A study funded by the Indian Council of Medical Research (ICMR) has for the first time revealed the presence of microplastics in sewage treatment plants (STPs) of Central India.Official records estimate that Indian cities produce about 72,368 million litres of sewage per day (MLD), but only have the operational capacity to treat 39 per cent of this waste.As conventional STPs are not primarily meant to remove microplastics, treated effluent and sludge contain a significant amount of microplastic items, which are ultimately discharged into surface water and on to the soil.Researchers of ICMR–National Institute of Epidemiology (NIE), Indian Institute of Science Education and Research, Bhopal, Academy of Scientific and Innovative Research (AcSIR) investigated the role of seven STPs located in Indore and Bhopal in contributing microplastics to the environment.The study found the presence of microplastics in the outlet of all STPs that were examined, indicating that the discharge of this effluent was the possible source of microplastics.Polyethylene, polypropylene, polyethylene-terephthalate, polyvinylchloride, polyester, polyurethane, polyamide, polystyrene and polyvinyl stearate were the most common types of microplastics. Moreover, the considerable presence of microplastics in the sludge collected from STPs posed a negative impact on the soil and groundwater quality. Hence, the researchers recommended an urgent need to develop and incorporate technologies that can target the removal microplastics in conventional STPs.Besides, the study highlighted effective sludge treatment as a crucial aspect to avoid soil and groundwater contamination. “Bigger plastic items do get the chance of removal in STPs during the primary treatment processes, involving screening and sedimentation, and thus become part of the sludge; while small-sized items flow with the water without getting obstructed and become part of the effluent. According to an estimate, approximately 99 per cent of the plastic particles present in sewage get transferred into the sewage sludge. Thus, sludge generated from the STPs contains considerably higher amounts of microplastic items,” the study.It added that sludge, having microplastic particles, is generally applied on to land, composted or disposed of in dumpsites, further adding to the microplastic pool of the environment.While the discharge of effluent into rivers and lakes contaminates the water resources, application of effluent having microplastics in agricultural activities and gardening, poses negative impact on soil and biotic organisms.