A report in last weekend’s Sydney Morning Herald says fishing bans in Sydney Harbour will have to stay in place for decades due to high levels of dioxins.
The Herald report said that despite an expensive clean-up underway at the former Union Carbide site, the original source of the contamination at Homebush Bay, new figures have shown dioxins from the former pesticide factory have washed more than 10 kms up and downstream. The report says the dioxins cover an area too large to be remediated and authorities say the only answer is to wait until sediments cover the contaminated layer, so the poison cannot be absorbed by fish and small invertebrates.
Even though the water quality in the harbour is much improved, the high levels of dioxins in areas where fish feed means the warning not to eat fish caught west of the Harbour Bridge (imposed in 2005), and to eat only 150 grams a month of fish caught east of the bridge, will likely remain for decades. Unfortunately, it seems many fishos are ignoring these warnings. A survey by the Department of Industry published a month ago found that25.3 tonnes of fish were caught and kept by fishers in 2007-08.
The data on dioxin contamination, collected by the NSW Department of Environment, Climate Change and Water in 2008, shows that large tracts of sediments in the harbour are more contaminated with dioxins than Tokyo Bay or New York Harbour.
Department sampling of more than 25 sites highlighted that dioxin levels in the remediation area in Homebush Bay were 610 picograms per gram of sediment compared with 2.3 for a relatively pristine estuarine environment. There were also readings of 350 picograms 10 kilometres up the Parramatta River and significant readings as far east as Rozelle.
The department’s director of specialised regulation, Craig Lamberton, said lifting the ban would be ”a medium- to long-term thing” and that a large-scale clean-up would be technically and financially impractical.
Asked if the ban could last as long as 50 years, Lamberton said: ”I don’t want to predict, but that’s the kind of thing we are talking about. We think it will be decades.”
Dioxins are classified as carcinogens and, as well as cancers, have been linked to birth defects and skin conditions. The exact health effects at lower levels are unclear.
