Normal range of human red blood cell acetylcholinesterase activity.

The normal range of human erythrocyte acetylcholinesterase (RBC-AChE) activity is important when monitoring exposure to pesticides and chemical warfare agents. A modification of Michel's method measured RBC-AChE activities from 991 individuals (818 males and 173 females) presumably unexposed to nerve agents. Median age was 42 (range, 18-76) years. RBC-AChE (mean +/- SD) was 0.74 +/- 0.06 delta pH units/hour. Multivariate linear regression showed an association with age (slope +0.0008 delta pH units/hour for each year; P < 0.001) unlikely to be clinically significant. The findings represent the largest study of human RBC-AChE to date providing measures of central tendency and variation.

Polycyclic aromatic hydrocarbon exposure in Steller's eiders (Polysticta stelleri) and Harlequin ducks (Histronicus histronicus) in the eastern Aleutian Islands, Alaska, USA.

Seaducks may be affected by harmful levels of polycyclic aromatic hydrocarbons (PAHs) at seaports near the Arctic. As an indicator of exposure to PAHs, we measured hepatic enzyme 7-ethoxyresorufin-O-deethylase activity (EROD) to determine cytochrome P4501A induction in Steller's eiders (Polysticta stelleri) and Harlequin ducks (Histronicus histronicus) from Unalaska, Popof, and Unga Islands (AK, USA) in 2002 and 2003. We measured PAHs and organic contaminants in seaduck prey samples and polychlorinated biphenyl congeners in seaduck blood plasma to determine any relationship to EROD. Using Akaike's information criterion, species and site differences best explained EROD patterns: Activity was higher in Harlequin ducks than in Steller's eiders and higher at industrial than at nonindustrial sites. Site-specific concentrations of PAHs in blue mussels ([Mytilus trossilus] seaduck prey; PAH concentrations higher at Dutch Harbor, Unalaska, than at other sites) also was important in defining EROD patterns. Organochlorine compounds rarely were detected in prey samples. No relationship was found between polychlorinated biphenyl congeners in avian blood and EROD, which further supported inferences derived from Akaike's information criterion. Congeners were highest in seaducks from a nonindustrial or reference site, contrary to PAH patterns. To assist in interpreting the field study, 15 captive Steller's eiders were dosed with a PAH known to induce cytochrome P4501A. Dosed, captive Steller's eiders had definitive induction, but results indicated that wild Steller's eiders were exposed to PAHs or other inducing compounds at levels greater than those used in laboratory studies. Concentrations of PAHs in blue mussels at or near Dutch Harbor (approximately 1,180-5,980 ng/g) approached those found at highly contaminated sites (approximately 4,100-7,500 ng/g).

Monitoring cholinesterases to detect pesticide exposure.

Progress toward a standard blood cholinesterase assay to assess pesticide exposures in the agricultural workplace and to identify possible victims of chemical warfare agents is discussed. Examples given are drawn from collaborations with clinical laboratories in California and the Department of Defense Cholinesterase Reference Laboratory (CRL).

Meeting requirements of the California cholinesterase monitoring program.

California (CA) has a long-standing formal blood cholinesterase (ChE) monitoring program for mixers, loaders, and applicators of pesticides. When the authors found commercial clinical kits were not optimal for assaying blood ChEs, CA regulations were revised to specify use of the Ellman ChE assay or to demonstrate a conversion factor with a correlation (r(2)) of 0.9 or better. The authors were enlisted to work with the clinical laboratories. Only two of seven participating laboratories generated an acceptable correlation for red blood cells (RBCs), whereas four of five laboratories had an acceptable correlation for plasma ChE. Subsequently, the CA Department of Pesticide Regulation (DPR) restated the need to meet this requirement and the authors worked with several of the clinical laboratories using a bovine ghost RBC ChE as a reference. Unfortunately, only 3 of 10 laboratories had acceptable correlations. Next, the authors provided all interested laboratories with human blood and plasma samples to perform the comparison study outlined in the regulation (Section 6728f). Fourteen laboratories participated; 9 met the ChE criteria for whole blood, 14 for plasma, and 6 for RBCs. Based on such data, on July 8, 2003, DPR notified the CA Agricultural Commissioners that nine of the participating laboratories were approved for ChE testing. Later work resulted in acceptable RBC values for two of the laboratories and their approval. The authors continue to work with laboratories interested in being on the approved list. The current list may be seen at www.cdpr.ca.gov/docs/whs/lablist.htm.

Aryl hydrocarbon receptor-mediated activity of particulate organic matter from the Paso del Norte airshed along the U.S.-Mexico border.

In this study, we determined the biologic activity of dichloromethane-extracted particulate matter < 10 micro m in aerodynamic diameter (PM10) obtained from filters at three sites in the Paso del Norte airshed, which includes El Paso, Texas, USA; Juarez, Chihuahua, Mexico, and Sunland Park, New Mexico, USA. The extracts were rich in polycyclic aromatic hydrocarbons (PAHs) and had significant biologic activity, measured using two in vitro assay systems: ethoxyresorufin-(O-deethylase (EROD) induction and the aryl hydrocarbon-receptor luciferase reporter system. In most cases, both EROD (5.25 pmol/min/mg protein) and luciferase activities (994 relative light units/mg) were highest in extracts from the Advance site located in an industrial neighborhood in Juarez. These values represented 58% and 55%, respectively, of induction associated with 1 micro M ss-naphthoflavone exposures. In contrast, little activity was observed at the Northeast Clinic site in El Paso, the reference site. In most cases, luciferase and EROD activity from extracts collected from the Tillman Health Center site, situated in downtown El Paso, fell between those observed at the other two sites. Overall, a statistically significant correlation existed between PM10 and EROD and luciferase activities. Chemical analysis of extracts collected from the Advance site demonstrated that concentrations of most PAHs were higher than those reported in most other metropolitan areas in the United States. Calculations made with these data suggest a cancer risk of 5-12 cases per 100,000 people. This risk estimate, as well as comparisons with the work of other investigators, raises concern regarding the potential for adverse health effects to the residents of this airshed. Further work is needed to understand the sources, exposure, and effects of PM10 and particulate organic material in the Paso del Norte airshed.