Health hazard evaluation report: HETA-99-0091-2846, McCain Foods, Inc., Plover, Wisconsin.
On January 29, 1999, the National Institute for Occupational Safety and Health (NIOSH) received a confidential employee request for a Health Hazard Evaluation (HHE) at the Plover, Wisconsin, facility of McCain Foods, Inc., a plant which produces frozen potato products. The requesters expressed concern regarding possible health effects, especially respiratory problems, which they believed were associated with exposures to carbon monoxide (CO), chlorine gas (Cl2), and unknown chemicals. On March 30, 1999, a preliminary NIOSH investigation focused on the potential for Cl2, and CO exposures. Screening tests for the presence of both chemicals in air were negative. However, informal worker interviews suggested that health problems might be widespread. During a July 25-26, 1999, site visit, NIOSH researchers investigated whether the health effects were related to bioaerosols, such as bacteria, fungi, or their products (especially endotoxins, which are components of the coats of Gram-negative bacteria). A questionnaire survey of workers was conducted to determine the frequency of respiratory and other health symptoms and full-shift, personal breathing zone (PBZ) samples were collected to estimate time-weighted average (TWA) concentrations of airborne particulates and endotoxin. Data was categorized by whether it was collected in the potato processing areas or in the packaging areas of the plant. The questionnaire survey of 115 of 185 workers found the prevalence of chest tightness was more than 2.5 times greater in the processing workers than the packaging workers (39% versus 14%, prevalence rate [PR] = 2.8, 95% confidence interval [CI]: 1.36-5.75). Processing employees also had twice the prevalence of shortness of breath (43% versus 18%, PR = 2.4, 95% CI: 1.29-4.63), twice the prevalence of pneumonia or chest flu episodes (48% versus 25%, PR = 2.0, 95% CI: 1.16-3.33) , and one and one-half times the prevalence of eye, nose, or throat irritation (55% versus 33%, PR = 1.7, 95% CI: 1.07-2.57) compared to packaging employees. These findings remained statistically significant after controlling for the confounding factors of age and cigarette smoking. Airborne endotoxin concentrations in the processing area greatly exceeded those in the packaging area. PBZ endotoxin concentrations in the processing area of the plant averaged 168 endotoxin units per cubic meter (EU/m3), but those in the packaging area were less than the lower limit of detection (0.018 EU/m3). A likely source of bacteria, and, therefore, endotoxins, is a wastewater gutter system located throughout the processing area of the plant. The higher rates of respiratory symptoms in production employees and the higher levels of endotoxin in the production area compared to packaging are consistent with an association between those symptoms and endotoxin exposures at the Plover facility. However, a causal association cannot conclusively be established because of the cross-sectional nature of the study. Our results are consistent with those reported in published studies of other potato processing plants, some of which demonstrated high endotoxin levels associated with health effects. Exposures to endotoxins should be reduced to the extent feasible by instituting engineering controls designed to prevent aerosolization of wastewater from the gutter system. Maintenance and cleaning procedures on the gutter system should be improved, thereby reducing the potential for bacterial growth in the wastewater. Workers' health should be monitored, and workers with endotoxin-related health problems should be offered reassignment to areas where endotoxin exposures are lower.