MBBT and TBPT are the abbreviations for substances used in sunscreens to filter out the ultraviolet component of light and thus prevent sunburn. They are examples of so-called organic UV blockers. MBBT and TBPT convert UV light into heat. They do not occur in nature. Instead, they are always produced by the chemical industry.
How can I come into contact with this material?
If you apply sunscreen to your skin or use cosmetics with UV blockers, they could contain one of the substances MBBT, TBPT, or both. You can check this by looking at the list of ingredients, which is usually printed on the back of the packaging. However, MBBT and TBPT are commercially available under a variety of different (brand) names.
Another possibility of encountering MBBT and TBPT is in bathing areas through washed-off sunscreen in the water. However, since MBBT and TBPT dissolve very poorly in water, they are more likely to remain in the sediment, i.e., the soil of the aquatic environment. MBBT and TBPT have been detected in aquatic sediments and on beaches.
Is there any risk from this material to humans and the environment?
MBBT and TBPT are approved for use in cosmetics by the responsible authorities, both in their bulk form and as nanomaterials. They are used in sun creams and cosmetics with UV protection. In sun creams they are allowed to have a maximum concentration of 10% of the total volume (i.e., 10 ml per 100 ml of cream). MBBT and TBPT are not expected to enter the body during the usual application of sunscreens on the skin, as the skin is a good barrier against these substances. Negative effects of MBBT and TBPT from sunscreens have not been demonstrated to date. On the other hand, MBBT and TBPT protect against skin cancer.
Washed-off MBBTs and TBPTs from sunscreens dissolve only very poorly. Since they are also hardly degraded by natural processes, they remain in the natural environment for a long time. In bathing lakes, organisms living on or in the bottom of the lakeshore could therefore absorb MBBT or TBPT. So far, however, studies have not demonstrated any negative consequences of such uptake.
MBBT and TBPT are so-called organic UV blockers. They convert harmful UV light into harmless heat. So far, there are no studies showing that MBBT or TBPT could be harmful to humans or the environment. However, MBBT and TBPT are poorly biodegradable. Currently, it is still unclear as whether this has consequences for humans and the environment.
By the way
MBBT and TBPT are used as substitutes for the inorganic UV blockers titanium dioxide and zinc oxide. Together with other substances not discussed here, they are responsible for the sun protection factor in sun creams and protect us against skin cancer.