Residential ambient ultraviolet B and ultraviolet A and incidence of keratinocyte carcinoma in the nationwide US Radiologic Technologists cohort.

BACKGROUND

Few epidemiological studies have distinguished the effects of solar ultraviolet (UV) radiation (UVR) wavelength, including UVB and UVA, on the risk of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) of the skin.

OBJECTIVES

We aimed to evaluate the association between ambient UVB and UVA exposure and the incidence of BCC and SCC.

METHODS

Using data from the nationwide US Radiologic Technologists cohort, satellite-based noontime ambient UVR was obtained based on residential history (< 13, 13-19, 20-39, 40-64, and ≥ 65 years). Incidence rate ratios (IRRs) and 95% confidence intervals (CIs) were estimated for associations between UVB, UVA quintile (Q), and first primary BCC and SCC in mutually adjusted and stratified models, additionally adjusted for sun sensitivity characteristics.

RESULTS

There were 62 595 non-Hispanic White participants aged 22-90 years at baseline (1983-1998). During a median 25.5 years of follow-up, 6339 incident BCCs and 1253 incident SCCs were reported. Annual and summer UVB and UVA were each positively associated with both BCC and SCC risk before mutual adjustment. After adjusting for UVA, summer (but not annual) UVB Q5 vs. Q1 was associated with BCC (IRR 1.41, 95% CI 1.13-1.77) and SCC (IRR 1.69, 95% CI 1.01-2.84). After adjusting for UVB, annual (but not summer) UVA Q5 vs. Q1 was associated with BCC (IRR 1.42, 95% CI 1.13-1.77) and SCC (IRR 1.84, 95% CI 1.10-3.06).

CONCLUSIONS

Both summer UVB and annual UVA were independently associated with higher risks of both BCC and SCC. Our results suggest that cumulative lifetime UVA exposure may be an underappreciated contributor to BCC and SCC risk. If confirmed, these findings may indicate that public health interventions are required to promote avoidance of excessive UVB and UVA exposure among susceptible populations.