ETOX 80E - Beluga Whales

A Tale of Three Chemicals: DDT, PCB, and Dioxin

Hormone Disruptors

The Beluga Whales of the Saint Lawrence River

(from Béland, P., 1996, Scientific American 274: 74-81)

Historical Record:

Indian midden bone fragments (8500 bp)

reported by French explorer Jacques Cartier in 1535

commercial fishery 1600s (Basques) to 1979 (protected species)

population decline from 5-10,000 in 1800s to 500 in 1979

current population still 500 , in spite of 20 years of protection

previously attributed to low productivity and/or habitat degradation

Evidence of Pollution:

deaths from renal failure & infections

unusually high levels of mercury, lead, PCBs, DDT, Mirex, & other pesticides

organohalogens and mercury are lipophilic

high levels also found in other marine mammals (seals & porpoises)

halogens are associated with:

liver damage, gastric erosions, skin & gland lesions, & hormonal imbalance

Temporal (15 years) Study:

recorded 179 deaths & autopsied 73 carcasses

many exhibited stomach ulcers

commonly observed lesions of thyroid & adrenal glands

some had small amounts of milk because of:

infection, necrosis, or tumors in mammary glands

40% (21) of the animals bore tumors

14 of the tumors were cancerous,

"representing more than half of all malignancies ever reported in cetaceans"

(reader: is this a fair use of statistics ?)

disproportionate number of bacterial and protozoan infections

-> compromised immunity (immune cells altered by toxins)

multisystemic diseases

one true hermaphrodite

-> xenoestrogens

Food Chain Perturbations:

anomalously high levels of benzo(a)pyrene (carcinogen) in sediments (Al plant)

belugas feed on benthic invertebrates ( ingest BaP)

too much Mirex, based on food chain calculations

Mirex contamination in eels migrating from lake Ontario (>> Mirex in fish)

no reduction in DDT over generations (conc. females < males, highest in young)

40% body weight is blubber (85% fat tissue)

organohalogens recycled and concentrated in motherís milk (35% fat)

PCBs in milk 10 ppm (2 ppm max for human consumption)

PCBs in calf blubber (60 ppm) twice motherís blubber (30 ppm)

The American peregrine falcon (Falco peregrinus anatum) is an endangered species. As a carnivore at the top of an avian food chain, it was brought to the verge of extinction by its bioaccumulation of DDT. This bioaccumulation was sufficient to cause egg shell thinning that decreased reproduction. This phenomena was first recognized in the brown pelican (Pelecanus occidentalis) by Bob Risebrough, who was previously associated with the Institute of Marine Science at UCSC. The peregrine falcon was probably saved from extinction in California by Brian Walton and his colleagues in the Predatory Bird Group at UCSC.

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