Folks, just so that you can put human health effects in perspective from the standpoint of tap water, you should realize that EWG's "health guideline" for a particular contaminant is somewhat suspect. EWG is an advocacy group, and wikipedia includes this statement:
"The accuracy of the EWG reports and statements have been criticized, as has its funding by the organic lobby.[2][3][4][5] Its warnings have been labeled "alarmist", "scaremongering" and "misleading". "
The general statement about popular science articles and websites about the risk of environmental contaminants is that they strongly lack perspective. Many of these contaminants noted by EWG as "potential effect: cancer" have only a theoretical link to human metastasis. Even in the case where there is no doubt about a causative link between an environmental contaminant and human cancer, such as radon exposure, the additional risk at the levels that are regulated in municipal water supplies is
tiny.
To understand this point, let's examine the risk of arsenic. Arsenic is a known carcinogen, with a positive link to certain human cancers. Rice as a crop often has elevated levels of arsenic compared to other grains because of the way it's grown and the regions where it's grown. The additional risk has been extensively analyzed, and approximately speaking, the risk of the arsenic contained in rice is 39 additional cancers per million individuals in the population for someone eating rice 3 to 4 times a week, with a 90% confidence interval between 0 and 79.
On the face of it, to some in our population that sounds unacceptably risky. However, one needs to understand that the
total risk of developing cancer of any type is about 390,000 out of a million. So even calculating the additional risk of a
known human carcinogen is quite difficult over the "noise" in the data set.
www.researchgate.net
