Q & A from Earlier Class on Risk and Safety

***Question: determining 'Safe': as I understand the word Safe should not be a
lexicon of a professional toxicologist. Safe is absence of unacceptable risk.
Who is deciding for me, for example, as worker what risk of harm is
acceptable?
A. We might say the word "safe," but we would need to be able to answer the question, who is it acceptable to. We sometimes note that something meets the government regulations. If we also think its risks are very low, we might say "I believe it is safe." If we do not have strong ideas about it, we might say, "It meets the OSHA regulations and is probably safe." It is much more professional to say "the risks are very small," than to say, "it is safe."

** Q. The split-up of effects in "Reversible" and "Irreversible" seems a little strict for me, it happens probably a lot between these both cases. Does a finer scheme exist?
A. Obviously, those are very general terms. If you want more detail, you would simply explain what the effect was.

** Q. What are the significance of ED10 (or other) apart from 10% of the object
being affected. While testing harmful effects on human beings from some thing,
if 10% are affected then we can not call it a safe thing. So generally how we
relate effective dose and safety standards?
A. If the effect were noticeable and harmful, we would never accept exposure of humans to a substance at its ED10. Sometimes it is acceptable for environmental systems if 10% of a species is harmed, if the substance does not linger, the species may recover without any long-term problems.

**Q.'Risk' seems to imply the occasion of 'accident' which implies a lack of
responsibility. Concerning industrial risk, do workers ever sign off on
responsibility for harm or is there a legal or union framework preventing
such a practice?
A complicated moral question, but easy legally. In the US, the employer is always 100% responsible for "work-related" injuries. Also the employer is 100% responsible for "work-related illnesses," although these are harder to prove. An employer cannot shed this legal responsibility to a worker, even if the worker deliberately disregards the employer's instructions. Employers are supposed to train unsafe workers, and then fire them if they persist.

** Q. Similar to toxicity, a 'safety' risk is also proportional to the degree
of activity (walking a dolly vs. carry 100+lbs) and everything could be
thought inherently dangerous and unsafe. So what is the parallel, dose-type
relationship for safety?
A. There are standards for the work environment. If these are met, the workplace is presumed safe, in that regard. So an open pulley and belt must have a guard. Having provided the guard, you have made the workplace "safe" in regard that pulley. For some items, such as weight that one can carry, there are formulae and tables, similar to LD50, etc., that specify what can be carried.

* Q. 1. We may not practically treat waste to 100% so we use some standard and set
a limit and below it we call safe and dispose them to the environment
(generally Water system,air or land). But on long run the hazardous materials
in the waste (which we had called safe as we had treated) may get accumulated
and become unsafe (example: Quality of air after 500 years later if we go on
polluting air at present safe rate). So, what about the present standards? how
practical are they? or are most of them established for solving the problems
for a short term.
A. We'll go into this a little later, but some contaminants are "bio-degradable" others are not. Some environmental systems seem to have the capacity to assimilate contaminants, others don't. The notion of "natural attenuation" is worth consideration. Now at one time industry believed and engineers were taught "dilution is the solution to pollution." Today we know that is often not true. However, in some cases it works fine. It depends on the contaminant and the receiving system.

Q. My question regarding the content goes hand in had with question #4 on the quiz. I understand that a high pressure tank exploding would be classified as a physical hazard. But, depending on what is inside the tank, the exposure to the contents could also be the source of acute health hazards. I got the question wrong on the quiz so please let me know where my thinking went wrong.
A. The danger from the tank exploding would be that of the safety engineer, not the IH. You would have to add something to the question about the contents of the tank to get to the next step. Clearly the IH would not do pressure or corrosion calculations relevant to the risk of explosion.

Go to Module 01 Index      Go to ENVE 649 Homepage