Evaluation of Airborne Carbon Monoxide Exposure Monitoring Program in Produce Cooler Operations (Palm Beach County, Florida)

Article excerpt

Carbon monoxide (CO), a colorless and odorless gas, is classified as a pulmonary asphyxiant. High level exposures can cause toxic effects or death in humans and animals (1); CO poisoning reportedly is responsible for as many as 4,000 deaths per year in the United States (2). Even low-level CO exposures can have cardiovascular, neurobehavioral, and fetotoxic effects. Smoking one pack of cigarettes a day is enough to raise carboxyhemoglobin (COHb) levels in the blood sufficiently to cause subclinical cardiovascular and neurobehavioral effects (3).

CO poisonings have been associated with the use of propane-powered lift trucks. Treated for acute CO poisoning at the F.G. Hail Hypo-Hyperbaric Environmental at Duke University Medical Center, 17 patients were found to have been exposed to CO from the exhaust of propane-fueled forklifts used in enclosed warehouses (4).

In Southern Florida, due to the warm climate, warehouses tend to be well ventilated by keeping bay doors open and running fans for the comfort of the staff. However, ventilation is not feasible in operations requiring cold storage, so there is a higher risk of exhaust build-up if propane lift trucks are used in these areas. Recently, CO poisonings occurred at a South Florida shipping operation when a propane lift truck was used instead of a hand lift in a small candy cooler (5).

Given the increased risk of CO exposure, and resulting morbidity and possible mortality, the Palm Beach County Public Health Unit, Division of Environmental Health instituted a CO monitoring program for produce cooler operations in western Palm Beach County. The purpose of this study was to evaluate the effectiveness of this program for decreasing the CO exposure from propane lift truck exhaust for the population of workers entering these produce coolers during the spring corn season. The evaluation recorded the employees' carbon monoxide exposure levels before and after intervention, measured the success of various exposure reduction strategies, and made recommendations to reduce or eliminate future risk. The success of this program and the effectiveness of various environmental control methods was demonstrated.

There were seven produce cooler operations identified in western Palm, Beach County that used propane lift trucks in coolers at the beginning of the study in 1991. Monitoring was performed annually during the heaviest spring corn harvest. Following arrival and pre-cooling, corn was loaded into the coolers with lift trucks. After storage, corn was removed and placed in refrigerated tractor-trailers.


The population studied was employees that at some point during an 8-hour shift entered the produce cooler(s). Blood testing would have been invasive and could reflect CO exposures from tobacco smoke and sources outside the workplace; therefore, the COHb (6) method was not chosen to evaluate occupational CO exposure from propane lift truck exhaust. CO levels in air were monitored using personal monitoring, grab sampling, and area sampling techniques. Personal monitoring and area sampling were performed using Gastec Passive Dosi-tubes to yield TWA CO levels over 8-hour workshifts. A CEA Model CO-7 CO detector was used to determine various grab sample CO levels. The U.S. Department of Labor, Occupational Safety and Health Administration (OSHA), 29 Code of Federal Regulations part 1910.000(a), Table Z-1-A, Permissible Exposure Level (PEL) was 35 parts per million (ppm) CO as an airborne exposure in any 8-hour shift of a 40-hour work week. The ceiling limit not to be exceeded at any time was 200 ppm. (Both of these personal exposure levels were revoked and ceased to be enforced by OSHA the last year of the three-year study. The current OSHA PEL of 50 ppm CO as a TWA was not used. There is currently no OSHA ceiling limit for CO.)

Five of the produce cooler operations needed interventions to reduce CO exposure. Each company was allowed to choose which one or combination of interventions to implement. …