While the 1970s are better known for leisure suits and (in my opinion) great music, they were also a bit of a golden age for environmental regulation. The 1970s brought us the Clean Air Act and the Clean Water Act, and in 1976 Gerald Ford signed the Toxic Substances Control Act (TSCA) into law. While the Clean Water and Clean Air Acts have yielded great health and environmental benefits, TSCA has been far less successful. And now, almost 40 years later, Congress is finally considering an update.
The goals of TSCA were to improve public health by (i) assessing and regulating new chemicals, (ii) creating regulations for chemicals which posed health, safety, and environmental risks, and (iii) regulating the distribution of chemicals. However, the goals of TSCA began to be compromised from the very beginning. When it was passed in 1976, 62,000 chemicals currently in use at the time were grandfathered as being “generally safe” and constituted the first version of a list called the TSCA inventory. This decision was made partly due to political considerations and partly to the daunting prospect of performing toxicity tests on all of the chemicals in use at the time. Once the inventory was established, all chemicals either produced in or imported into the United States were required to be on the list.
Under TSCA, in order for a new chemical to be added to the inventory, the manufacturer or importer must submit a pre-manufacturing notice (PMN) to the Environmental Protection Agency (EPA). The data requirements for a PMN are rather limited. While the manufacturer must list the chemical’s formula and structure (a point to which we will return later), no safety or toxicity data are required. In order to regulate, or perhaps even ban the proposed new chemical, instead the burden shifts to the Food and Drug Administration (FDA) to show that it poses “unreasonable risk to human health or the environment.” Since the FDA does not have the resources to perform its own toxicity tests and has only 90 days after the manufacturer submits the PMN to respond, it should not surprise you that essentially 100% of PMNs are approved.
From 1976 to 2015, the TSCA inventory has grown to 84,000 chemicals. During this time period, only five chemicals have been banned by the FDA. These include chlorofluorocarbons, which are responsible for the hole in the ozone layer, and dioxins, polychlorinated biphenyls (PCBs), asbestos, and hexavalent chromium, all known to cause cancer. (Hexavalent chromium was the chemical involved in the Erin Brockovich story.) Unfortunately, the ban on asbestos was partially overturned in 1991 because a federal court found the EPA “failed to show that it had evaluated the cost-benefit impact of the ban.” This ruling further eroded the already limited effectiveness of TSCA.
Of the 22,000 new chemicals added to the TSCA inventory since 1976, only 200 have undergone toxicity testing. The resulting lack of data causes confusion and concerns when incidents occur. For example, last year when methylcyclohexanemethanol (MCHM) was spilled into the Elk River in West Virginia, there was a public outcry over the lack of safety and toxicity information and officials struggled to provide guidance to concerned citizens. As a result, people were frightened and unclear when or if they could start to drink their tap water again. Certainly a nation with our resources can do better than this.
Congress is currently considering too many changes and updates to TSCA for me to cover here. In my opinion, the most significant proposed change is that manufacturers will have to “perform and present a safety evaluation” as part of the PMN, shifting the burden back to the manufacturers to prove that their product are safe. However, the question of what safety testing is required and how it should be performed remains open. This question interests me and was my motivation for writing this column.
There are two primary methods used for evaluating the toxicity of chemicals. The traditional approach is animal testing, which involves applying the chemical to the skin or eyes, injecting it into the blood stream and/or feeding it to mice, rabbits, pigs or other animals. It’s a rather brutal regime. While this sort of cruelty seems, to me at least, to be justifiable if you are seeking a cure for cancer, I certainly hope that we could avoid these techniques if a company, for example, wants to produce a new type of hydraulic fluid for car brakes. I should also point out that animal testing is not always accurate in predicting the toxic effect of a substance on humans.
The other approach to evaluating the potential toxicity of a chemical is computer modeling based on the structure of a molecule. When the mass media addresses this type of approach, it tends to do so with skepticism or derision and implies that shortcuts in evaluating safety are being taken. Computer modeling deserves more respect than this. Let me explain why.
As I reviewed previously in Everything Comes from Oil, Everything, petroleum is the primary raw material for almost everything that you might consider to be a “chemical.” Further, since petroleum is comprised of organic chemicals – those with carbon backbones – the vast majority of the 84,000 chemicals on the TSCA inventory are organic chemicals as well. When you examine the structure of organic chemicals, you find repeating patterns of atoms which scientists refer to as functional groups. Therefore, organic chemicals can be considered to be comprised of different combinations of these functional groups of atoms. The figure below shows some of the most common functional groups:
Considering an organic chemical to be a combination of these functional groups allows its physical and chemical properties to be predicted by computer modeling with great accuracy. Scientists and engineers routinely use this approach to calculate a wide range of properties such as viscosity, boiling point, and chemical reaction rates. Computer modeling based on functional groups can also provide a reliable prediction of toxicity. In addition, computer modeling does not harm any animals.
My recommendation to Congress would be that they provide the funding to allow the EPA to build a computer modeling and database system for toxicity. Not only could this be used to evaluate proposed new chemicals, but can and should also be applied to the entire inventory of 84,000 on the TSCA list. This approach would go a long way towards achieving the goals originally conceived in 1976.
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