If you love shellfish harvested from the Sal river, chances are you may have swallowed way too many microplastics (MPs) with every bite of that tasty, fried mussel.
According to a joint study conducted by researchers at the Goa-based National Institute of Oceanography and Academy of Scientific and Innovative Research and the Tamil Nadu-based School of Civil Engineering, Vellore Institute of Technology, the estuary of the Sal river is contaminated by microplastics, the most prominent of which is residue from vehicle tyres from wear and tear on roads.
"The average number of MPs in shellfish found in the present study is 2.6 MPs/g. Accordingly, the estimated annual intake of MPs from shellfish alone per capita for Goa would be 8084.1 particles per year per person. Shellfish therefore poses a possible threat in terms of consumption, as it is a local delicacy and also consumed by the many tourists in the area," the study states.
Water, sediments and biota, which essentially covers all forms of animal and plant lives, are contaminated with microplastics, says the study, the first such research project conducted in the estuaries of the Sal river, a major source of water and fishing in South Goa.
Marine plants, water, as well as samples of shell fish, finfish, clams and oysters were examined as a part of the study.
"Interestingly, MPs found in all the three matrices, water, sediment and biota from the Sal estuary were dominated by fibres (55.3 percent, 76.6 percent and 72.9 percent, respectively), followed by fragments, films and other plastics. The prominent ubiquity of fibres in all three matrices suggests a variety of sources of MPs, most likely including domestic sewage, effluents from industries and laundry," the study says.
"Fragments were the second most abundant micro-debris in water (27 percent) and biota (16.6 percent). They mostly originate from the degradation/weathering of larger plastic pieces such as packaging materials, plastic bottles and other macro-plastic litter, which are often directly discarded into the estuarine environment," it adds.
The study has also brought to light, traces of three major polymers like polyacrylamide, a water-soluble synthetic agent linked to the mining industry, ethylene vinyl alcohol which is commonly used in packaging and polyacetylene, an electrical conductivity agent.
"These could originate from personal care products, textiles and wastewater treatment plants. Notably, no such beads were found in the shellfish and finfish samples," it adds.
Black coloured MPs are most common in the Sal river, the study says.
"The proportion of black coloured plastics (43.9% and 38.1%) were abundant in water and sediments, respectively, followed by green (16%) in water whereas blue in sediments (29.0%). The black MPs mainly might have come into the environment due to abrasion of tires on the road surfaces as regular wear and tear," the study also states.
The objective of the study was to understand and analyse the abundance of MPs in the estuarine environment and examine how the MPs find their way into seafood "through which humans may also be exposed".