“Sensitive” humans are not defective or here to inconvenience you.
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Some canary history:
“Carbon monoxide, a potentially deadly gas devoid of color, taste or smell, can form underground during a mine fire or after a mine explosion.
Today’s coal miners must rely on carbon monoxide detectors and monitors to recognize its presence underground. However, before the availability of modern detection devices, miners turned to Mother Nature for assistance.
Canaries — and sometimes mice — were used to alert miners to the presence of the poisonous gas. Following a mine fire or explosion, mine rescuers would descend into the mine carrying a canary in a small wooden or metal cage.
Any sign of distress from the canary was a clear signal that the conditions underground were unsafe, prompting a hasty return to the surface.
Seriously "Sensitive" to Pollution 