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Sunscreen and Skin Cancer – the Science

by The Environmental Working Group, Washington DC, USA


The first sunscreens were developed to prevent severe sunburn for military personnel spending long hours under strong and direct sunlight (Maceachern 1964). Today, they are associated with a wide range of purported purposes, from reducing skin aging and direct sun damage to decreasing the risk of skin cancer. Yet expert opinions differ widely on the strength and reliability of scientific evidence that supports these claims (Autier 2009; Draelos 2010).

The power of sunscreen to protect against sunburn is well known; this is the feature of sunscreens identified as the Sun Protection Factor or SPF. Yet, the wide availability of sunscreens has allowed people with light-color skin to stay outdoors longer, often aiming to get a tan or to maximize burn-free time in the sun (Autier 2009; Lautenschlager 2007.


Expert’s recommendations to wear sunscreen are tempered. Skin cancer rates continue to increase in the U.S. and other countries. Studies do not provide evidence that sunscreen protects against the deadliest form of skin cancer, and scientists are not certain about which type of UV radiation, UVA or UVB, is most dangerous and therefore most important for sunscreen to block or absorb. Sobering statistics on skin cancer raise basic questions about sunscreen efficacy:

  • Even though more people use sunscreen than ever before, the incidence of skin cancer in the United States and other countries continues to rise (Aceituno-Madera 2010; Jemal 2008; Osterlind 1992).

  • A number of studies conducted in the 1990s report higher, not lower, incidence of the deadliest form of skin cancer, malignant melanoma, among frequent sunscreen users (Autier 1995; Westerdahl 2000; Wolf 1994).

  • According to the American Cancer Society, malignant melanoma accounts for only 3-4% of all skin cancer cases, but is responsible for 75% of all deaths attributed to the disease each year (ACS 2010) (See side-bar: “The 3 types of skin cancer”)

  • To date, studies show that regular sunscreen use reduces risk for squamous-cell carcinoma (SCC) but not other types of skin cancer. SCC, a slow-growing, treatable cancer, is estimated to account for just 16% of all skin cancers annually.

The 3 Types of Skin Cancer
Skin cancer is the most common cancer in the United States, accounting for nearly half of all cancer cases. One to 2 million people develop skin cancer each year (Bikle 2008; Rogers 2010, ACS 2010). A recent study estimated that the disease is five times more prevalent in the U.S. population than breast or prostate cancers (Stern 2010).

Precise numbers for skin cancer incidence in the U.S. are not known, since non-melanoma skin cancer is usually excluded from cancer registry statistics and, additionally, their incidence varies by the geographical region (Rubin 2005). However, according to a review published by the American Cancer Society, among all the skin cancers 80% are basal-cell carcinoma (BCC), 16% are squamous-cell carcinoma (SCC), and 4% are malignant melanomas, the deadliest form of skin cancer (Greenlee 2001).

Melanoma and Sunscreen: UVA, UVB or Both?
For decades, sunscreens available on the market primarily blocked UVB, the wavelength of ultraviolet radiation that causes sunburns (Draelos 2010). Sunscreen manufacturers and sunscreen users assumed that preventing or delaying sunburn would also protect from other dangerous effects of the sun such as skin cancer.

Today, many experts believe that both UVA and UVB exposure may contribute to melanoma risk (Garland 2003; Godar 2009). Sunscreens produced over the past three decades that blocked UVB but allowed higher UVA exposure may not have been able to provide the necessary cancer protection (Draelos 2010) and may have contributed to risk of melanoma in some populations (Gorham 2007).

Sunlight that reaches the surface of the Earth consists of longer-wavelength UVA (315–400 nm), shorter wavelength UVB (280–315 nm), visible light, and infrared light. UVB constitutes 3-5% of the total UV radiation that gets through the atmosphere, while UVA constitutes 95-97%. UVB, which only penetrates the outer skin layer, is the primary cause of sunburn (erythema or redness) and non-melanoma skin cancer such as squamous cell carcinoma (von Thaler 2010). In contrast, UVA can penetrate deeper into the skin where it causes a different type of DNA damage than does UVB (Cadet 2009).

