Light
Type
|
%Solar radiation reaching earth’s surface
|
Wavelength
(nm)
|
Depth of penetrance
|
Window glass penetrance
|
Erythrogenecity
|
Carcinogenicity
|
Delayed tanning
|
UVC
|
0
|
200-290
|
Epidermis
|
-
|
+++
|
+++
|
-
|
UVB
|
1.7
|
290-320
|
Epidermis – papillary dermis
|
-
|
++
|
++
|
++
|
UVA
|
6.3
|
320-400
|
Papillary – reticular dermis
|
+
|
+
|
+
|
+
|
Visible
|
92
|
400-800
|
Reticular dermis - subcutis
|
+
|
-
|
-
|
+
|
general principles:
| • | shorter wavelengths more prone to scattering |
| • | weaker energy (longer wavelengths) penetrate deeper |
UVC:
| • | not found at earth’s surface (filtered by ozone layer and water drops) |
UVA:
| • | only 1/1000 as effective as UVB at causing erythema |
| • | steep dose response curve |
| • | some suntan parlors use high output UVA radiation |
| • | action spectra for most photosensitizing drugs/chemicals |
melanin:
| • | decreases transmission of all wavelengths |
| 2. | physically absorbs and converts energy to heat |
| 3. | consumes free radicals(?) |
delayed tanning:
immediate tanning:
| • | not creation of new melanin, but photo-oxidation of existing melanin |
| • | due to UVA and visible light not UVB |
| • | (don’t be confused: the erythema of UVB is visible sooner i.e. 2-6 hours, than that of PUVA i.e. 36-48 hours (72-96 hours for more intense erythema) – “erythema” vs. “tanning”) |
|