We Are Still Poisoning the World

Anthropogenic environmental poisonings, intentional or not.

We have an EPA and long-standing bureaucracies of environmental review, so our environment should be clean, right? Well, rivers may not be burning anymore, but that doesn't mean things are as tidy as they may look. Humanity has proven capable of inventing and selling innumerable chemicals, creating a situation that is far more complex than any kind of precautionary testing or policy making can address. Shocking issues have arisen in recent years that remind us that there is a great deal more to do if we are serious about caring for the biosphere.

6PPD is engineered to react with ozone to become 6PPD-quinone. That protects tire rubber, but kills salmon.

A recent paper showed that the decline of salmon all over the Western US is attributable to a completely unanticipated source. An obscure chemical from automobile and truck tires, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), reacts with ozone to form an incredibly toxic compound, which is killing salmon exposed to roadway runoff. This chemical makes up about 1% of tire formulas, and is meant to react with ozone to protect the rest of the rubber in the tire from degradation. The yearly rate of tire rubber degradation and emission is about a pound per person, leaving a great deal of this poison in the environment. So ... does anyone care? A web search for 6PPD yields very little news, despite this being a clear environmental crisis.

Putting the tire problem in perspective. LC50 is the lethal concentration where half of organisms die.

An even more complicated story came up recently from the southeast of the US, where eagles are dying from a mysterious neurological syndrome. It turns out that an invasive water weed, hydrilla, responds vigorously to agricultural nutrient runoff pollution, and accumulates bromine, of all things. This in turn leads to a bloom of an algal parasite, Aetokthanos hydrillicola which grows on the hydrilla, and produces, as cyanobacteria are wont to do, various toxins, in this case a highly brominated amino acid derivative which causes the eagles' lethal neurological disease.

AETX, a heavily bromimated derivative of the amino acid tryptophan. This is a toxin, causing myelinopathy in eagles after it bio-accumulates in the food chain from ducks and other aquatic browsers that eat the cyanobacterial-infested hydrilla. 

But this is just the tip of the iceberg, based on incredibly painstaking work by chemists newly armed with today's analytical chemistry tools to look at particularly dramatic cases of dead wildlife. What about the lead in firearm ammunition, which litters the countryside and shatters into poisonous shrapnel in its targets? What of the intentional poisonings by farmers and ranchers, that are killing condors in the Andes? What of the landfills and coal ash heaps, and whatever leaches out of them? And what of the mountains of plastic that are increasingly filling the planet's waterways and oceans? They are not just physical nuisances but leach out an uncountable array of obscure chemicals. 

These are slow-motion Chernobyls, which need to be taken seriously and mitigated by a more precautionary approach to new products, a life-cycle approach to collecting and reprocessing existing products, and more investment in cleaning and protecting the environment.

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