and agricultural industries from collapse.

It may be just possible that in Barbados no one has ever thought about the possibilities of heavy metal poisoning from volcanic ash, volcanic clinker and debris. Like they are still ignoring the massive poisoning dangers that sargassum brings with it. Fish eat sargassum, and their flesh then becomes poisoned with heavy metals. We eat the fish and adopt that same heavy metal the fish carried to our dinner table.

So, between eating local produce, eating local fish, swimming in local sargassum-laden seawater, and walking and handling sargassum, the Bajan people may be subjected to mental inflictions, kidney failure, and cancer, more so than places where none of those factors come into play.

I hope the sargassum collected every day from the beaches not being disposed of on the land or in landfill sites without the heavy metals being removed. Because if it is not removed, eventually it will poison the drinking water supply. It may even end up in the islands excellent rum. If it is being pre-removed, please tell us how. I really do not believe it is possible with such large amounts involved.

Few realise heavy metal poisoning is an emergency and needs to be treated as such. Soil, near-water-caught fish, and produce should be sent to a university capable of analysing samples to a high degree. Also, analyse the drinking and potable water supply.

Heavy metals in soil is absorbed by plant roots and accumulate in edible parts. All soil in Barbados should be analysed for contamination before planting.

If your farmland or garden is near old buildings (lead paint), industrial sites, busy roads, or areas with historical pesticide use, or has had volcanic ash settled on it or sargassum spread on it. It is important to have the soil tested. Even without those suspicions, it is advisable to have it tested.

Root vegetables are the most susceptible to heavy metal uptake from the soil, including potatoes, sweet potatoes, ground nuts, carrots, and all other root vegetables.

Sugarcane can take up heavy metals such as lead (Pb), cadmium (Cd), arsenic (As), chromium (Cr), nickel (Ni), and mercury (Hg) from contaminated soil, polluted irrigation water, and agricultural chemicals like phosphate fertilisers. The extent of uptake depends on soil composition, pH, organic matter, and farming practices. For example, no-tillage systems and high clay or alkaline soils can increase metal accumulation. The heavy metals can transfer to white sugar and other byproducts.

Barbados is a high-risk area due to past massive ash from recent Vincentian Volcanic activity, and now that sargassum is being used as a soil additive.

Even if soil tests show low content, test vegetables periodically, as heavy metals are cumulative and can accumulate over time and in certain plant species.

Just remember, low heavy metal intake by people over a few years becomes enough to feed a foundry. Heavy metals are cumulative; a little over time becomes a lot, and the human body cannot dispose of them, so the amount inside you may be growing with every meal.

There is a capable Barbados laboratory for heavy metal testing at the Centre for Commercial Analytical Services (CCAS). Located at the University of the West Indies Cave Hill Campus, CCAS. They offer advanced analytical and testing services in agriculture, food processing, and the hospitality sector. Their scope includes environmental, agricultural, and food-related testing, which can cover heavy metal analysis in food products. It is important to insist on the most reliable testing methods for detecting and quantifying heavy metals in plants and vegetables, and that is Inductively Coupled Plasma Mass Spectrometry (ICP-MS), supported by proper sample preparation and extraction protocols.

Just an afterthought. It really is unfortunate that many island governments and their government departments cannot be relied upon to carry out heavy metal soil tests and give a true report on the heavy metal findings. They try to hide bad news that may bring panic or damage to the tourist industry. It all becomes a state secret. It may be that initially an NGO can be found to take on this urgent testing task and give detailed and truthful reports.