Sam Judd: What's killing our killer whales?

After a long week educating over 1,000 school students about rubbish in Whangarei last week, I went for a scallop dive out on the heads of the harbour.

Although it was getting dark, I managed to bag 18 of them freediving the popular Smugglers' Cove, in 10-14 metres of water.

Eager for a feed, I shucked my bounty straight after the dive. For the first time in my life, I found plastic - a piece of nylon fishing line - in seafood that I had caught myself.

While I already know that the pollutants which people allow to escape into the ocean are tainting our seafood, this time it really struck a chord with me and spurred me to highlight the results of some shocking research that was conducted right here in Whangarei.

Last year, the award-winning researcher Ingrid Visser made a disheartening discovery in the Whangarei Harbour. One of the orca that she passionately studied washed up dead on the beach after eating stingrays.

The footage of some of Visser's work below was captured by fellow Kiwi Steve Hathaway (an award-winning underwater videographer):

Visser managed to get a sample piece of dead stingray flesh that the orca had consumed and also took a sample from the dead mammal. She sent them away for testing and they both came back positive for high concentrations of flame retardants and polychlorinated biphenyls (PCBs) - man-made pollutants that are likely to have passed into filter feeders (like scallops or mussels), then to the stingrays and up the food chain to the orca.

Chemicals like these can 'bioaccumulate' as they ascend the food chain - getting exponentially worse each step up. This is potentially a reason why the orca washed up dead on our beach.

PCBs are not only endocrine disruptors (which mimic the female hormone oestrogen) but are also known neurotoxins. In humans the exposure to these has lead to delayed development and reduced IQ. Although we cannot measure the IQ of an orca, delays in development have been noted in apex-predators such as polar bears that have been exposed to these chemicals. This means cubs aren't the skilled hunters they need to be and with the impacts of climate change already being felt by the polar bear population, it is making life even tougher for this wonderful creature.

What is of great concern is that PCBs were banned in most industrialised countries in the 1970s, the global production banned in 2004 by the Stockholm Convention on Persistant Organic Pollutants. Yet, they are still wreaking havoc on apex predators.

Their legacy is lasting.

A good sign however, is that a recent study on polar bears around the Norwegian archipelago of Svalbard has noted declines in the levels of PCBs and OH-PCBs (toxins created by the body when PCBs are metabolised) since the bans were put in place. This could be confirmation that global bans on products that are known to impact human and animal health can make a difference.

But I believe that consumer action rather than governing body regulation is more effective in actuating change from manufacturers. Perhaps this could be the path forward for ridding the ecosystem of other known toxins such as styrene and BPA. People are becoming much more aware of what is contained in the products we purchase - it is our right. So anyone out there can use their purchasing power to avoid such chemicals. On a large scale, this will change the way companies produce environmentally harmful products by removing the demand for them.

So next time you're about to buy a bottle of water or a bunch of grapes on a styrene tray that is wrapped in cling-film (a practice I abhor - but that's another story), at least find out what you are buying, seek alternatives that are not full of chemicals and try to make a choice that won't have a long term impact on people and animals.