Well it shows you don't know very much about chemistry and aviation then! Let me give you clue as to one of the most important ingredients to some quite lethal gasses such as:
Phosgene gas (WWII)
Mustard gas (WWI)
Chloroform.
You guessed it...Chlorine!
So now we have your bargain basement bucket of chlorine in the hold of an aircraft. What if the aircraft enountered some turbulence and the bucket spilled out some chlorine and someone elses suitcase also opened and spilled out that contained something made of copper, aluminium, alchohol? We get a chemical reaction that could cause several effects such as burning, accellerated corrosion to the aircraft's ALUMINIUM skin leading to an explosive decompression, production of lethal gas that is recirculated into the main cabin air supply, (90% of air in a pressurised aircraft is recycled). So if that's not endagering lives, what is???
A lot of frieght comes to this country by air, but I would be surprised to see an aircraft carrying several tonnes of pool chemicals. Not to say that it can't be done, you can ship DAC (dangerous air cargo), but you need a licence, and the procedures are usually very prohibitive.
I hope that answers your question!
Beeza