Emerging Contaminants: The NSF List

The list of possible new water contaminants is endless, since new chemicals are issued much faster than regulators can test them.

Traditionally, ANSI/NSF certification has been divided into two categories: the contaminants with known adverse health effects, like arsenic, and items like the taste and color of water, which are aesthetic issues not known to affect health.

Emerging contaminants are a new category of water quality concerns for which evidence of health effects has not yet been established due in part to the trace levels at which these compounds are currently being detected.

The newer chemicals that are being listed by regulatory agencies are seen below in the Emerging Contaminants list being tested to a new NSF standard called American National Standard NSF/ANSI 401.  You’ll see some familiar names in the list. Yes, DEET is the stuff you spray on your body to discourage mosquitos,  Ibuprofen is what you take for a headache, and Bisphenol A (aka BPA) is the ingredient in plastic bottles you’ve been trying to avoid.

Note that the allowable amount for all of  these is expressed not in parts per million, or parts per billion, but in ng/L, nanograms per liter.  One nanogram per liter is one one-millionth of one milligram per liter. Expressed differently, one nanogram per liter is the equivalent of one part per million of one part per million of the whole. When you think of it as slicing a pie into a million pieces then one of the pieces into a million pieces, that isn’t much.

To understand how NSF testing is done, what the chart tells you is that if they take a solution containing more or less 200 ng/L of the angina and blood pressure medicine Atenolol and put it through a filtration device, the device must reduce the Atenolol content to 30 ng/L or less to receive NSF certification.

It is noteworthy that the fairly short list of devices that have attained NSF certification for removal of Emerging Contaminants includes only carbon filtration devices, and some of these are small devices like refrigerator filters or pitcher filters. The moral is that if you drink water from a good carbon-based drinking water filter, or a reverse osmosis unit, you can safely stop worrying about being overcome by the page-long list of health problems associated with the anti-seizure drug Carbamazepine.


Substance Average influent challenge ng/L* Maximum effluent concentration ng/L*
Meprobamate 400 ± 20% 60
Phenytoin 200 ± 20% 30
Atenolol 200 ± 20% 30
Carbamazepine 1,400 ± 20% 200
TCEP 5,000 ± 20% 700
TCPP 5,000 ± 20% 700
DEET 1,400 ± 20% 200
Metolachlor 1,400 ± 20% 200
Trimethoprim 140 ± 20% 20
Ibuprofen 400 ± 20% 60
Naproxen 140 ± 20% 20
Estrone 140 ± 20% 20
Bisphenol A 2,000 ± 20% 300
Linuron 140 ± 20% 20
Nonyl phenol 1,400 ± 20% 200



Source of NSF Chart.