A review article published within the journal Science of the Total Environment describes how residual toxins in aquatic animals can impact food safety, food security, and human health.  

Background

The aquatic ecosystem is extremely liable to climate change and other environmental aspects, including residual toxins. Pollution of the marine environment can alter the ocean’s biological, physical, and chemical states, which in turn can severely affect the marine ecosystem and marine wildlife.

The Pacific covers about 28% of the Earth’s surface and is among the many world’s five largest and deepest oceans. From 2003 to 2012, the variety of chemical pollutants entering the Pacific Ocean has increased by 50%. Given its significant impact on food safety, food security, and human health, marine pollution has change into a big public health concern worldwide.

​​​​​​​Review: Residual toxins on aquatic animals within the Pacific areas: Current findings and potential health effects. Image Credit: Wealthy Carey / Shutterstock

Residual toxins within the Pacific Ocean

Based on the origin, aquatic residual toxins might be divided into two categories, including toxins of marine origin and human activity-related toxins. Marine biotoxins produced from dense aggregations of unicellular algae are designated as ‘Harmful Algal Bloom’ (HAB). These biotoxins can accumulate in tunicates, echinoderms, gastropods, fish, and filter-feeding fauna.

Evidence indicates a spatial increase in HABs in recent many years resulting from climate change and anthropogenic activities, especially in Asia-Pacific and North-Pacific regions. Nonetheless, no significant temporal increase in HABs has been documented yet.

Cyanobacteria gain energy via photosynthesis and produce secondary metabolites called cyanotoxins. Essentially the most widely studied cyanotoxins are saxitoxins and microcystins. The frequency of cyanotoxin production by cyanobacteria has increased in lots of regions internationally, including the Pacific Northwest.

Persistent organic pollutants, heavy metals, and microplastics are considered contaminants of emerging concern. These toxic contaminants primarily originated from factories, hospitals and domestic houses, agricultural runoff, and landfill leachates.

Lately, effective interventions reminiscent of the Stockholm Convention have significantly reduced the discharge and subsequent accumulation of persistent organic pollutants in aquatic organisms.

In contrast, a pointy increase in microplastic pollution has been observed in recent times. Evidence indicates that plastic waste accounts for about four-fifths of all marine litter. In response to recent estimates, the discharge of plastics from the mainland to the ocean may reach 12.7 million tons annually.   

Nonbiodegradable and toxic heavy metals enter the aquatic environment mainly through agricultural runoff. These metals, reminiscent of mercury, can easily accumulate in aquatic organisms and transfer to higher trophic levels. Human activities have significantly increased mercury emissions within the environment.

Toxin exposure to aquatic animals within the Pacific Ocean

Microplastics are the main sources of aquatic pollutants affecting over 100 species, starting from plankton to large marine animals. Within the North Pacific Ocean, a higher-than-normal level of polybrominated diphenyl ethers has been detected within the adipose tissue and stomach of seabirds resulting from the consumption of microplastics.

Accumulation of microplastics in small animals living at the underside of the Pacific Ocean has been found to scale back survival rate and species population. Within the Eastern and the Northern Pacific Ocean, many aquatic species have been identified with significantly high levels of microplastics of their digestive system.

The evaluation of various fish species from Indonesia and California fish markets has shown high amounts of plastic debris and man-made fibers in fish. These contaminants are known to affect the endocrine, immune, and reproductive systems of marine fish.

Besides microplastics, toxic chemicals released within the marine environment, reminiscent of polychlorinated biphenyls, are known to affect marine mammals, including dolphins and whales. These toxic chemicals can enter marine animal’s bodies through food, water, or air and cause endocrine and digestive disruptions.     

Impact of residual toxins on human health

In response to recent estimates, per capita fish consumption has increased from 9 kg in 1961 to twenty kg in 2018. Consumption of contaminated aquatic animals, including fish, can significantly affect human health. Residual toxins can disrupt the balance between food requirement and provide by affecting the health and survival of marine animals.

Residual toxins gathered within the human body through ingestion of contaminated seafood may cause quite a lot of health complications, including cognitive impairment and other neurological problems. Paralytic shellfish poisoning attributable to HAB toxins is related to severe health adversities in humans, including cardiovascular shock or respiratory paralysis.    

Cyanotoxins have been found to affect multiple human organs, including the liver, nervous system, skin, and digestive system. Some common symptoms include diarrhea, weakness, muscle tremors, vomiting, pale mucous membranes, abdominal pain, sore throat, and skin irritation. Cyanotoxins are also known to be related to the pathogenesis of primary liver cancer.

Persistent organic pollutants have been found to cause chronic health complications in humans. Excessive exposure to those pollutants may cause congenital disabilities, cardiovascular and metabolic problems, endocrine, reproductive, immune complications, and cancers.

Consumption of heavy metal-contaminated aquatic animals may cause fatal consequences in humans. Mercury is especially concerning amongst heavy metals because it is extremely toxic and might be biomagnified along the food chain. As well as, cadmium and arsenic are harmful to varied physiological systems, including reproductive and nervous systems.

Considering the intense human health consequences of contaminated seafood consumption, various control measures have been applied to guard aquatic animals from exposure to residual toxins. On this context, artificial intelligence and machine learning methods could possibly be effective for predicting pollution sources, detecting pullulation levels, and identifying signs of contamination in seafood products.