Ultraviolet Radiation

ABSTRACT

It is now commonly accepted that exposure to solar ultraviolet radiation in the wavelength range from 280-320 nanometers (UVB) is associated with induction of human non-melanoma skin cancer. While solar UVB radiation probably contributes greatly to any individual's total exposure to UVB radiation, it is not the only source. The proposal is made that the overall incidence of non-melanoma skin cancer is related to the total ~ exposure and that a part of this exposure may come from artificial light sources. Supporting this hypothesis is an analysis of experimental results (Krell and Jacobson, The Relationship Between Sunlight-Induced and Fluorescent Lamp Radiation-Induced Toxicity and Mutagenicity in L517&Y 'louse Lymphoma Cells, 7th Annual Meeting of the American Society for Photobiology, June 24-28, 1979) indicating that exposure to UVB radiation in a room brightly lighted with the bare fluorescent tubes tested may be about 0.04 times as effective a mutagen as exposure to sunlight. Fluorescent lamps, high intensity mercury vapor discharge lamps, sunlamps and xenon arc lamps are among the artificial sources of UVB radiation to which an individual may be exposed. That UVB radiation from such sources can influence mutagenesis in calls in ~ulture is taken as support for a role of such exposure in the overall non-melanoma skin cancer rate.

ULTRAVIOLET RADIATION EXPOSURE IS OBVIOUSLY ASSOCIATED WITH OUTDOOR OCCUPATIONS. HOW LARGE IS SUCH EXPOSURE, HOWEVER, WHEN COMPARED TO THAT RECEIVED BY AN OFFICE WORKER? THREE EXAMPLES ARE CONSIDERED:

EXAMPLE 1 - AN OFFICE WORKER IS EXPOSED TO EMISSIONS FROM BARE FLUORESCENT LAMPS EACH DAY, THE WORKER SPENDS ONE-HALF HOUR IN SUNLIGHT EACH WORKDAY AT LUNCH. ON THE WEEKEND, THE WORKER IS EXPOSED TO SUNLIGHT FOUR HOURS SPREAD OUT OVER EACH WEEKEND DAY.

EXAMPLE2 - THE SAME OFFICE WORKER NOW USES A SUN LAMP EACH WORKDAY IN ADDITION TO THE EXPOSURES ABOVE.

EXAMPLE 3 - AN OUTDOOR WORKER IS EXPOSED TO SUNLIGHT EACH WORKDAY AND GETS EXPOSED ON WEEKENDS JUST LIKE THE OFFICE WORKER.

THE IRRADIANCE OF SOURCES MENTIONED ABOVE IS SHOWN IN TABLE I:

TABLE 1

	`IRRADIANCE`	`JEM`
`BARE FLUORESCENT LAMPS`	`2.75 W/M2`	`1 x 10-3`
`SUN (NOON)`	`302 W/M2`	`2.2 x 10-4`
`SUN (DAILY AVERAGE)`	`184 W/M2`	`2.2 x 10-4`
`SUNLAMP`	`19.18 W/M2`	`2.7 x 10-2`

THE RESULTS OF COMBINING SOURCE IRRADIANCE WITH THESE EXPOSURE SCENARIOS ARE SHOWN IN TABLE II.

`SCENARIO`	`EXPOSURES`	`TOTAL ENERGY`
`# 1`	`8 HOURS BARE FLUORESCENT LAMP` `EXPOSURE/DAY/5 DAYS`	`3.96 X 10⁵`
	`1/2 HOUR SUNLIGHT/DAY/5 DAYS`	`2.72 X 10⁶`
	`4 HOURS SUNLIGHT/DAY/2 DAYS`	`5.30 X 10⁶`
		`8.42 X 106 J/M²`

`#2`	`8 HOURS BARE FLUORESCENT LAMP` `EXPOSURE/DAY/5 DAYS`	`3.96 X 10⁵`
	`1/2 HOUR SUNLIGHT/DAY/5 DAYS`	`2.72 X 10⁶`
	`10 MINUTES SUNLAMP/5 DAYS`	`1.14 X 10⁴`
	`4 HOURS SUNLIGHT/DAY/2 DAYS`	`5.30 X 10⁶`
		`8.43 X 10⁶J/M²`

`#3`	`8 HOURS SUNLIGHT/DAY/5 DAYS`	`2.65 X 10⁷`
	`4 HOURS SUNLIGHT/DAY/2 DAYS`	`5.30 X 10⁶`
		`3.18 X 10⁷ J/M²`

FROM THIS DATA, IT IS EASILY CONCLUDED THAT SUNLIGHT IS THE OVERWHELMING SOURCE OF UV EXPOSURE.

