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30 Year Old Research Still Resonates

By Laura Hall
July 2010

David  Miller, Ph.D.
"Seabirds can ingest oil by preening, drinking sea water, or eating contaminated food," said Miller. "The scary part about the results is that only one small dose is likely to give the birds problems with long-term survival." He added, "Nestling herring gulls experienced a 40 to 80 percent reduction in weight gain after one dose of crude oil." (Photo courtesy of Steve McCaw)

The NIEHS has played a key role in the federal government's response to the massive April 20 Deepwater Horizon oil spill. The NIEHS effort drew upon 24 years of experience providing safety training to emergency responders and hazardous materials workers through the NIEHS Worker Education and Training Program ( (See related story ( The NIEHS will also fund research on the health effects of the oil spill, which reminded one of NIEHS scientists of some related work he had done decades ago.

Early in his career before joining NIEHS, David Miller, Ph.D., now chief of the NIEHS Laboratory of Toxicology and Pharmacology, studied the physiological effects of Louisiana crude oil ingestion on seabirds. This research, which was done in the late 1970s and early 1980s, was partially funded by NIEHS and the Canadian Wildlife Service.

The studies reported what happened to several species of seabirds after ingestion of a single small dose -- 0.2 to 1.0 milliliter -- of crude oil. Birds that ingested oil showed marked reductions in weight and other sub-lethal toxic effects that could have reduced their ability to survive long-term. The birds tested included nestling herring gulls (Larus argentatus), nestling black guillemots (Cephus grylle), and Leach's Storm-petrels (Oceanodroma leucorhoa). Miller conducted the research both in the laboratory and in the field, on islands where the birds nested.

Endocrine and functional disruption

The data suggested that endocrine disruption was one underlying cause of the reduced growth in young birds. The oil-dosed birds also displayed salt and water balance or osmoregulatory impairment, as well as hypertrophy -- abnormal enlargement of the constituent cells -- of adrenal and nasal salt glands. Oil dosing reduced nutrient absorption in the intestine and hypertrophy of the liver.

Heavily oiled Brown Pelicans captured at Grand Isle, La. on June 3.
Heavily oiled Brown Pelicans captured at Grand Isle, La. on June 3, wait to be cleaned of Gulf spill crude at The Fort Jackson Wildlife Care Center in Buras, La. In Miller's experiments, only small sections of the birds were covered with four grams of oil or emulsion - just enough to see if there was an effect.  (Photo courtesy of Jay Holcombe and the International Bird Rescue Research Center)

In addition, adult petrels dosed with Prudhoe Bay crude oil were impaired in their ability to provide food for their chicks. Petrel chicks of oil-dosed adults had reduced survival as well as reduced growth rates.

Insight into the effects of dispersants

Miller's team also compared the effects of Corexit, an oil dispersant, an oil/Corexit emulsion, and oil exposure alone in herring gull nestlings. Ingested dispersant had no effect on weight and the effects of emulsion were no different from those of oil. However, when emulsion was applied externally on the birds, body weight declined and thyroid hormone levels increased. No such changes were seen when oil alone was applied externally. The scientists suggested that external emulsion primarily altered the birds' energy metabolism, probably to compensate for heat loss.

Weight loss in nestlings that continues after fledging can decrease long-term survival in ocean birds. Not only must these young birds find their own food, but after fledging many undertake long migrations or travel far into the ocean. Lowered body weight puts them at a competitive disadvantage.

Persistent toxicity

Normally, crude oil rapidly weathers after a spill, losing the more volatile and water soluble components within a few hours. However, Miller and his colleagues found that the weathering of South Louisiana crude oil did not alter its toxicity and that the higher molecular weight aromatic compounds -- polynuclear aromatics with three or more ring structures -- were responsible for toxicity in the birds.

(Laura Hall is a biologist in the NIEHS Laboratory of Toxicology and Pharmacology currently on detail as a writer for the Environmental Factor.)

Effects of Crude Oil Ingestion on Seabirds

Miller's studies of seabirds were published between 1978 and 1985. Citations to articles available on line or abstracted by the National Library of Medicine contain links. Studies that were not abstracted or, in some cases, not even indexed by PubMed may be available through inter-library loan or in some library collections.


Miller DS, Kinter WB, Peakall DB ( Exit NIEHS. 1978. Ingestion of crude oil: Sublethal effects in herring gull chicks. Science 199:315-317.

Peakall DB, Miller DS, Kinter WB ( Exit NIEHS. 1979. Physiological Techniques for assessing the impact of oil on seabirds. In: Avian and Mammalian Wildlife Toxicology (Kenaga EE, ed.). Philadelphia, Pa: American Society for Testing and Materials, 52-60.

Peakall DB, Miller DS, Butler RG, Kinter WB, Hallett, D. 1980. Sublethal effects of crude oil on Black Guillemots: A combined field and laboratory study. Ambio 9:28-30.

Peakall DB, Tremblay J, Kinter WB, Miller DS. 1981. Endocrine dysfunction in seabirds caused by ingested oil. Environ Res 24:6-14.

Miller DS, Hallett DJ, Peakall DB. 1982. Which components of crude oil are toxic to young seabirds? Environ Toxicol Chem. 1:39-44.

Peakall DB, Kinter WB, Miller DS. 1983. Toxicity of crude oils and their fractions to nestling herring gulls 1. Physiological and biochemical effects. Marine Env Res 8:63-71.

Trivelpiece W, Butler RG, Miller DS, Peakall DB. 1984. Reduced survival of chicks of oil-dosed adult Leach's Storm-Petrels. Condor 86:81-82.

Peakall DB, Jeffrey DA, Miller DS. 1985. Weight loss of herring gulls exposed to oil and oil emulsion. Ambio 14:108-110.

Jeffrey DA, Peakall DB, Miller DS, Herzberg GR ( Exit NIEHS. 1985. Blood chemistry changes in food-deprived herring gulls. Comp. Biochem Physiol 81A:911-913.

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