Voutchkova, AM, TG Osimitz and PT Anastas. 2010. Toward a comprehensive molecular design framework for reduced hazard. Chemical Reviews 110 (10):5845–5882.
Chemists at Yale University are calling on others in their discipline to understand how to design and build safer, less toxic chemicals – right from the start. Their ideas on how to do that are proposed in an article published in Chemical Reviews, which follows an earlier paper that tackles the same topic.
A main target when designing and building unique compounds should be for the compounds to have minimal toxicity yet be commercially useful, according to the paper’s authors. The heart of their suggestions include a broader understanding of toxicity, development of more robust safety tests and use of product labeling programs.
The detailed proposal is a first step toward a new, concerted way of thinking about the design of new commercial chemicals. It focuses on maximizing the desired functions – like cleaning power for detergents – while at the same time minimizing their broader health and environmental effects.
While this seems logical, it is generally not the case. Chemists and engineers tend to focus on building chemicals with novel properties that may help solve current industrial or remediation problems or benefit society in some other way. Unlike pharmaceuticals or pesticides, the potential for new commercial chemicals to cause adverse health effects on people, wildlife and the environment is not always considered upfront.
For example, of the 700-plus commercial chemicals introduced to the market each year, more than 85 percent have no health and safety data. This is because obtaining such data is often too costly and time-consuming.
But, the potential threat of chemicals with unintended human and environmental hazards has become increasingly clear. Phthalates – as plastic additives – are now known to disrupt hormonal balance. Some insecticides – such as the repellent DEET – are severely toxic to the nervous systems of mammals. Other widely-used plasticizers – such as bisphenol A – can interfere with reproductive functions, as increasingly shown from animal research.
These are just a few examples of commercial chemicals whose unintended hazards were discovered long after they were first introduced to the market. To avoid such pitfalls in the future, the authors combed chemistry, biology and toxicology research articles for ways to evaluate chemical safety. They compared how different disciplines test substances meant for products and devised a different approach for chemists to use as they venture to design new commercial compounds.
First, the chemists and engineers who make the compounds need a better understanding of how chemical properties influence toxicity – that is, how they are absorbed and the biological responses to chemical exposure. Many toxicology databases with this information already exist – especially in the area of designing drugs to perform particular functions. Drugs that survive the digestive tract and efficiently enter the blood can be specifically designed. In a similar way, if a commercial chemical is designed to not enter the bloodstream, it will be excreted and thus, much less likely to be toxic to people. Unfortunately, designing a chemical that is not toxic to humans or other animals is vastly more complex than merely ensuring it is excreted quickly, but this is a start.
Second, the right testing tools are needed to scan the creations for toxic effects before product development goes too far. Understanding a chemical’s behavior in a laboratory setting – with test tubes, cells and tissues – can help in understanding its behavior when it interacts with humans and the environment.
In some cases, predictive laboratory tools can forewarn of hazards, but there are still many hurdles to overcome. The available tests and tools are not often applied until the chemical has been produced. In addition, no reliable predictive tools exist for many of the dangerous but subtle hazards – such as endocrine disruption.
An example of an impressive effort to guide development of new chemicals is being carried out by the U.S. Environmental Protection Agency’s Design for the Environment (DfE) program. The program will help industrial scientists consider the environmental and health implications of new chemicals they plan to introduce to the market. Manufacturers who meet the stringent criteria for human and environmental health safety can place a special DfE label on their products, which will also benefit consumers as they strive to make better informed decisions about the products they purchase. Companies that do not meet the criteria may miss out on the marketing advantages of the DfE product label.
Clearly, there is a need for scientists to understand which chemical features are associated with particular hazards and design new chemicals rationally to avoid these elements at the drawing board. Although this approach cannot obliterate the need for detailed health and safety testing, it can significantly improve the odds that a new chemical will not be highly hazardous to people and animals. Bridging the gap between chemistry and toxicology may be a necessary first step to a new way of thinking that could radically reduce chemical hazards.