pesticides pharmaceuticals fish farms feature

A recent study has concluded that the pesticides and pharmaceuticals being used by industrial fish farmers is threatening both swimmers and marine life.

According to the report fish farms are polluting seawater with pesticides and pharmaceuticals, which is contributing to a rise in a genetically engineered species of fish and spreading it’s DNA into the natural wild populations.

In their December 2021 report the trade group Salmon Scotland also concluded that the use of pesticides by the nation’s salmon farms represents a potential risk to swimmers who swim in open ocean waters).

The report’s primary finding is that the use of insecticide products containing azamethiphos (an organophosphate), deltamethrin and hydrogen peroxide to control sea lice in farmed fish contaminates seawater and, thus, threatens swimmers in the areas around the farms.

Beyond Pesticides has reported on pesticide use in aquaculture, and most recently, on developing resistance – in the parasitic lice (Lepeophtheirus salmonis) that endanger both wild and farmed fish populations in the North Atlantic – to some of the chemical treatments used by aquaculturists to combat the parasite.

The intense exploitation of wild fish and other marine creatures for human food (and as an ingredient in animal feeds) has caused, in recent decades, the depletion of fish and seafood stocks across the world.

The aquaculture industry – in which various aquatic species (fish, shellfish and some plants) are bred, raised and harvested in the open ocean – has grown rapidly as a response.

Since the 1960s, the farming of salmon in the Atlantic has grown such that now, 70% of global salmon production is from ocean farming and in the U.S., 90% of salmon sold is farmed.

Other marine food farming industries that dominate U.S. markets include those that produce tilapia, shrimp and shellfish (scallops, mussels, clams and oysters).

Asia is the source of more than 90% of all farmed fish/seafood, with China alone representing roughly 58% of production.

Aquaculture operations generate a host of sustainability issues: seawater pollution from the farms’ waste, pesticides and pharmaceuticals; increased levels of disease in farmed populations; increased use of chemical “controls,” the inevitable resistance to those compounds among pests (such as sea lice); a rise in genetically engineered species and the spread of that DNA into wild populations, among others.

The “escapes” of farmed fish, due to pen damage from harsh local conditions or predators, are common.

This points to yet another problem in this industry: the release of genetically engineered farmed salmon into the wilds of the ocean means that some wild salmon will breed with them and weaken their genetics.

For example, when wild Atlantic salmon breed with escaped farmed salmon, their descendants mature earlier and grow faster than in the wild species, undermining wild populations’ ability to survive and reproduce in their natural habitat.

In 2020 Beyond Pesticides has this to say about the Scottish farmed salmon industry :

“Atlantic salmon . . . are raised in what are, essentially, pens suspended in open sea lochs (arms of the sea that are narrow or partially landlocked) on Scotland’s west coast and Northern Isles. Many of these are in relatively remote areas, so are somewhat ‘hidden’ from public scrutiny.

The fish in these pens live under very crowded conditions, with far greater density than do wild salmon. They are fed processed feed that is usually laced with various pharmaceuticals and/or insecticides used to ward off diseases and pest infestations, such as the sea lice, which tend to break out in such crowded conditions.

The fish also discharge thousands of tons of feces and food waste into the surrounding sea (as well as pesticide and pharmaceutical residues). The food and fecal matter ratchet up the nitrate levels in the nearby marine ecosystem, which has deleterious effects on ocean plants and organisms.

The pesticides and other pharmaceuticals can harm local ecosystems and marine life.”

WCA Environment (WCA), the consultant company that produced the report for Salmon Scotland, indicates that the contamination of marine waters (by the products listed above) happens whether the treatments are done “in situ” at the site of a salmon pen, or on board special treatment boats.

In either case, post-treatment, the water containing the insecticide products is then dumped into the sea.

One might wonder if this is a significant risk, ocean contamination aside – as in, how many folks actually swim in the ocean? It turns out that the U.K.’s Outdoor Swimming Society boasts 100,000 members!

WCA assigned a metric – to each of the three ingredients in the pesticide products (deltamethrin, azamethiphos and hydrogen peroxide) – to represent the relative risk identified.

A risk factor of “1” or below was characterised as “showing no reason for significant concern or action.”

Deltamethrin was determined to be present at levels of negligible concern; azamethiphos was assigned .8, but hydrogen peroxide clocked in at 27.7.

The report concludes that levels of azamethiphos and deltamethrin “in the treatment baths can be considered safe,” but that levels of hydrogen peroxide in salmon cages can be 28 times higher than those considered safe for swimmers.

At high concentrations, hydrogen peroxide is harmful if ingested and toxic if inhaled; it can cause skin burns, eye damage, and irritation of respiratory system membranes.

In light of the report’s sanguine comments about the safety of azamethiphos and deltamethrin, Beyond Pesticides calls attention to these facts:

Deltamethrin is a synthetic pyrethroid insecticide that is an irritant to human tissue, disrupts the human endocrine system, and is toxic to bees and to fish and aquatic organisms.

Azamethiphos, which is permitted for use in salmon aquaculture in Norway, Ireland, Scotland and Chile, is an acetylcholinesterase inhibitor (which action compromises immune and metabolic function), a mutagen (causing genetic mutations) and a neurotoxicant.

