Award Date

5-2009

Degree Type

Thesis

Degree Name

Master of Public Health (MPH)

Department

Environmental and Occupational Health

First Committee Member

Shawn Gerstenberger, Chair

Second Committee Member

Chad Cross

Third Committee Member

Michelle Chino

Graduate Faculty Representative

Timothy Farnham

Number of Pages

67

Abstract

Lake Mead is the largest reservoir by volume in the United States and provides fishing opportunities for numerous anglers. Considerable attention has been given to the bioaccumulation of methylmercury in fish tissues, however, no formal study utilizing approved USEPA methodology has been conducted to quantify the amount of mercury present in fish tissue from Lake Mead. The purpose of this study is to determine the concentrations of mercury present in the most commonly consumed fish from Lake Mead and to identify if any of the 4 major basins contain fish with elevated concentrations of mercury. Largemouth bass (n=49), striped bass (n=94), and channel catfish (n=78) were collected from selected sites in Boulder Basin, Overton Arm, Virgin Basin, and Gregg Basin of Lake Mead by gill netting or electrofishing. Muscle tissue was homogenized, digested, and analyzed for mercury in accordance with USEPA Method 245.6 which must be used to construct human health based fish consumption advisories. Mean mercury concentrations were (x ±SD) 0.089±0.065 ppm, 0.154±0.127 ppm, and 0.098±0.080 ppm in largemouth bass, striped bass, and channel catfish, respectively. An analysis of covariance (ANCOVA) indicated a significant difference between mercury concentrations among the three species (F 2,208 = 22.448, p< 0.001). Contrasts revealed that each species differed significantly from each other (p<0.050).

There was a significant overall difference in mean mercury concentration between fish from the four major basins of Lake Mead (F3,208 = 20.541, p<0.001). The mean mercury concentration in Boulder Basin was significantly lower than that of Gregg Basin (p<0.001), Virgin Basin (p<0.001), and Overton Arm (p<0.001). Out of 221 samples analyzed, 2 samples (both striped bass) were found to have mean mercury concentrations above the Environmental Protection Agency's action level of 0.5 ppm. There were no samples found containing concentrations above the Food and Drug Administration's maximum allowable mercury concentration in fish and food products (1.0 ppm).

Keywords

Environmental health--Toxicology; Fishes--Mercury content; Mercury--Environmental aspects; Mercury--Toxicology; Methylmercury

Disciplines

Environmental Public Health | Pharmacology, Toxicology and Environmental Health | Public Health

Language

English

Comments

Signatures have been redacted for privacy and security measures.


Share

COinS