When Does Toxic Become Too Toxic?

It might take a degree in environmental chemistry to understand the pollution readings from Pure Castings Co. – and even then, not everyone agrees on what they mean.

The Texas Commission on Environmental Quality's real-time monitoring station has been in operation on the roof at Zavala Elementary since Feb. 19, and the agency has placed the results on its website for public viewing. On a five-tier warning scale, ranging from moderate to hazardous, the PM-2.5 (particles 2.5 micro­meters and smaller) readings have maxed out at "moderate" – which is defined as an hourly average of 20 to 99.9 particles per cubic meter. At its highest, the hourly count was 64.56 particles per cubic meter, but the average so far has been 10.85 particles per cubic meter – below even moderate risk. However, since there is only one station, the readings may rise or fall, depending on which way the wind is blowing, without any backup measurements. Plus, the station only monitors volume on PM-2.5, not individual chemicals.

That's where the TCEQ mobile sampling team comes in. In its three visits to the site in the last year, it has monitored both upwind and downwind of Pure Castings to see what materials the company is adding to the atmosphere and at what levels. The team found an array of potentially toxic and carcinogenic chemicals, including aluminum, nickel, and selenium, but again at allowed levels.

What's "allowed," though, is a complex question. Unlike with ozone, there are no national standards for air toxins, so it's up to individual states to adopt their own. Unsurpris­ingly for anyone who has followed Gov. Rick Perry's constant claims that Texas is the least regulated and most business-friendly state in the nation, Texas has never done so. The only point of reference Neil Carman, clean air director for the Lone Star Chapter of the Sierra Club, can readily use is the Environmental Protection Agency's Risk-Based Concentration Tables. These charts are used to calculate when levels might start to represent a long-term health risk, and Carman discovered that six of the 12 toxic metals found by TCEQ exceed the recommended low-risk concentrations. At its highest, the cadmium measured 24 times the recommended risk-based concentration, while he calculated that cobalt emissions topped out at 178 times the risk-based concentration. And his greatest concern is not the levels of the individual chemicals but what happens when they combine to form what he called "a toxic chemical cocktail."