Microplastic pollution has become the most significant marine environmental concern. There has been a surge of information on microplastic contamination in various marine environments worldwide. However, the level of microplastic contamination in marine environments is just begun to understand in Sri Lanka. The present study looked at the microplastic contamination level in the beach sand of Pitipana, Catamaran, and Dūwana beaches along the coast of Negombo, Sri Lanka. Sampling was conducted bi-monthly from March to November in 2017. Beach sand samples were collected from the surface (0-1cm) and subsurface (10-11cm) layers and three regions representing the low-tide, high-tide, and vegetation line of each beach. Sand samples were filtered through 5mm and 1mm sieve-set, and particles greater than 5mm were discarded since they are not considered microplastics. Particles retained in 1mm sieve and the filtrate were collected separately. Microplastics were density separated and categorized into two size classes as 1-5mm and smaller than 1mm. Microplastics in the 1-5mm size-class were categorized as fiber, foam, fragment, and pellet. Microplastics <1mm were subjected to FTIR spectroscopy and identified based on the polymer type. Further, goldstrip sardine, Sardinella gibbosa samples were obtained from the coastal waters of Pitipana and tested for possible microplastic contamination in commercial fishes. Results revealed that the Pitipana beach sand was highly contaminated with 1-5mm category microplastics reporting a mean abundance (±SD) value of 7.2±7.66 particles/m3 by number compared to other sites. The fragment was the dominant type found in Catamaran and Dūwana beaches, while foam was the predominant type in Pitipana beach. However, pellets were not recorded in any of the sites sampled. Polyvinyl chloride (PVC) was the major polymer type recorded in Pitipana beach sand, and polyester was dominant in Dūwana and Catamaran beaches. The FTIR spectra revealed the presence of polyethylene and polypropylene in gut contents of Sardinella gibbosa, suggesting contamination of microplastics in planktivorous fish and potential for accumulation along the trophic chain.

The accumulation of Mismanaged Plastic Waste (MPW) in the environment is a global concern. The amount of waste generated by countries is estimated using globally available data layers and/or empirical surveys. Unlike globally available metadata, MPW estimates based on empirical surveys allow for better visualization of amounts, potential pathways, and hotspots. A model study conducted in 2015, based on global metadata, ranked Sri Lanka in fifth position among the world’s worst mismanaged plastic offenders. However, there is significant uncertainty in the source data on waste generation and the parameters used for model prediction, such as plastic usage (5.1 kg per person per day), since Sri Lanka is predominantly a service-based country with limited plastic-based manufacturing industries. The source data for plastic usage has been derived from a very limited study, biased toward waste hotspots that have not been verified. Our empirical data has shown that population density, one of the key parameters used for global ranking, is a weak predictor of debris densities. Therefore, we argue that the given plastic leakage data and the ranking is an error. Therefore, Sri Lanka’s position in the global ranking deserves reconsideration. Further, we propose the need for model predictions that rely on global metadata to be backed by robust and unbiased designed surveys that are based on empirical data and undergo intense baseline data verification to generate more precise predictions on litter quantities.