A Medical Menace
Photoinitiators are used in a variety of everyday objects—including medical instruments. A new study reveals how exposure to certain types of this chemical may pose a cancer risk.

You tend to visit a medical establishment to receive care or stay healthy—but what if there were an environmental factor present during your appointment that was doing the opposite?

A 2021 study published in the journal Current Research in Toxicology has shown that some chemicals used in medical products and instruments promote estrogen growth, encouraging quickened breast cancer tumor development in mice.

These chemicals, generally known as photoinitiators, are used in a variety of products. According to Photoinitiators Platform, an industry group that is active in the regulation and policymaking regarding the chemicals, the following materials are identified as using photoinitiators: wood furniture and flooring, plastic, metal and paper, fiber optics, electronic components, automotive components, printing inks, display and touch screens, solar batteries and fuel cells, flexible electronics, medical devices and lighting components.

The molecules that make up photoinitiators react when exposed to visible and UV light or radiation, cementing it as a popular chemical for quickly curing painted or other coated products. Through curing these materials, the object is able to be handled for daily use without extreme wear and tear—a vital component for common medical instruments.

Photoinitiators have helped us improve the quality of several commonly used products. But it is time we reconsider whether their benefits outweigh their risks.

Photoinitiators Platform advocates for the continued use of photoinitiators in manufacturing, albeit with up-to-date safety regulations. But this new research is, at the very least, grounds for seeking alternatives in the medical space due to the toxic effects of certain photoinitiators.

The 2021 study builds upon research that authors Dr. Yoichi Kawasaki and Toshiaki Sendo first published in 2014. The initial study found that when an in vitro subject was exposed to a group of six specific photoinitiators—2,2-dimethoxy-2-phenylacetophenone (2,2-DMPAP), 2-ethylhexyl 4-(dimethylamino) benzoate (2-EHDAB), 1-HCHPK, 2-ITX, methyl-2-benzoylbenzoate (MBB) and MTMP)—there was a “significantly increased number of MCF-7 cells, an estrogen-sensitive human breast cancer cell line.”

Furthermore, pretreatment with estrogen receptor antagonists such as clomiphene, tamoxifen or fulvestrant significantly reduced the effect of each photoinitiator.

Other previous studies have shown that three of those six photoinitiators commonly found in plastics and paint mimic an increased estrogen presence in cultured breast cancer cells, fueling tumor growth. Those three photoinitiators are 1-HCHPK, MBB, and MTMP.

Looking at these three specific photoinitiators, Kawasaki and Sendo used an in vivo approach with mice to further study the effects that photoinitiator exposure can have on a living organism. Like previous studies, the two also applied a pretreatment of estrogen receptor antagonist Tam, which is commonly used in breast cancer treatment in humans.

All three photoinitiators continued to promote breast tumor growth in vivo as they had in vitro within 13 weeks. Pretreatment substantially decreased toxic effects of the compounds. “This study extends our previous findings and shows that in addition to promoting the proliferation of breast cancer cells in culture, these photoinitiators also increase the growth of breast tumors in live animals. This implies that they could also potentially hasten disease progression in breast cancer patients,” Kawasaki explained.

The study suggests that the exposure to photoinitiators may not only affect high-risk patients like those with cancer, but it could have the potential to harm even healthy individuals as well. Ultimately, these results highlight the need to seek out alternatives when it comes to the chemicals used in clinical instruments to foster a safer medical environment for all.

“Photoinitiators have helped us improve the quality of several commonly used products. But it is time we reconsider whether their benefits outweigh their risks, and our findings are an important milestone in encouraging this conversation,” said Kawasaki. “We hope that it will prompt more intensive research and stricter regulations on what materials can be adopted for commonly used products, especially those with medical applications.”


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