The United States Environmental Protection Agency maintains a list of Primary Drinking Water Standards that contains contaminants known to cause harm to humans, a list of Secondary Drinking Water Standards that contains contaminants known to cause aesthetic problems, and a list of what some people call 'emerging contaminants' that contains chemicals and compounds that scientists have detected in the global drinking water supply at trace levels but have not yet determined if they pose a risk to human health.
Items on the third list include things like personal health care products, prescription medications, over the counter medications, herbicides, pesticides, and other compounds that mankind has added to the products it uses on a daily basis.
Why have we not noticed some of these contaminants previously? Quite simply, advances in analytical techniques and its associated instrumentation has made it possible for scientists to detect them.
Should we worry about emerging contaminants? We should certainly keep an eye on their levels and monitor their effects on people, that's for sure!
Remember: In the not-too-distant past compounds like asbestos, lead, mercury, arsenic, and thousands of man-made chemicals got used all around the world without so much as a single person batting an eye or questioning their safety for the general public.
