I didn't just take his word for it, I came home and started doing my research. Now I know that plastic bags, six-pack rings and balloons can all end up in the stomach of marine species like sea turtles, seals and various sea birds and these plastic items will cause death (think about that before the next time you release a helium filled balloon. Sorry to ruin it for you). And I know that noise pollution is a big problem, both from Navy sonar experiments as well as from commercial shipping. What I was surprised to learn was that chemical pollutants in the air and water are both showing up in large concentrations in whales.
I shouldn't be surprised. Whales are at the top of the food chain (like we are) and so all of the pollution that ends up in life forms lower down the food chain concentrates in whales. This is related to the fact that you should limit your intake of certain fish species (like tuna and swordfish) - you need to limit your exposure to the pollution built up in these predatory species. It also has to do with whale biology. The big humpback whales we saw on Stellwagen bank (off the coast of Massachusetts) spend their summers up here gorging on fish, then they migrate south to their breeding and birthing grounds. Food there is much scarcer so they have to live off their layer of blubber for the winter. All those compounds that ended up in the blubber are released into their bloodstream and into mothers' milk.
Still don't see where this ties into gardening? Turns out some of those toxins are organohalines and organochlorines, which are found in herbicides and pesticides. These things do not break down readily so even if you are far from the ocean the compounds you put on your lawn could end up in the milk a newborn whale is fed. The world is a small place and we're all interconnected.