Broad-Spectrum Sunscreens Block UVA and UVB

NEW YORK--Sunscreens represent the first line of defense againstskin damage from the sun, and broad-spectrum products offer thebest protection, Madhukar A. Pathak, MB, PhD, said at a mediaconference sponsored by the Skin Cancer Foundation.

Commonly available products are very effective at preventing theacute effects of ultraviolet B (UVB) radiation, but many productsoffer no protection against UVA light, said Dr. Pathak, seniorassociate in dermatology, Harvard Medical School, and chairmanof the Foundation's Photobiology Committee.

UVB radiation (wavelengths from 290 nm to 320 nm) causes sunburn,tanning, photoaging, and skin cancer induction, while UVA radiation(wavelengths of 320 nm to 400 nm) is associated with the immediatetanning reaction, photoaging, and tumor promotion.

The currently available products (SPF 15 or less) do an excellentjob of preventing sunburn when used properly, but they are unsatisfactoryin preventing tanning, he said. In addition, although sunscreensprovide good protection from the DNA damage caused by low dosesof UVB, it is not yet known how effective they are in preventingDNA damage at high exposure dose levels.

Current sunscreens do only a fair to good job against the chroniceffects of high-dose UVA and UVB radiation, he said. They willameliorate but not necessarily prevent photoaging, sun-relatedimmunosuppression, and non-melanoma skin cancer.

Possible new sunscreen strategies that might provide better protectioninclude the use of antioxidants, free radical quenchers, melanin,and sunscreen-enriched liposomes, he noted, but these are allin the future.

Dr. Pathak said that the "bottom line" for sunscreenstrength is SPF 15. Any sunscreen with a lower SPF does not providesufficient protection. However, he recommends the use of productswith an SPF of 30, because they also provide partial, if not total,protection from UVA radiation.

He urged the use of sunscreens that protect against both UVA andUVB, although these are not as widely known as are those thatprotect only against UVB. He advised consumers to look on thepackage for the term "broad spectrum," for claims ofUVA protection, or for ingredients that are known to provide atleast some UVA protection.

These ingredients include avobenzone (Parsol 1789), oxybenzone,dioxyben-zone, sulisobenzone, menthyl anthranilate, zinc oxide,and microionized titanium dioxide. "Zinc oxide and titaniumdioxide when used at a 4% to 25% concentration are very effectiveagainst UVA," he said. "They are nonsensitizing, goodfor children, and good for long-term use."

Dr. Pathak stressed that the protection of children is a top priority.To that end, the Skin Cancer Foundation is creating a sun awarenessprogram to start in kindergarten.

He added that the attitude and behavior of adolescents and youngadults toward the sun must be modified, and suggested that sunawareness programs be established at recreational areas, resorts,sports stadiums, and other sites of outdoor activities and events.

For those young people who insist on acquiring a bronze look,Dr. Pathak said that this can be done artificially with formulationscontaining DHA (dihydroxyacetone). People who use these so-calledsunless tanners should be aware that sunscreens are still necessaryfor outdoor activities. He said that some companies have improvedtheir artificial tanning products by including chemical sunscreensagainst both UVA and UVB light in their DHA formulations.

A Sensible ABC Approach to Safe Outdoor Enjoyment

Avoid excessive sun exposure between 10:00 AM and 4:00 PM.

Block out the sun's rays; use broad-brimmed hats, umbrellas, long-sleeveclothing. Blue, red, and yellow fabrics are more protective thanwhite, and synthetic nylon and polyester are more protective thancotton; wet fabrics provide little or no protection.

Cover-up with a broad-spectrum sunscreen when outdoors (SPF 15-30).Reapply every 2 hours or more often if swimming or perspiringheavily.

Do not indulge in prolonged sunbathing or outdoor activities;any longer than 2½ hours per day puts an individual at riskfor skin cancer.

Educate children, adolescents, and people under age 25 about thedangers of excessive sun exposure without photoprotection.

From a presentation by Madhukar Pathak, MB, PhD, for the SkinCancer Foundation.