Welcome to the forum!

Rich.

The AWS had a "Fact Sheet" which was #24 that spoke directly to your issue.  It is not on the AWS.org list currently and I don't know why..

This data was also published in the "Welding Journal" in the December issue 2002.

I have the PDF copy that was formerly available for free download from the AWS if you would like a copy just drop me an email and I'll attach it for you.

ANSI Z49.1  The American National Standard for Safety in Welding...Section 8.5 also provides good backup for a requirement to provide UV protection for passers by... Osha does as well.

Edit:

Hey... I got the PDF to attach!   thought it might be too big

Also I did finally find the link at AWS  http://www.aws.org/technical/facts/

And here is the link to download Z49.1  http://www.aws.org/w/a/survey/standard.html?survey_start=z49_reqpdf