In a controversial new lawsuit brought by two L.A. law firms against certain sunscreen manufacturers for allegedly misleading the public, one charge against the manufacturers is inappropriate use of the phrase “broad-spectrum” UV protection. The accusers say this term falsely implies that the sunscreens provide equal, complete protection against both ultraviolet B (UVB) and ultraviolet A (UVA) rays, fooling people into thinking they can apply sunscreen once and stay outside safely all day, without other sun protection.

Therefore, we think this is the perfect time to explore exactly what "broad spectrum" means, how the expression originated, and how accurate current use of the term may be.

Misinformation or Misunderstanding?

As surely as the word “broad” does not mean “full,” “broad-spectrum” UV protection does not mean “full” or "complete" protection. No single strategy – except permanently staying inside – accomplishes perfect sun protection.

Nonetheless, sunscreen has improved substantially over time. Decades ago, it protected only against UVB, the sun’s short-wave radiation ranging from 290 to 320 nanometers (nm). Research had clearly linked UVB to sunburn and skin cancer. However, exposure to UVA, long-wave radiation between 320 and 400 nm, was considered of little consequence.

Then, UVA was shown to be the primary cause of premature skin aging (photoaging), and to exacerbate UVB's carcinogenic effects. “UVB was considered the primary offender in sun damage and skin cancer until we published studies showing that UVA and UVB combined were more damaging than UVB alone,” says Isaac Willis, MD, professor of dermatology at Morehouse and Emory Universities, who served on The Skin Cancer Foundation’s first Photobiology Committee, a group of experts on the effects of solar UV. “UVA causes pigment darkening (tanning), and people used to think this offered protection, but tanning is really DNA damage.” (Indeed, recent studies show that UVA penetrates the skin deeper than UVB and may actually be more damaging.)

The Advent of Broad Spectrum

Because of such findings, broad-spectrum UV protection was born, as manufacturers added chemicals broadening sunscreen coverage into the UVA range. Currently 16 active ingredients are FDA-approved for sunscreens in the U.S., and several offer UVA protection. However, just how broad UV protection needs to be has remained uncertain, and the FDA has never passed laws clarifying the question. Thus, sunscreens defending against varying UVA ranges claim broad-spectrum UV protection. For example, chemicals called benzophenones were among the first significant UVA absorbers. They primarily absorbed UVB, but extended protection to 340 nm in the UVA range, which many considered broad-spectrum UV protection.

Today, ingredients such as avobenzone (Parsol® 1789), titanium dioxide and zinc oxide have extended UVA protection further. “With these newer additives, sunscreens offer protection across the entire UVA spectrum. Products providing such protection can properly be called ‘broad-spectrum’,” says Warwick L. Morison, MD, professor of dermatology at Johns Hopkins Medical School and current Photobiology Committee chairman. "These ingredients combined with UVB-absorbing chemicals have greatly improved sunscreens." In the near future, he notes, European imports such as the UVA blocker mexoryl should extend protection even further.

A Question of Measurement

Unfortunately, no standard exists in the U.S. to measure UVA protection. It does abroad, but the FDA has never approved one. The standard we have, SPF (sun protection factor), is a holdover from when sunscreens shielded against UVB alone; it only measures UVB protection.

Nonetheless, higher SPF sunscreens do usually offer greater protection against UVA, especially when they contain one or more UVA-targeted chemicals.When The Skin Cancer Foundation developed its Seal of Recommendation for sunscreens, its Photobiology Committee established SPF 15 as the acceptable standard, partly because SPFs under 15 absorbed too little UVA. “SPFs as low as 3 or 4 were once seen as helpful, but we found it took a minimum of 15 for adequate protection,” recalls Dr. Willis. “The PABA (paraminobenzoic acid) derivatives that once formed the base of all sunscreens could not absorb UVA, but esters of PABA (as well as zinc oxide and titanium dioxide) could absorb both UVB and UVA. Broad-spectrum UV protection was born when PABA and esters of PABA were combined, achieving an SPF of at least 15.”

In general, says Dr. Morison, the higher the SPF, the broader protection extends. “No sunscreen blocks 100 percent of UV, but applied properly (1 ounce to all exposed areas 30 minutes before sun exposure, and reapplied every 2 hours), an SPF 15 protects against 93 percent of UV, SPF 30 against 97 percent, and SPF 50 against 98 percent.”

But remember, no matter how good a sunscreen is, some UV reaches the skin. The Foundation considers sunscreen one vital part of a comprehensive sun protection program that includes UV-blocking sunglasses, a wide-brimmed hat, and other sun-protective clothing, as well as shade, especially between 10 a.m. and 4 p.m.