What is benzophenone?

Benzophenone is widely used in household items such as sunglasses, food packaging, laundry and cleaning products to protect against UV exposure. It can contaminate drinking water and migrate from food packaging to food. Benzophenone is used in some food packaging inks and may migrate to food. Benzophenone occurs naturally in certain foods (such as wine grapes and Muscat grapes) and is added to others as a flavoring agent.
In personal care products, benzophenone is used as a fragrance enhancer or to prevent products such as soaps from losing their fragrance and color under ultraviolet light. Benzophenone derivatives such as BP2 and oxybenzone (BP3) are used in sunscreens. Oxybenzone is used as an ultraviolet absorber and stabilizer, especially in plastics and sunscreens. Benzophenone and oxybenzone are also used in nail polish and lip balm.
The evidence linking benzophenones and different derivatives to endocrine disorders is mixed, with studies suggesting that different benzophenones have different endocrine effects. Some studies have shown that benzophenone has little to no estrogenic activity. However, studies of benzophenone in young female rats have concluded that benzophenone is not an estrogen by itself, but may become an estrogen when it is metabolized by the body into other chemicals (for example, the benzophenone metabolite p-hydroxybenzophenone is an estrogen). Studies in adult rats have shown that metabolized benzophenone can exhibit estrogenic activity. The European Committee on Endocrine Disruption has determined that there is insufficient evidence that benzophenone itself is a human endocrine disruptor.
Some studies have shown that the benzophenone derivative oxybenzone can induce strong antiandrogenic activity in the human breast cancer cell line MDA-kb2. Other studies have shown that oxybenzone has estrogenic activity, as suggested by studies of the estrogen-sensitive MCF-7 breast cancer cell line, but other studies have found lower estrogenic activity. Studies on the estrogenic activity and reproductive effects of oxybenzone have found that oxybenzone can alter the reproductive endpoint of fish. Studies in adult rats found that oxybenzone had no effect on the uterus. Although the evidence on oxybenzone's ability to mimic estrogen is mixed, it can be converted into other forms that exhibit estrogen effects, such as BP8 and 2,4,4 '-trihydroxybenzophenone (THB). BP2, BP8, and THB stimulate the proliferation (growth and proliferation) of MCF-7 cells, which are used to test for estrogen activity.