Zimmerman and Anastas on Avoiding Regrettable Chemical Substitutions

The more scientists learn about certain materials and chemicals, the more likely they are to find something bad about them. This, understandably, leads to pressure to replace those chemicals.

But some of these replacements come a little too quickly, before they’re fully vetted for their own potential dangers. Hence, the phrase “regrettable substitutions.” In Science, Julie B. Zimmerman, Associate Professor of Chemical & Environmental Engineering, and Paul T. Anastas, Teresa and H. John Heinz III Professor in the Practice in Forestry and Environmental Studies, wrote about this in their paper "Toward Substitution With No Regrets." Zimmerman also recently spoke on the topic on the radio show The Pulse, on NPR affiliate WHYY (you can hear it here).

Examples of such regrettable substitutions are rife. For instance, there’s Diacetyl, used for flavoring butter, and found to cause lung disease in factory workers. When reports about its dangers became well known, several major food companies replaced it with alphadiketone (2,3-pentanedione. Further tests of this chemical, though, brought with it many of the same hazards as Diacetyl.

A better-known example is bisphenol A (BPA), used in a wide range of products, including plastic water bottles, DVDs, and receipt paper. It’s also used to protect food and beverages from contamination. But widely publicized studies suggested that BPA could cause developmental and reproductive problems in animal and human offspring. So many companies substituted it with the chemical bisphenol S (BPS).

“Yet recent studies have identified toxicological concerns with BPS, suggesting that one hazardous chemical was substituted for another,” the authors write.

So how to avoid these regrettable substitutions? It’s not easy. The chemical alkaline copper quaternary (ACQ) has widely replaced chromated copper arsenate (CCA) in for wood preservation. It’s considered a successful replacement, since it doesn’t have the same cancers risks as ACQ. Even so, there are questions about its environmental impact.

The authors write that a surer way of avoiding risks is by adopting the approach of green chemistry, defined by the EPA as “the design of chemical products and processes that reduce or eliminate the generation of hazardous substances.” Anastas coined the term "green chemistsry" in 1991. But this isn’t easy, either, since examples of such systematic design still aren’t plentiful. For that, we need more resources devoted to the molecular designs of safer chemicals. 

“It is only through this process that we can hope to avoid future regrettable chemical substututions,” Zimmerman and Anastas write.