Industrial Contaminants

Persistent Organic Pollutants in Great Blue Heron and Cormorant Eggs

Pattern of toxic equivalents (parts per trillion) of industrial organochlorines in great blue heron eggs.

Crofton is a pulp and paper mill site; UBC (University of British Columbia) is an urban site; Nicomekl is a rural site.

Concentrations of pollutants in great blue herons eggs in the Georgia Basin have been decreasing since the 1970s.

The decrease reflects the trend in contaminants in the local environment. Long-term studies in the Georgia Basin show:

• Since the 1970s, PCBs, dioxins, and furans in heron eggs have dropped as controls on these pollutants were put in place. PCB concentrations in cormorant eggs (not shown on graph) also dropped.

• Until 1990, the Crofton colony, near a pulp mill, was the most contaminated by dioxins and furans. Contaminants dropped sharply as pulp mills complied with regulations to eliminate these chemicals from effluent.

• The University of British Columbia herons, which feed in the Fraser River estuary, were the most contaminated with PCBs. Levels dropped after controls on PCB releases in North America were put in place in the 1970s.

• The rural colony (Nicomekl) was least exposed to PCBs, dioxins, and furans (note the different scale for this graph).

• Since the 1970s, organochlorine pesticides, such as DDE, dieldrin, and chlordane (not shown), in heron eggs have also decreased.

For detailed information, including graph data, see In-Depth report [pdf].

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