Even though many sunscreens now include UVA filters, a large number of products available in 2010 still fail to adequately protect sunscreen users from UVA radiation.

A growing body of data points to UVA exposure as a significant factor in melanoma development. But scientists still do not know the relative importance of UVA and UVB in melanoma development (Donawho 1996; Setlow 1993), a knowledge gap that raises the importance of broad-spectrum protection in sunscreens, with filters that absorb both UVA and UVB radiation:

  • “Results from animal models, epidemiological studies, and clinical observations suggest that UVA might play an important role in the pathogenesis of malignant melanoma.” Rünger 1999, Photodermatology, photoimmunology & photomedicine.

  • “Collectively, [current] data suggest a potential role for UVA in the pathogenesis of melanoma.” Wang et al 2001, Journal of the American Academy of Dermatology.

  • “The issue of [melanoma] action spectrum has been a subject of debate, with some groups suggesting that the effect of UVA is predominant in human melanoma with earlier groups having suggested that UVB is the predominant cause of skin cancer in general, although not necessarily melanoma in particular.” Garland et al. 2003, Annals of Epidemiology.

  • “Although sunlight is known to cause melanoma, there has been considerable controversy as to the importance of short (UVB) and long (UVA) ultraviolet (UV) wavelengths in causing melanoma, leading to uncertainty in how best to prevent this cancer. This uncertainty has been compounded by the difficulties in assaying the UVA protection abilities of sunscreens, as compared to widely accepted measures of UVB screening by the sun protection factor (SPF).” Lund & Timmins 2007, Pharmacology and therapeutics.

  • “The [sunscreen’s] ability to prevent sunburns (as measured by SPF) probably does not imply the ability to prevent melanoma or basal cell carcinoma.” Autier 2009, British Journal of Dermatology.
    “The specific contribution of UVB and UVA radiation exposure towards the risk of melanoma is controversial.” von Thaler et al. 2010, Experimental Dermatology.

  • “There is also sufficient evidence of an increased risk of ocular melanoma associated with the use of tanning devices.” International Agency for Research on Cancer (IARC) 2009. “Indoor tanning facilities in general deliver higher relative intensities and higher proportions of UVA compared with solar UV radiation.” IARC 2006.

Why Don’t Scientists Know More About Sunscreen and Skin Cancer?
Three factors preclude drawing definitive conclusions about the effects of sunscreens on skin cancer risk: 1) in parallel with protection from sunburns, application of sunscreens has been also associated with increased sun exposure, including usually unexposed sites such as the trunk (Autier 2000; Dupuy 2005; Stanton 2004); 2) early-generation sunscreens did not provide significant or adequate UVA protection or possibly even sufficient UVB protection (Diffey 2009; Lautenschlager 2007; Osterwalder 2009); 3) sunscreen use in the populations studied may not have been consistent or sufficient to provide the protection from melanoma (Bech-Thomsen 1992; Thieden 2005).

Published studies have examined the correlation between sunscreen use and the development of the three most common forms of skin cancer: basal cell carcinoma, squamous cell carcinoma, and malignant melanoma. In 2000, International Agency for Research on Cancer (IARC) reviewed available data and concluded that:

  • Sunscreen use may decrease the occurrence of squamous cell carcinoma.

  • Sunscreen use has no demonstrated influence on basal cell carcinoma.

  • In intentional sun exposure situations, sunscreen use may increase the risk of melanoma (IARC 2001a; reviewed in Autier 2009).

Studies conducted over the past decade have confirmed that regular sunscreen use lowers the risk of squamous cell carcinoma (Gordon 2009; van der Pols 2006), similar to studies completed in the 1990s (Green 1999). Regular sunscreen application also diminishes the incidence of solar keratosis (also known as actinic keratosis), a type of sun-induced skin changes that may become precursors to squamous cell carcinoma (Naylor 1995; Thompson 1993).


