that covers much of South Asia and the Indian Ocean every year between January and March, and possibly also during earlier and later months, hangs over the Bay of Bengal. It is considered to be a combination of vehicle exhaust, smoke from cooking fires, and industrial discharges. Because of this cloud, satellites attempting to track ocean acidification and other ocean health indicators in the Bay have difficulty obtaining accurate measurements. Pollution and water quality The major transboundary issues relating to pollution and water quality are: sewage-borne pathogens and organic load; solid waste/marine litter; increasing nutrient inputs; oil pollution; persistent organic pollutants (POPs) and persistent toxic substances (PTSs); sedimentation; and heavy metals. The transboundary nature of these issues are: discharge of untreated/partially treated sewage being a common problem. Sewage and organic discharges from the Ganges-Brahmaputra-Meghna River are likely to be transboundary. Plastics and derelict fishing gear can be transported long distances across national boundaries. Around 4 million tonnes of microplastics are estimated to come from India and Bangladesh travelling into Sundurban and subsequently the Bay of Bengal. High nutrient discharges from rivers could intensify largescale hypoxia. Atmospheric transport of nutrients is inherently transboundary. Differences between countries with regard to regulation and enforcement of shipping discharges may drive discharges across boundaries. Tar balls are transported long distances. POPs/PTSs and mercury, including organo-mercury, undergo long-range transport. Sedimentation and most heavy metal contamination tend to be localized and lack a strong transboundary dimension. The main causes of the issues are: increasing coastal population density and urbanization; higher consumption, resulting in more waste generated per person; insufficient funds allocated to waste management; migration of industry into BOBLME countries; and proliferation of small industries. A pertinent issue is the rapid growth of the shrimp culture industry which requires use of antibiotics and chemicals for export-quality food safety but pollutes the Bay of Bengal. Tropical storms and cyclones A tropical storm with rotating winds blowing at speeds of is called a cyclone when they originate over the Bay of Bengal, and called a hurricane in the Atlantic. Between 100,000 and 500,000 residents of Bangladesh were killed because of the 1970 Bhola cyclone. 2021, Very Severe Cyclonic Storm Yaas 2020, Very Severe Cyclonic Storm Nivar 2020, Super Cyclonic Storm Amphan 2019, Very Severe Cyclonic Storm Bulbul 2019, Extremely Severe Cyclonic Storm Fani 2018, Very Severe Cyclonic Storm Gaja 2018, Cyclone Titli 2017, Severe Cyclonic Storm Mora 2017, Cyclone