[Sask Mark]

Some very good points are raised in this thread.

In order to dispell myths, the MSDS (material safety data sheet) for any substances encountered should be consulted. The msds will provide important pieces of information such as the LD50, routes of entry, treatments etc.

Now keep in mind that there are issues with relying exclusively on MSDS's. For one, the animals used to determine toxic and lethal levels are usually rodents, so extrapolating their effects to humans introduces some level of error. Secondly, (not necessarily bad) msds's tend to be far more cautious than what is required. For example, water has health hazards on it's msds. Another example is boric acid. If you read the msds, it is highly toxic. If you go to a doctor and require an eye wash, they will use boric acid. A third example is selenium. I used selenium tablets as a catalyst in a lab tech job I used to have. The msds raised all sorts of red flags when in fact toothpaste contained more selenium than the tablets I was using. Bottom line is you have to use some common sense when interpretting msds's.

Another challenge is determining what levels of a toxin you are encountering. Short of having expensive air quality tests that quantify specific toxins in the environment, there is really no way to tell if you are exposing yourself to hazardous levels of certain chemicals.

Yet another aspect to keep in mind is the route of entry. Many people are rightfully worried about inhalation of fumes. They also have to keep in mind their eyes which are effectively sponges which soak up many contaminants in the environment (eg. welding fumes). Safety glasses don't protect your eyes from fumes. Goggles do.

A final challenge is you are never really sure of what chemicals will be produced in certain activities. Welding is a chemical reaction where chemical compounds are consumed and produced. Unless extensive research has been conducted on the exact methods and materials that you are using, you are never sure when you will encounter.

A take home message would be if you can't be sure and want to ensure your safety, err on the side of safety. I used to work in a malt house, in chemistry labs and other industrial environments, and whenever there was a risk of exposure to almost anything, I wore a North 7800 FULL FACE respirator with Defender cartridges (respirators have their own set of challenges (like correct fit, beards prevent proper seals, lung capacity is reduced) and before wearing one, an expert should be consulted). I was routinely in environments with very high chlorine, SO2, and glaciel acetic acid levels. The company I worked for had a lot of liability resting on their shoulders if these safety standards weren't followed, so all our PPE (personal protective equipment) was supplied (safety is not cheap-the respirators were over $300 each).

Sorry for my long-winded post. I'm not a safety expert but I have been trained as a biologist, have worked in chemical labs, was the safety officer at previous jobs, and now work in the commercial/industrial construction industry (safety is paramount at my company and concrete has chromium hexavalent!). I figure if my experience can clarify (of muddy) something or makes someone think more critically about a situation, then I guess it's worth it!