Though the first two compounds get a “pass” in this study, Beyond Pesticides points out that this evaluation – as is true for many pesticide evaluations by the U.S. Environmental Protection Agency on this side of the pond – fails to assess risks of exposures to two, or all, of these compounds in combination.

The lack of attention to potential synergistic impacts speaks to the ongoing failures of classic toxicological risk assessment as employed by most regulatory agencies.

According to, the 220+ U.K. salmon farms (operated by eight companies) discharged more than 10.5 million gallons of hydrogen peroxide into sea waters between 2016 and 2021.

The report authors also assert that their assessment of potential risk to swimmers was based on a series of “worst-case assumptions” for the average adult swimmer and that “characterization of dilution and dispersion factors are likely to be required to be taken into account to demonstrate that discharges of hydrogen peroxide are safe for open-water swimmers.”

According to Salmon Scotland maintains that the “‘worst-case’ estimate in [the] report ‘would never occur in real life.’ The pesticide would be dispersed and diluted in the water, it argued, and swimmers kept a ‘safe distance’ from industrial sites and vessels.”

The trade association further asserts that levels of hydrogen peroxide used in the salmon treatments “would fall below the ‘no effect’ level 30 minutes after use and ‘generally’ within 200-–300m. . . . There would be ‘very few, if any’ people who would swim for two hours in Scottish coastal waters.”

The report has garnered significant attention in the context of the consideration by a regional Scottish authority, the Argyll and Bute Council, of a proposal from Mowi, the world’s largest producer of farmed Atlantic salmon, for a new farming operation off the west coast of Scotland’s Isle of Arran.

Advocates have maintained that the “poisons” – pesticides and other chemicals – evacuated (or leaked) into seawater by salmon farms could threaten the health of ocean swimmers, and have demanded regulatory action to reduce or eliminate fish farm chemical pollution.

Scotland’s Coastal Communities Network, a coalition of 23 organisations advocating for the marine environment, insists that pesticides risk swimmers’ health.

Spokesperson for the group, John Aitchison, commented:

“The industry’s own report shows that swimmers will be harmed if they swallow very small amounts of water containing two of the poisons being dumped by fish farms. The risk is especially high for women and children who were not mentioned in the report. No other industry is allowed to dump all its pesticides in the sea.”

Early in the COVID-19 pandemic he was also quoted in the Beyond Pesticides’ 2020 article on the increased use of pesticides on Scottish salmon farms:

“We do not want them to discharge any more pollution. . . . The need to dump even more pollution in the sea during this crisis shows that it must give up its open nets and adopt closed-containment methods to capture its pollution instead, as any other responsible industry would do.”

Fish farms are rough analogs to terrestrial CAFOs – concentrated animal feeding operations. Both crowd too many creatures into too little space; both feed animals with processed food laced with pharmaceuticals and/or insecticides or parasiticides in efforts to “control” the diseases and pest problems that inevitably arise in such living conditions; and both create unnatural concentrations of excreta that move “downstream” to the surrounding environment, whether on land or in oceans and contaminate and impact nearby ecosystems and water quality.

In addition, on land, these operations create fertile conditions for viruses and bacteria to evolve and jump from animal to human populations – potentially launching more human pandemics. This dynamic may be possible from marine farming, as well.

A sensical, precautionary and protective approach would be to raise animals in sufficiently large, more humane and more-natural conditions, such as those required by the U.S. Department of Agriculture’s National Organic Standards.

Such practices would obviate much of the need for the chemical “fixes” operators of these facilities employ.

It is important for the public to know that what Beyond Pesticides wrote in its 2018 coverage of the salmon farming industry is, unfortunately, evergreen: All “Atlantic salmon” sold in the U.S. is farmed.

That is why it often has a slight gray tinge, is oilier and less firm than wild salmon and lacks the rich taste of the wild varieties.

“Organic” salmon – which consumers may see offered in some supermarkets – is certified in accordance with European Union regulations.

But the public should know that, although it may cost roughly the same as genuine wild salmon, it has the same “environmental baggage” as farmed “Atlantic salmon.”

“Organic” fish farming significantly contributes to marine pollution by adding synthetic pesticides and antibiotics to the marine environment, contravening what consumers expect of organic food production systems.

For the public, there are alternatives to participating in this industry.

One is not consuming farmed salmon. Another is purchasing only wild varieties, though that increases pressure on already stressed wild stocks. A third, for those who want to continue eating this fish, is to eat only wild salmon but to reduce the frequency of consumption.

The same approaches can apply to other farmed marine foods, although in the U.S., it is increasingly challenging to find any shrimp or tilapia, for example, that is not farmed.

Given what conventional agriculture, whether marine or terrestrial, has wrought in its impacts on human health, ecosystems and natural resources, concerned consumers now must pay close attention to the provenance of their provisions.

In addition, pressure must be exerted on elected leaders, federal and state regulatory bodies and even the local grocery, to shift food production to systems that don’t cause such degradation, disease and destruction.

And Finally….

The above article was originally written and published by Beyond Pesticides to whom we send our appreciation for their work on this issue.

Editor: Michael W/Rambling in Pen