Regarding water - There is an interesting story of two towns who relied upon the same water source for drinking water. One town became highly concerned with the levels of arsenic in the water so they invested heavily in a purification system that would take all of the arsenic out of the water. The second town didn't have the interest or money for such a system so the children of the second town grew up drinking water with trace levels of arsenic.
A few decades later, a trend developed between the two towns. One had a much higher rate of children developing asthma and other respiratory ailments than the other...it was the town that totally eliminated all arsenic from its drinking water.