Polluted Pearl River Estuary is killing pink dolphins, research finds

Pink dolphin populations are under threat from high concentrations of organic pollutants and heavy metals in the Pearl River Estuary, research backed by Ocean Park's conservation arm has found.

The levels are much higher than those found in the Yangtze and Yellow River estuaries and threaten the marine mammals' immune and reproductive systems, the researchers say.

With funding from the Ocean Park Conservation Foundation, Guangzhou-based Sun Yat-sen University analysed water and tissue samples from the carcasses of stranded Chinese white dolphins, known as pink dolphins.

Detected in the samples were high levels of heavy metals such as mercury, lead and arsenic, persistent organic pollutants and DDT, an organic chloride pesticide banned in most countries including the mainland.

Dolphin campaigners welcomed the research but said the results were nothing new and construction projects were a bigger threat - a notion rejected by the foundation.

"Levels of heavy metals … in the sediment samples from some parts of the estuary waters are much higher than those found in the Yellow River and Yangtze Estuary," Professor Wu Yuping of the university's School of Marine Sciences said.

The professor said the pollutants could affect pink dolphins' immune and reproductive systems and even induce tumours. "Calves and fetuses can also be exposed to the pesticides from the mother's milk and through the umbilical cord."