Re: UV protective material

[Eric Cowdrey <ericc@mctrf.mb.ca>]

At 10:16 AM 12/2/97 -0600, you wrote:

>I have a question from a lab and have been unable to find an answer 
>in my texts and manuals.
>
>The question: We have a UV light box which produces a 312nm 
>wavelength for viewing ethidium bromide agarose gels.  It uses 6, 15 
>watt bulbs.  We need to buy a shield and the catalog offers a 
>polycarbonate or an acrylic material.  Which is sufficient for this 
>wavelength?  Both?  Is the only difference one of strength?  
>
>I have no text which discusses materials except in a general way and 
>I view this as a chance to broaden my knowledge of UV....so if anyone 
>can answer the question(s) AND offer advice on text, I would 
>certainly appreciate it.
>
>If you don't think the list needs the info, please respond directly 
>to me.
>
>george@pliny.ehs.ufl.edu
>George Rawls
>University of Florida
>Health Physicist
>george@pliny.ehs.ufl.edu
>
When buying a shield for a UV source, I would first look for the
manufacturer's statement that the material is intended for this purpose.
The manufacturer might also be able to supply an attenuation factor as a
function of UV wavelength, but this in itself may not be entirely useful
because the shield could be used with a wide variety of source strengths.
It will be necessary to make some UV irradiance measurements (using an
appropriate UVA meter that measures total UVA irradiance in mW/cm**2) under
the actual conditions of use (i.e., at the locations where the unprotected
skin of the face and hands of a user would be situated) to evaluate the
effectiveness of the shield.  Then, you would calculate the permissible
exposure time using the TLV values (which are based on continuous exposure
for an 8 hour day) given in the American Conference of Governmental
Industrial Hygienists (ACGIH) TLV booklet; the 1996 issue gives a TLV of
200 mJ/cm**2 at a wavelength of 310 nm and 500 mJ/cm**2 at 313 nm, so that
it would be necessary to interpolate for 312 nm.

*************************************************

Eric Cowdrey
Radiation Protection Officer
Department of Medical Physics
Manitoba Cancer Treatment and Research Foundation
100 Olivia Street
Winnipeg, Manitoba  R3E 0V9
CANADA

Telephone: (204) 787-2166/4145
Fax:       (204) 775-1684
E-mail:    ericc@mail.mctrf.mb.ca