For basal cell carcinoma, follow up studies reported a slight and not-statistically significant decrease in risk associated with sunscreen use (Pandeya 2005; van der Pols 2006). Thus, for this cancer type, data on sunscreen benefits remain negative or equivocal (Hunter 1990; Rosenstein 1999; Rubin 2005).

However, from the public health perspective, physicians are most concerned about malignant melanoma, the deadliest type of skin cancer (Lund 2007; World Health Organization 2006). Sunburns are an important risk factor for melanoma (Leiter 2008). Intermittent, severe sunburns in childhood have been considered to pose the greatest risk, although sunburn during all life periods likely contributes to melanoma development (Autier 1998; Dennis 2008).

State of the evidence: human epidemiology studies of melanoma risk in sunscreen users
Individual studies provide conflicting evidence on the role of sunscreen in melanoma risk. Studies in Sweden, Belgium, France, Germany, Austria, and New York state report an elevated risk of melanoma in sunscreen users (Autier 1998; Beitner 1990; Graham 1985; Westerdahl 2000; Wolf 1998). In contrast, studies in Spain, Brazil and San Francisco, California report decreased risk of melanoma in sunscreen users (Bakos 2002; Espinosa Arranz 1999; Holly 1995; Rodenas 1996).

A 2000 IARC assessment of 15 studies on sunscreen and melanoma revealed conflicting evidence regarding associations between sunscreen and melanoma, with 3 studies showing significantly lower risks on melanoma associated with sunscreen use, 8 studies finding significantly higher risks associated with sunscreen use, and 4 studies reporting no effect (IARC 2001, reviewed in Dennis 2003; Diffey 2009; Gorham 2007; Huncharek 2002).

Some scientists have combined the data from multiple sunscreen studies in what are called “meta-analyses,” which allows them to assess larger or specialized groups of sunscreen users. A meta-analysis of melanoma studies conducted by University of Iowa scientists in 2003, reported a lack of overall association between melanoma risk and sunscreen use (Dennis 2003).


The Iowa researchers suggested that findings of elevated risk in a large group of studies conducted in Europe and U.S. may have been due to confounding effects, such as differences in skin sensitivity to sunlight among people with lighter or darker skin. Sunscreens are more likely to be used by people most at risk of quick sunburn (Diffey 2009; Geller 2002, a group at higher risk for melanoma (Dubin 1986).

In contrast to the conclusion from the Iowa group, a meta-analysis conducted by University of California San Diego scientists in 2007 found a link between the location of the study (high or low latitude from the equator) and the risk of melanoma in relationship to sunscreen use. According to this analysis, in populations living at latitudes below 40o from the equator, the use of sunscreens was associated with a non-significant decreased risk of melanoma, while populations in higher latitudes faced a statistically significant increase in melanoma risk linked with sunscreen use (Gorham 2007).

Skin pigmentation may have been the reason for these latitude effects (Gorham 2007). Studies finding protective effects of sunscreens generally included Mediterranean populations or populations with prevalent Mediterranean ancestry, which have higher degree of constitutive pigmentation. On the other hand, studies conducted in light-skinned populations residing far from the equator (above 40o latitude) generally found a statistically significant 60 percent increase in melanoma risk (Espinosa Arranz 1999; Rodenas 1996).

Experts generally agree that the tendency of sunscreen users to spend more recreational time in direct sunlight and to wear less protective clothing may increase the amount of sun damage that leads to melanoma (Autier 2009; Draelos 2010; Gorham 2007). Additionally, scientists still do not know which wavelengths of sunlight drive melanoma development (Donawho 1996). Thus, historical absence of broad-spectrum UV protection in sunscreen, especially UVA protection, may have contributed to melanoma development or at least to the lack of evidence for a decrease in melanoma risk (Garland 2003; Godar 2009).

With so little known with confidence about sunscreen and skin cancer, it is no wonder that many experts are now recommending clothing and shade, not sunscreen, as primary barriers from sun exposure.  For full details on the report, please click here.



The above information should not be treated as a substitute for the medical advice of your own doctor or any other health care professional.







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