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How Water Is Tested for Cyanotoxins Using Enzyme-Linked Immunosorbent Assay (ELISA)

When conditions are just right—such as found on warm, sunny days in the summer—small organisms called blue-green algae (or “cyanobacteria”) grow and may multiply rapidly in oceans, lakes, rivers, ponds, and other bodies of water.

As they eat, reproduce, and die, some of these cyanobacteria may produce and release different types of cyanotoxins, which can make people sick if they drink the water. By regularly testing water samples for the presence of these cyanotoxins, water quality specialists can make decisions about treating the water to reduce or remove the toxins or advise the community when it may not be safe to drink or play in the water.

 water sample from big cliff dam and cyanotoxin testing rack

As part of a rigorous water quality monitoring program, skilled City of Salem Public Works employees collect, track, and test water samples from various locations in the watershed, water treatment facility at Geren Island, and water distribution system. Microcystin and Cylindrospermopsin are two types of cyanotoxins caused by blue-green algae (or “cyanobacteria”) that the City can test for at its in-house lab using enzyme-linked immunosorbent assay (ELISA).

 lab technician at willow lake prepares water samples next to caas equipment

A City of Salem certified lab technician prepares water samples for testing using a cyanotoxin automated assay system (CAAS) at its in-house lab. This specialized equipment allows the City to use enzyme-linked immunosorbent assay (ELISA) to test the water for any concentration of cyanotoxins by measuring how much blue light the water will absorb. Results are sent to water quality staff who review, track, and use the data to make decisions about drinking water treatment.

How ELISA works

One reliable method experts often use to test water for the presence of cyanotoxins is called enzyme-linked immunosorbent assay, abbreviated ELISA (pronounced “ee-LIE-zuh”). Here is how it works.

icon two test tubes 

A water sample is collected, and a small part of the sample is placed into a vial.

icon graph 

Test result data are sent to water quality staff at the City, who review and track the data. If test results show high levels of cyanotoxins are in the source water above the treatment facility, more water samples are taken from other locations in the drinking water distribution system to be tested.

lab technician gloved hand pours water sample into vialweb_1600x1067_color

The enzyme-linked immunosorbent assay (ELISA) testing that the City of Salem performs in its in-house lab is the recommended testing method under Oregon’s new rules adopted June 29, 2018, by Oregon Health Authority.



lab technician at willow lake puts elisa samples in freezer

Before water samples can be accurately tested for the presence of cyanotoxins, the samples must be frozen and thawed three times to rupture (or “lyse”) any blue-green algae cells the water may contain. A cryogenic freezer is part of the City of Salem’s ELISA equipment at its in-house lab. By using an in-house lab, the City can receive and share test results as quickly as possible.


 lab technician hand preparing water samples for elisa testing and computer

A lab technician prepares water samples to test for the presence of any cyanotoxins. As of June 2018, the City of Salem is one of only two organizations in Oregon that have the equipment to run enzyme-linked immunosorbent assay (ELISA) testing.

water sample vials in caas rack for elisa testing

Carefully labeled samples are loaded into the cyanotoxin automated assay system (CAAS) at the City of Salem lab. The equipment will use an enzyme-linked immunosorbent assay (ELISA) to test the water for any cyanotoxins that may have been produced by blue-green algae that grow during the summer in the North Santiam River and Detroit Lake watersheds.

Some words explained


A verb that means to take in or soak up a substance by chemical or physical action, usually gradually


A test to determine what or how much something contains or is made of


Cyanotoxin automated assay system, lab equipment for running an ELISA test


Related to very cold temperatures or deep-freezing


A poisonous substance produced by cyanobacteria, also called blue-green algae. Some types of cyanotoxins that ELISA detects are Microcystin and Cylindrospermopsin.


Enzyme-linked immunosorbent assay, a method of detecting and measuring cyanotoxins in water


To keep at a suitable temperature or in favorable conditions to cause a certain reaction


The disintegration of a cell by rupture of the cell wall or membrane


A unit used to measure the visible light spectrum