Pollution in the Mekong River has pushed the local population of Irrawaddy dolphins to the brink of extinction, according to a new report by WWF. The Mekong River Irrawaddy dolphin population inhabits a 190km stretch of the Mekong River between Cambodia and Laos. Since 2003, the population has suffered 88 deaths of which over 60 per cent were calves under two weeks old. The latest population is estimated between 64 and 76 individuals. Researchers found toxic levels of pesticides such as DDT and environmental contaminants such as PCBs during analysis of the dead dolphin calves. These pollutants may also pose a health risk to human populations living along the Mekong that consume the same fish and water as the dolphins. Rob Shore, WWF-UK freshwater programmes manager, said: "Analysis identified a bacterial disease as the cause of many of the calf deaths. This disease would not be fatal unless the dolphin's immune systems were suppressed, as they were in these cases, by environmental contaminants. "These pollutants are widely distributed in the environment and so the source of this pollution may involve several countries through which the Mekong River flows. WWF is currently investigating the source of the environmental contaminants." The report, Mortality Investigation of the Mekong Irrawaddy River Dolphin in Cambodia, found high levels of mercury were also present in some of the dead dolphins. Mercury, suspected to be from gold mining activities, directly affects the immune system making the animals more susceptible to infectious disease. The Mekong River Irrawaddy dolphin has been listed as critically endangered on the IUCN Red List of Threatened Species since 2004.