Timing of uptake and loss of WP and the onset of pathology in mallards

and breeding condition (after laying) as in 1993.

that the average number of eggs laid was signifi-

We determined that the LD50 for adult females

cantly fewer than either the placebo or control

was 6.8 mg/kg, which was not statistically differ-

birds. Only nine young developed from eggs at

ent from that for adult males. However, adult

the lower dose and only one of these hatched.

females have a much shallower dose-response

Three embryos that failed to hatch had terato-

curve than adult males (P <0.0001). This shallow-

genic deformities. Deformities included scoliosis,

er slope makes predictions of mortality at specific

lordosis, submandibular edema, microphthal-

dose levels less certain and also changes the risk

mia, and spina bifida.

assessment characteristics for adult females com-

Timing of uptake and loss of WP and the

pared to males.

onset of pathology in mallards

The uptake and loss of white phosphorus from

Confirmation of acute toxicity and lowest observable

living tissues is important because of the possibil-

effects level with pelletized white phosphorus

ity of secondary toxicity and human health per-

Much of the work on acute toxicity of other

spectives associated with waterfowl hunting.

compounds suspends the compound in a carrier

Obviously, the risk of secondary exposure is relat-

such as water or corn oil. Our initial experiments

ed to the retention time of WP in tissues. Adult

used the same approach for comparability but

waterfowl at Eagle River Flats are exposed to pel-

mallards were gavaged with a single dose of

letized WP. Thus, we conducted a small test to

pelletized white phosphorus at 1, 2, and 4 mg/kg

compare the acute toxicity of pelletized WP to

and then sacrificed at 3, 6, 12, 24, 96, and 240

that dissolved in oil. Fourteen male mallards

hours after dose. Birds were necropsied for obvi-

were given a single dose of WP at 6.5 mg/kg.

ous organ damage and fat, liver, kidney, breast

Twelve died, which was greater than the

muscle, and brain were harvested for residue

expected number of seven (P <0.05). Thus, pellet-

determinations. Of the 12 birds dosed at 4 mg/

ized white phosphorus is more toxic to adult

kg, 10 died within 24 hours after dose. The two

male mallards than is white phosphorus dis-

survivors at this dosage were sacrificed at 240

solved in oil. Based on other studies that were

hours; one appeared healthy and unaffected

conducted in 1994, we estimate that the LD50 for

whereas the other had severe necrosis in approxi-

mately half of its liver and trace levels of WP in its

pelletized WP is between 3 and 4 mg/kg. To

fat. We surmise that the healthy bird had proba-

determine the subacute effects of pelletized white

bly orally voided the pellet shortly after dosing.

phosphorus, we dosed 10 males at each of two

At 1 and 2 mg/kg, white phosphorus was assimi-

levels, 2.4 and 3.4 mg/kg daily for 10 days. At 2.4

lated within the first 3 hours after exposure,

mg/kg, three mallards died but not until the

reached peak levels in fat within 612 hours after

eighth dose. One bird that was debilitated for 3

dose, and was at or near detection limits within

days after the last dose had a pellet lodged in its

48 hours. Liver levels increased during the first 3

gizzard, indicating that birds can hold pelletized

hours but rapidly dropped to detection levels by

WP for several days after ingestion. Of 10 mal-

24 hours after dose. Muscle and kidney levels

lards dosed at 3.4 mg/kg, 6 died during the

were very low and essentially gone within 12

study, the first after two doses. One survivor also

hours after dose. No WP was detected in brain tis-

had a smoking gizzard four days past the last

sue. Fatty livers appeared in a few birds as early

exposure. Pathological damage was extensive in

as 3 hours after dose at the 2-mg/kg level.

both groups of birds and included fatty liver

degeneration, liver necrosis, kidney damage,

Adult female mallard acute toxicity

decreased hematocrit and hemoglobin, decreased

Work conducted during 1993 allowed us to de-

number of lymphocytes, and elevated heterophil

termine that the LD50 of WP dissolved in oil for

counts. Our lowest dose was above the lowest

adult males was 6.4 mg/kg and that there was no

observable effects level (LOEL) for repeated doses

difference between adult males and juvenile

because 1.3 mg/kg can alter reproduction in

birds of either sex. However, adult females

females, but we estimate that the LOEL for single

appeared to be much less sensitive to WP than the

doses is approximately 12 mg/kg.

other agesex classes and we were unable to con-

firm an LD50 for this group. In 1994 we repeated

Secondary toxicity of WP in

our acute toxicity experiment with adult females

American kestrels fed treated chicks

at the same time of year (late Julyearly August)

To assess the potential for secondary toxicity,

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