Protecting Workers from Ultraviolet Radiation - icnirp

Protecting Workers from Ultraviolet Radiation
removed (cataract surgery) without implantation of an UVR absorbing lens or if there is no lens
(i.e. aphakia, which is rare), a significant fraction of the incident UVR (290 - 400 nm) may reach
the retina.
The cornea does not adapt to repeated exposures like the skin (by thickening of the stratum
corneum and epidermis). Therefore, the cornea is equally vulnerable day after day to the same
exposure to UVR.
The effects of UVR on the eyelids are equivalent to those described for the skin. For this reason
only adverse effects of UVR to the eye will be considered here.
Since the transparent media of the eye do not have any melanin pigment (as in the skin), there is
no correlation between the UVR sensitivity of the eye and skin type.
3.3.2 Acute effects
An unprotected eye exposed to UVR from the sunlight reflected from light sand or snow during
one day may accumulate a sufficient dose to cause an adverse effect in the cornea of the eye. As
with sunburn of the skin, the symptoms are delayed for several hours. Within six hours such an
exposure gives rise to a gradual transition symptoms form a feeling of itchiness, “sand in the
eye” sensation, increased tearing, to severe pain and photophobia (light sensitivity). This is
caused by an inflammatory reaction in the cornea and conjunctiva known as
photokeratoconjunctivitis, which leads to a swelling and loss of the superficial cells in the cornea
and the conjunctiva. Within 24-48 hrs, the pain decreases and the light sensitivity disappears.
This condition is popularly referred to as “snowblindness” or “welders flash.”
In addition to corneal injury, laboratory studies have demonstrated acute cataract formation from
UVR at wavelengths greater than 310 nm emitted by artificial or laser sources (Pitts et al 1977,
Söderberg et al 2002, Ayala 2005, Hockwin et al 2002). In the unusual situation where the UVR
absorbing lens or lens implant is not present, retinal injury is possible for wavelengths greater
than approximately 300 nm (Zuclich 1989, Ham et al 1982)
3.3.3 Chronic effects
Pterygium is a fibrous ingrowth of the cornea of tissue making the cornea opaque.
Epidemiological data strongly support a correlation between chronic exposure to UVR and
pterygium (Taylor 1992, Taylor 2000, Sliney 2000).
A pingueculum is a non malignant connective tissue tumor in the conjunctiva. Droplet keratitis is
a focal deposition of lipids in the cornea with an adverse effect on transparency. Both of these
conditions have been epidemiologically associated with exposure to UVR (Lim et al 1998,
Taylor 1992).
Development of cataract, a clouding of the lens that disturbs vision, is part of the natural ageing
process. Epidemiological data show an increased risk for cortical cataract with UVB exposure
from the sun (Taylor 1988, McCarty et al 2002, Sasaki et al 2002). The prevalence of the
blinding disease of cataract world-wide exceeds 50 million (Brian 2001, Thylefors 2001, WHO
1994). Animal experiments have clearly shown that UVR exposures produce cataracts, but
experts disagree on the degree of importance played by environmental solar exposure (Sliney
2002).
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