Once again, Austin's environmental leaders and elected officials have produced tangible positive environmental results for the city. This time around, it's Lady Bird Lake that is reaping the rewards of the city's ecological foresight, as levels of a particularly toxic substance in the lake have been reduced by 58 percent. "We were on a trajectory to being unsafe. We have reversed that trend," proclaimed Mayor Lee Leffingwell.

In 2006, Austin became the first jurisdiction in the United States to ban the use of coal-tar sealants, a black liquid sprayed onto parking lots to protect them from the elements. The sealants were banned because they contain extremely high levels of PAHs (Polycyclic Aromatic Hydrocarbons), a group of chemical compounds that can be toxic, carcinogenic, and have been known to cause birth defects in aquatic animals. They can also become concentrated as they accumulate in mussels and clams.

Today, eight years after the ban was first put into effect, a new study shows that average PAH levels in Lady Bird Lake have declined by 58 percent, reversing a 40-year upward trend. The study, conducted by the U.S. Geological Survey, tested for the concentration of PAHs in the water at regular intervals, both before and after the ban was passed.

The problem is that when cars drive on pavement that has been sprayed with a coal-tar sealant, the friction of their wheels break that sealcoat into small particles. Those particles, which contain PAHs, are then washed off the pavement when it rains and carried down storm drains and into waterways. Once in streams or lakes, PAHs have been proven to cause harm, leading to inhibited reproduction and even mortality amongst the invertebrates that often serve as the base of the aquatic food chain. Even worse, the dust from these paved parking lots and even playgrounds has concentrations of PAH's that are in the thousands of parts per million, equivalent to a superfund site. Homes next to parking lots and other treated surfaces can have 125ppm which equates to a 40x increase in cancer risk.

Following Austin's lead, more cities as well as the states of Washington and Minnesota have banned the toxic sealants. Using this good news and solid evidence-based science, a national ban on coal-tar sealants would be a logical next step.  However, Congressman Lloyd Doggett, who has twice introduced such legislation, is not optimistic about national action from this session. He is instead focused on encouraging more local and state governments as well as school districts to adopt bans, and convincing more private businesses to voluntary take actions to stop using them, as a few have already done.

Sealants wear off every five years so there will be no new concentrations of PAH's from the coal-tar sealants here in Austin. There are already effective and affordable alternatives available to seal pavement without the PAH's, so there is no reason to keep using these harmful products anywhere.

By Brandi Clark Burton and Amy Stansbury