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https://ntp.niehs.nih.gov/go/uvfilters

UV Filters

Final reports from two NTP Developmental and Reproductive Toxicity (DART) studies are now available (DART-05 and DART-06).

Image of sunscreen products, hat, and sunglasses

Research Overview

Status: Ongoing
Substances: 2-Hydroxy-4-methoxybenzophenone, 2-Ethylhexyl p-Methoxycinnamate

Background Information

Millions of people use sunscreen lotions, creams, and sprays on their skin to prevent sunburn and resulting skin damage. Specific chemicals, known as ultraviolet (UV) filters, are added to sunscreens to absorb or block UV radiation from the sun. UV filters are regularly used in cosmetics for sun protection purposes, and in other products like plastics, toys, or furniture finishes to limit UV degradation. People may be exposed to these chemicals when food comes into contact with plastics that contain UV filters. The UV filter and the body’s breakdown products of the UV filter have been found in urine, indicating that they make their way into the body.

NTP Studies

NTP is working to assess the safety of UV filters through a variety of studies in rodent and in vitro models.

NTP conducted modified one-generation studies in rats to determine if 2-hydroxy-4-methoxybenzophenone (2H4MBP) and 2-ethylhexyl p-methoxycinnamate (EHMC), common UV filters, would adversely affect the animal’s ability to develop and reproduce.

Previously NTP conducted a long-term study on 2-hydroxy-4-methoxybenzophenone (2H4MBP) to test the toxicity and carcinogenicity of chronic exposure to this chemical in rats and mice.

NTP conducted endocrine disruptor panel screening studies to determine if EHMC and 2H4MBP (TR-597) activated the endocrine system. Six other chemicals are also being evaluated for endocrine activity in vitro.

What did the studies find?

See table below for the most up-to-date information on the variety of projects taking place at NTP. For general descriptions of the various studies, please see the FAQs.

Chemical
known by other names
Two-year chronic toxicity studies & endocrine disruptor screening panel studies Modified one- generation study Toxicokinetic studies Absorption, distribution, metabolism, & excretion studies
2-Hydroxy-4-methoxybenzophenone (2H4MBP)
  • Oxybenzone
  • Benzophenone-3
Type of filter: UVB, UVA
Two-year chronic toxicity studies: Completed

Findings:
  • In rats, NTP found uncertain evidence of the toxicity and carcinogenicity of 2H4MBP
  • In mice, they found no evidence
Endocrine disruptor screen panel studies: Completed

Findings:
  • In rat studies, high concentrations of 2H4MBP led to slight effects on estrogen and androgen receptors, but no effect on tissues sensitive to these hormones
Supporting files:
Findings:
  • NTP found uncertain evidence of reproductive toxicity in rats based on a decrease in F2 (offspring) litter size.
  • NTP found evidence of developmental toxicity in rats based on postnatal growth retardation.
  • No effects associated with estrogenic, androgenic, or antiandrogenic activity.
  • Lower body weights in offspring; leading to lower male reproductive organ weights.
Supporting files:
Findings:
  • Concentrations of 2H4MBP metabolites increased with increasing dose
  • No differences between male and female rats
Supporting files:
Mutlu et al. 2017
Findings:
  • 2H4MBP and metabolites were detected in rat plasma after exposure through diet
Supporting files:
Mutlu et al. 2017
2-Ethylhexyl p-Methoxycinnamate (EHMC)
  • Octinoxate
Type of filter: UVB
Two-year chronic toxicity studies: N/A

Endocrine disruptor screen panel studies: Ongoing

Supporting files:
Findings:
  • 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; delays in pubertal development, although lower body weights likely contributed to this effect; and time in estrus was slightly longer in females.
  • No effects associated with estrogenic, androgenic, or antiandrogenic activity.
Supporting files:
Findings:
  • EHMC was absorbed and excreted primarily in urine by 72 h after oral administration to rats and mice
  • Following dermal application, 34-42% was absorbed in rats and 54-62% in mice by 72 h
Supporting files: Fennell et al. 2018
Findings:
  • Two potential reproductive and developmental toxicants were produced by metabolism of EHMC
  • EHMC was cleared from rodent liver cells; less rapidly from human liver cells
Supporting files: Fennell et al. 2018
Octylsalicylate (OSAL)
  • 2-Ethylhexyl salicylate
Type of filter: UVB
Two-year chronic toxicity studies: N/A

Endocrine disruptor screen panel studies: Ongoing
N/A N/A N/A
Octocrylene (OCRY)
  • Octocrilene
  • 2-Propenoic acid, 2-Cyano-3,3-diphenyl-, 2-ethylhexyl ester (9CI)
Type of filter: UVB
Two-year chronic toxicity studies: N/A

Endocrine disruptor screen panel studies: Ongoing
N/A N/A N/A
Avobenzone
  • 1-(4-Methoxyphenyl)-3-(4-tert-butylphenyl)propane-1,3-dione
  • Butylmethoxydibenzoylmethane 4-tert-butyl-4'-methoxydibenzoylmethane
Type of filter: UVB
Two-year chronic toxicity studies: N/A

Endocrine disruptor screen panel studies: Ongoing
N/A N/A N/A
Ensulizole
  • Phenylbenzimidazole sulfonic acid
Type of filter: UVB
Two-year chronic toxicity studies: N/A

Endocrine disruptor screen panel studies: Ongoing
N/A N/A N/A
Homosalate
  • 3,3,5-Trimethylcyclohexyl 2-hydroxybenzoate
Type of filter: UVB
Two-year chronic toxicity studies: N/A

Endocrine disruptor screen panel studies: Ongoing
N/A N/A N/A
Padimate-O
  • 2-Ethylhexyl 4-(dimethylamino)benzoate
  • 2-Ethylhexyl-p-dimethyl-aminobenzoate
  • 2-Ethylhexyl dimethyl PABA
Type of filter: UVB
Two-year chronic toxicity studies: N/A

Endocrine disruptor screen panel studies: Ongoing
N/A N/A N/A

Informational Resources

FAQ

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.

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