This popular phrase "canary in a coal mine" came from the historic use of canaries as an early warning system in the coal mining industry. The canary is more sensitive to smaller concentrations of carbon monoxide and methane gases that would otherwise be undetectable to humans. Hence it would be the first to perish from toxic gases giving the miners enough time to evacuate.

Although canaries are no longer used in mining operations, we have adapted this system of examining animals in order to detect the presence of pollutants in our environment.

Did You Know?
Bioindicators are organisms that provide information on the health of the environment. They are monitored for chemical,physiological, and behavioural changes that could indicate a problem with the ecosystems in which they live.

One recent example of this practice is the detection of a group of man-made chemical pollutants called polychlorinated biphenyls (PCBs) in the tissue of dolphins living along coastal areas of the United States. It was found that high concentrations exist within dolphins residing near heavily industrialized areas where PCBs are emitted into neighbouring waters.

Did You Know?
PCBs are hydrophobic and highly halogenated organic structures that tend to accumulate in the fatty tissues of animals via inhalation, ingestion,and/or absorption through the skin, leading to toxic and carcinogenic effects.

Scientists have used a variety of organisms (e.g. clams, mussels, fish,etc) to monitor other persistent organic pollutants (POP) in aquatic environments. The results from these studies not only help them to identify possible sources of pollutants, but also assist in evaluating the risks to human health.

Researchers have also taken advantage of the fact that animals attempt to eliminate foreign compounds from their body through the induction (or production) of certain metabolizing enzymes (e.g. cytochrome P450) and other types of detoxifying proteins. With this knowledge scientists are able to indirectly detect the presence of specific pollutants in the environment. One such example is the analysis of a group of proteins known as metallothionein, which are produced in response to exposure to heavy metals (e.g. mercury, copper, zinc, lead,cadmium). Hence researchers can use fish to quantify their metallothionein levels as a means of detecting metal contamination in the water that could potentially be harmful to humans.

Another way to assess the health of the environment is by examining the number and types of organisms that are present. For example,an increase in pollution tolerant aquatic insects (or decrease in pollution-sensitive ones) would indicate damage to an ecosystem.. Monitoring for abnormal changes in the cellular structure or behaviour of bioindicators can also be used to detect if an ecosystem is being affected by pollution.

Bioindicators are not just restricted to aquatic animals. Organisms such as plants, birds, and bacteria are also used to provide an early warning of environmental stress. As with the canary in the coal mine of yesteryear, these modern-day bioindicators can help us prevent or minimize damage to ecosystems before it’s too late.

Learn More!

Bioindicators: Using Organisms to Measure Environmental Impacts

Persistent Organic Pollutants


Kucklick, J., et al. 2011. Bottlenose Dolphins asIndicators of Persistent Organic Pollutants in the Western North Atlantic Oceanand Northern Gulf of Mexico. Environ. Sci.Technol. 45: 4270-4277


Peng, J.H. et al. 2007. Determination of polybrominated diphenyl ethers (PBDEs)in fish samples from rivers and estuaries in Taiwan. Chemosphere. 66:1990-1997.

Verlecar, X.N. et al. 2006. Marine pollution detection through biomarkers in marinebivalves. Current Science. 91: 1153-1158.

Article first published January 13, 2011


Currently pursuing a Master's degree, I'm working on the post-harvest biochemistry of apple storage disorders. In other words, I'm trying to find out why apples turn brown after they've been picked off the tree and before their peels have been removed. When I'm not busy observing apples, I like to read, go ice skating, watch old TV shows on DVD, and cook! Fun (or not so fun) fact about myself: just the sight, sound, or touch of chalk makes my teeth chatter.

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