Environment Canada monitors water quality in areas where shellfish are harvested.
To be safe for human consumption, shellfish must live and be harvested in beds where the quality of the water meets very stringent standards. It sometimes happens, though, that the marine environment where these creatures live is polluted by municipal wastewater, wastewater from poorly maintained septic tanks and sumps, untreated industrial waste, run-off from farmland and feedlots, chemical contamination, etc. Eating shellfish from polluted waters is hazardous to the health.
Environment Canada analyses the bacteriological quality of the water of shellfish beds and recommends closing beds where the water is found to be polluted. This department also works with various other government agencies and local communities to get closed beds reopened.