|Monthly Tech-Tip |
1-Injuries Due to Ionizing Radiation :
X-rays, beta rays, and other radiation sources in adequate doses can cause ocular injury.
The eyelid is particularly vulnerable to x-ray damage because of the thinness of its skin. Loss of lashes and scarring can lead to inversion or eversion (entropion or ectropion) of the lid margins and prevent adequate closure.
Scarring of the conjonctiva can impair the production of mucus and the function of the lacrymal gland ducts, thereby causing dryness of the eyes.
X-ray radiation in a dose of 500-800 R. directed toward the lens surface can cause cataract, sometimes with a delay of several months to a year before the opacities appear
2-Injuries Due to Ultraviolet Radiation :
Ultraviolet radiation of wave lengths shorter than 300 nm. (actinic rays) can damage the corneal epithelium. This is most commonly the result of exposure to the sun at high altitude and in areas where shorter wave lengths are readily reflected from bright surfaces such as snow, water, and sand.
Exposure to radiation generated by a welding arc can cause welding flash burn , a form of keratitis.
Wavelenghts of 300-400 nm. are transmitted through the cornea, and 80% are absorbed by the lens, where they can cause cataractous changes.
Epidemiologic studies suggest that exposure to solar radiation in these wave lengths near the equator is correlated with a higher incidence of cataracts.
They also indicate that workers exposed to bright sunlight in occupations such as farming, truck driving and construction work appear to have a higher incidence of cataract than those who work primarily indoors.
Experimental studies have shown that these wave lengths cause changes in the lens protein, which lead to cataract formation in animals.
3-Injuries Due to Visible Radiation (Light):
Visible light has a spectrum of 400-750 nm. If the wavelengths of this spectrum penetrate fully to the retina, they can cause thermal, mechanical, or photic injuries.
A) Thermal injuries:
They are produced by light intense enough to increase the temperature in the retina by 10-20C.
Lasers used in therapy can cause this type of injury. The light is absorbed by the retinal pigment epithelium, where its energy is converted to heat, and the heat causes photocoagulation of retinal tissue.
They can be produced by exposure to laser energy from a Q-switched or mode-locked laser, which produces sonic shock waves that disrupt retinal tissue.
They are caused by prolonged exposure to intense light , which produces varying degrees of cellular damage in the retinal macula without a significant increase in the temperature of the tissue.
Sun gazing is the most common cause of this type of injury, but prolonged unprotected exposure to a welding arc can also damage the the retinal macula. There may be permanent decrease in visual acuity.
The intensity of light, lenght of exposure, and age are all important factors. The older ones are more sensitive, also those who have had cataract surgery because filtration of light by the lens is impaired.
4-Injuries Due to Infrared Radiation:
Potters may be exposed to this type of radiation.
Wavelenghts greater than 750 nm. in the infrared spectrum can produce lens changes.
La "cataracte des verriers"( glassblower's cataract ) is an example of a heat injury that damages the anterior lens capsule among unprotected artists. Denser cataractous changes can occur in unprotected workers who observe glowing masses of glass or iron for many hours a day.
Another important factor is the distance between the worker and the source of radiation. In the case of arc welding, infrared radiation decreases rapidly as a function of distance, so that farther than 3 feet away from where welding takes place, it does not pose an ocular hazard anymore but, ultraviolet radiation still does. That is why welders wear tinted glasses and surrounding workers only have to wear clear ones.
When we speak of type of exposure, potters look at their cone packs for very short periods of time in a repeated way, more often nearing the end of firing; and also according to the use of other methods for measuring temperature, like the concomitant use of a thermocouple and a reading device.
So, these " short-term " exposures are spaced by quite longer " exposure-free " periods and the sum of the former does not correlate with the concept of "many hours a day".
We have searched the literature pertaining to Occupational Health and Safety and have not found a single case of presumed " ceramicist's or potter's cataract ", even if the trade of potter is quite older than the one of glassblower.
Therefore, I do not think that any of the above types of radiation present a threat to potters.
It is a good thing, mainly at high temperature, to wear lightly tinted industrial grade safety glasses to better visualize cones(ocular ergonomics) and also to reassure those who are more worried.
These glasses also offer a better protection than typical sun-glasses in case of projection of hot dust particles from a gas kiln when looking through the peephole in a soft brick door.
By the way with ageing, most if not all of us, will suffer from cataracts of the "senile" type.
The progress or change and the related reduction in vision is usually quite slow.
Nuclear sclerosis-an increasing density in the central mass of protein-causes a myopic change than can be corrected by changing glasses for some years-in many instances restoring vision to near normal.
1-Occupational & Environmental Medicine, Joseph Ladoue & al, last
2-Occupational Medicine, Zenz C., last edition.
3-Precis de Medecine du Travail, Desoille H., Scherrer J., Truhaut R., last edition.
4-Oshline & Nioshtic database.
By Edouard Bastarache
Article by Edouard Bastarache
Edouard Bastarache is a well known doctor that has written many articles on the subject of toxicity of ceramic materials and books on technical aspects of ceramics. He writes in both English and French.