WE HAVE AN ADDITIONAL PIECE OF DATA, HOWEVER, WHICH INFLUENCES THAT CONCLUSION. WE KNOW THE JEM VALUE FOR EACH OF THE SOURCES IN THE SCENARIO(FROM TABLE I). WHEN WE WEIGHT THE TOTAL EXPOSURE BY THE MUTAGENIC EFFECTIVENESS, THE VALUES IN TABLE III ARE OBTAINED.

TABLE III

`SCENARIO`	`IRRADIANCE / JEM`	`TOTAL EFFECT`	`SOURCE`
`#1`	`3.95 x 10⁵ x 10^-3 =`	`396`	`FLUORESCENT LAMP`
	`2.72 x 10⁶ x 2.2 x 10^-4 =`	`598`	`SUNLIGHT`
	`5.3 x 10⁶ x 2.2 x 10^-4 =`	`1166`	`SUNLIGHT`
		`2160`	`TOTAL`

`#2`	`3.96 x 10⁵ x 10^{-3 =}`	`396`	`FLUORESCENT LAMP`
	`2.72 x 10⁶ x 2.2 x 10^{-4 =}`	`598`	`SUNLIGHT`
	`5.30 x 10⁶ x 2.2 x 10^{-4 =}`	`1166`	`SUNLIGHT`
	`1.14 x 10⁴ x 2.7 x 10^{-2 =}`	`308`	`SUNLAMP`
		`2468`	`TOTAL`

`#3`	`2.72 x 10⁷ x 2.2 x 10^{-4 =}`	`5980`	`SUNLIGHT`
	`5.30 x 10⁶ x 2.2 x 10^{-4 =}`	`1166`	`SUNLIGHT`
		`7146`	`TOTAL`

THIS ANALYSIS SHOWS THAT FLUORESCENT LAMP UV AND SUNLAMP UV CAN CONTRIBUTE SIGNIFICANTLY TO THE TOTAL DETRIMENT ENTAILED IN THESE SCENARIOS.

THE TOXIC AND MUTAGENIC ACTION OF COOL WHITE FLUORESCENT LAMPS ON L5178Y MOUSE LYMPHOMA CELLS CAN BE ELIMINTATED BY FILTRATION OF WAVELENGTHS SHORTER THAN 388 NW WITH A COMMON PLASTIC DIFFUSER.

JACOBSON, E.D. ET AL. "TOXICITY AND 19UTAGENICITY OF RADIATION FROM FLUORESCENT LAMPS AND A SUNLAMP IN L5178Y MOUSE LYMPHOMA CELLS." MUTATION RESEARCH 51: 61-75 (1978).

CHEMICALS FOUND IN OR USED AS MEDICATIONS, COSMETICS, OR FOOD ADDITIVES CAN ACT TO SENSITIZE INDIVIDUALS TO ULTRAVIOLET RADIATION. SUCH SENSITIZATION HAS BEEN SHOWN TO INCLUDE PHOTOCARCINOGENICITY MEDIATED BY PSORALEN DERIVATIVES AND RADIATION FROM A UVA FLUORESCENT LAMP.

STERN, R.S. ET AL. "RISK OF CUTANEOUS CARCINOMA IN PATIENTS TREATED WITH ORAL NETHOXSALEN PHOTOCHEMOTHERAPY FOR PSORIASIS." NEW ENGLAND J. OF MEDICINE 809-813 (1979).

STERN, R.S. ET AL. "SKIN CARCINOMA IN PATIENTS WITH PSORIASIS TREATED WITH TOPICAL TAR AND ARTIFICIAL ULTRAVIOLET RADIATION." LANCET: 732-735, APRIL 5 (1980).

RISK FACTORS SUCH AS TOTAL EXPOSURE, COMPLEXION, AGE, AND THE ABILITY TO TAN INFLUENCE THE CHANCE OF DEVELOPING NON-MELANOMA SKIN CANCER FROM SOLAR ULTRAVIOLET RADIATION. EXPOSURE HAS THE LARGEST INFLUENCE ON THE RELATIVE RISK.

VITALIANO, P.P. AND F. URBACH. "THE RELATIVE IMPORTANCE OF RISK FACTORS IN NONMELANOMA CARCINOMA." ARCH. DERMATOL. 116: 454-456 (1980).