Some industrial chemicals which can damage the liver, kidneys and nervous system are often discharged into public water supplies. Currently tested water is considered pure if the amount of industrial chemicals an individual is exposed to, through drinking 2 liters of water per day does not pose a significant threat to human health. But many toxicologists claim that the standard set by this method does not adequately protect the public.
Which of the following if true would best support the claim of the toxicologists mentioned above?

Earthquakes, volcanic eruptions and unusual weather have caused many more natural disasters adversely affecting the people in the past decade than in previous decades. It can be concluded that the planet earth as a natural environment has become more inhospitable and dangerous and we should employ the weather and earth scientists to look for causes of this trend.
Which one of the following statements if true will most seriously weaken the above conclusion?