Journal of Environmental Biology

Risk assessment of the amnesic shellfish poison, domoic acid,

on animals and humans

K. Prem Kumar¹,  Sreeletha Prem Kumar² and G. Achuthan Nair*³

¹Enbiomon, 1205 Seaton et, Montgomery, Alabama - 36117, USA

²Alabama Department of Environmental Management, Montgomery, Alabama - 36110, USA

³Department of Environmental Sciences, University of Kerala, Kariavattom, Thiruvananthapuram - 695 581, India

(Received: August 13, 2007; Revised received: December 28, 2007; Accepted: February 20, 2008)

Abstract: Risk assessment of the amnesic shellfish poison, domoic acid, a potent neurotoxin, is evaluated based on its current knowledge and its harmful effects, and is presented under four headings, viz., (1) hazard identification,  (2) dose response assessment,  (3) exposure assessment and (4) risk characterization. Domoic acid binds the glutamate receptor site of the central nervous system (CNS) of humans and causes depolarization of neurons and an increase in cellular calcium. In nature, domoic acid is produced by the algae, Pseudonitzschia spp. and they enter into the body of shellfish through their consumption. This toxin is reported to cause gastroenteritis, renal insufficiency, confusion and memory loss in humans, since it affects the hippocampus of the brain. In rats, intraperitonial and oral administration of domoic acid result in scratching, tremor and convulsions, and in monkeys, the toxic symptoms like mastication, salivation, projectile vomiting, weakness, teeth grinding and lethargy are apparent. The no-observed-adverse-effect-level (NOAEL) in animals reveals that pure toxin is more effective than those isolated from shellfish. Based on LD₅₀ values, it is found that intraperitonial administration of this toxin in animals is 31 fold more effective than oral administration. Low levels of domoic acid (0.20 – 0.75 ppm) show no toxic symptoms in non-human primates, but clinical effects are apparent in them and in humans, at a concentration of 1.0 ppm. The tolerable daily intake (TDI) of domoic acid for humans is calculated as 0.075 ppm, whereas for razor clams and crabs, the TDI are 19.4 and 31.5 ppm respectively. The hazard quotient (HQ) is found to be 2.  Being an irreversible neurotoxin, domoic acid has severe public health implications.  Death occurs in those above 68 years old.  In order to ensure adequate protection to public health, the concentration of domoic acid in shellfish and shellfish parts at point of sale shall not exceed the current permissible limit of 20 mg g^-1 tissue.  While processing shellfish, it may be advisable to pay attention to factors such as environmental conditions, inter-organ variability in concentrations of domoic acid  and cross contaminations.

Key words: Domoic acid, Neurotoxin, Public health, Risk assessment, Shellfish, Tolerable daily intake

PDF of full length paper is available with author (* gachuth@yahoo.com.)

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