UV Filters

Q: What is a modified one-generation study?
A: The modified one-generation study, or MOG study, measures developmental and reproductive toxicity parameters, and enables the setting of appropriate dose levels for a cancer bioassay through evaluation of target organ toxicity based on chemical exposure that starts during gestation. This gives scientists the power to detect adverse effects where there is a prenatal exposure, but evaluations occur postnatally.

Q: How do NTP's studies on UV filters relate to humans?
A: Results from the NTP MOG study reports on the toxicity of UV filters, 2H4MBP and EHMC, suggest that they do not show endocrine disruption in animal models.

In the 2H4MBP MOG, NTP found uncertain evidence of reproductive toxicity in rats based on a decrease in F2 (offspring) litter size and evidence of developmental toxicity in rats based on postnatal growth retardation.

In the EHMC MOG, NTP found no evidence of reproductive toxicity in rats. NTP found uncertain evidence of developmental toxicity in rats based on lower offspring weights, though they partially recovered by study end.

When 2H4MBP was given to animals through repeated doses for two years, NTP found uncertain evidence of carcinogenic activity in one of the two rodent species tested. These findings do not suggest that UV filters will cause harm if used by humans in a typical application. It is also important to note that sun exposure without application of a sunscreen that blocks the UV rays can damage skin, and sustained exposure is associated with skin cancer in both animals and humans. The Centers for Disease Control and Prevention (CDC) offers tips to protect yourself from UV radiation.

Q: What is the endocrine disruptor screening panel?
A: The Endocrine Disruptor Screening Panel (EDSP) is a series of guideline tests that aim to determine if chemicals and environmental contaminants interact the estrogen, androgen, and thyroid hormone systems.

Q: What are toxicokinetic studies?
A: A toxicokinetic study measures the concentration of the chemical in blood as a function of time. Toxicokinetic studies characterize how much of the chemical gets in and how long it stays in the body.

Q: What is an Absorption, Distribution, Metabolism, & Excretion (ADME) study?
A: This type of study describes in more detail what happens to a chemical in the body in four different stages:

• 1. For a chemical to reach a tissue, it must be absorbed into the bloodstream - often through mucous surfaces like the digestive tract - before being taken up by cells.

• 2. Next, the chemical needs to be carried to the muscle or organ it will act on, most often via the bloodstream through a process known as distribution.

• 3. The chemical then begins to break down through metabolism. As metabolism occurs, the original chemical is converted to new compounds called metabolites.

• 4. Finally, compounds and their metabolites need to be removed from the body by excretion, usually through the urine or in the feces.

Q: There are some who say that UV filters are an endocrine disrupting chemical. Did your studies find this to be true?
A: In our cell-based studies, 2H4MBP at very high doses added to the culture media interacted with the estrogen and androgen receptors but did not result in the estrogen receptor or androgen mediated biological effects. EHMC did not interact with estrogen or androgen receptors or biological effects. Our studies on these two UV filters did not show endocrine disruption in animal models.

In the larger MOG studies, 2H4MBP and EHMC did not induce effects consistent with estrogenic, androgenic, or anti-androgenic activity. Together these data suggest that in cell models at high concentrations, these UV filters can interact with receptors of the endocrine system, however effects were not observed in vivo.

Q: In your Modified One-Generation and two-year chronic toxicity and carcinogenicity studies, why did you give 2H4MBP to animals through food instead of applying it to skin?
A: Our study aimed to mimic continuous exposure of 2H4MBP in the animals. Rodents eat throughout the day and thus had continual exposure, similar to applying and reapplying sunscreen to skin. This method models the amount of UV filters people could be exposed to via repeated application of sunscreens to the skin or by eating food that has touched UV filter-containing plastics.

Q: Who nominated 2H4MBP and EHMC; why?
A: 2H4MBP and EHMC were nominated for study by the National Cancer Institute due to high prevalence of the chemical in commercial products such as sunscreens and cosmetics, and lack of carcinogenicity data.

Q: What’s next for NTP on UV filter research?
A: We are working on a report summarizing cell-based and short-term animal studies conducted on six additional UV filters: avobenzone, ensulizole, homosalate, octocrylene, octylsalicylate, and padimate-O.