WER Testing


EnviroScience biologists have extensive experience with culturing and examining many different species of freshwater, saltwater, and sediment organisms. Our toxicologists can customize study plans to meet numerous requirements for specialty projects meeting the needs of each individual client. Contact our Bioassay Laboratory about developing a special toxicity test for you.

Water Effect Ratio

EnviroScience’s Bioassay Laboratory performs Water Effect Ratio (WER) evaluations. Water Effect Ratios may be used to derive site-specific limits for certain metals from national and state aquatic life criteria that were originally developed using laboratory toxicity data.

The USEPA established federal guidelines to derive site-specific criteria for certain metals including arsenic, cadmium, chromium(III), chromium(VI), copper, lead, mercury, nickel, selenium, silver, and zinc. A number of physical and chemical characteristics of site water and a metal can affect the toxicity of that metal to aquatic organisms in particular surface water. When deriving site-specific aquatic life criteria for a metal, the difference between the toxicity of the metal in laboratory water and site water may be adjusted with a site water effect ratio.

Toxicity differences of site water and synthetic laboratory water are compared in the laboratory, and evaluated for differential lethal concentrations. The toxicity endpoints from these two tests are used to calculate the WER, which is then multiplied by the national or state aquatic life criterion to calculate the site-specific limit.


EnviroScience provides high quality environmental services to hundreds of satisfied municipal, industrial, and private sector clients throughout the Midwest and Northeast. We have clients in Ohio, Pennsylvania, West Virginia, Illinois, New York, Michigan, Indiana, Tennessee, and many other states. Our company has an excellent reputation with regulatory agencies on both the state and federal level. Our confidence in our methodology and the professionalism of our experienced biologists allows us to guarantee that our procedures and reported data will meet all acceptance criteria.

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