Assessment of blood-splash exposures of medical-waste treatment workers.

Introduction

The authors estimate that more than 10,000 U.S. workers are involved in processing medical waste on site at health care establishments and off site at commercial treatment facilities. In 1994 it was estimated that more than 3.5 million tons of medical wastes were generated in the United States each year (1). State regulations requiring the treatment of potentially infectious and otherwise hazardous medical wastes have increased waste handling and the corresponding risks to worker health and safety. Workers who routinely collect, transport, treat, and dispose of untreated, regulated medical waste risk exposure to bloodborne pathogens from direct contact with blood or other body fluids on contaminated surfaces; from spills or splashes onto cuts, abrasions, eyes, and mucous membranes; and from accidental puncture wounds caused by needles, scalpels, or glass. The OSHA Bloodborne Pathogens Standard applies to these workers and seeks to eliminate or minimize occupational exposure to blood or other body fluids that may contain hepatitis B virus (HBV), human immunodeficiency virus (HIV), hepatitis C virus (HCV), and other bloodborne pathogens (2).

In recent years, the authors have observed workers at various medical-waste treatment facilities handling wastes that leaked blood and residual fluids and caused visible blood splashes. At the three facilities visited for this study, most blood and fluid splashes occurred when small tubs (32 gallons or less) of biohazardous wastes were manually dumped into larger containers for processing with various treatment technologies.

For a 1990 study, waste industry workers were surveyed about occupational exposure to infectious waste. Fifty percent of the respondents reported receiving cuts and scratches, 32 percent reported direct contact with waste blood on clothing or shoes, and five percent reported direct contact with blood on the face or eyes (3). Infectious agents such as HCV and HIV have been shown to be transmitted by, respectively, blood splash to the conjunctiva and mucosal exposure (4, 5). These accounts indicated a need to assess the potential for worker exposure to bloodborne pathogens from blood splashes to the body as well as from surfaces in the work areas.

Three off-site, commercial medical-waste treatment facilities from across the United States participated in the study. All relied heavily on the manual dumping of wastes from small containers (32 gallons or less) onto conveyors or into larger containers preparatory to treatment and final disposal. The number of personnel performing this task varied from two to five per shift. The number of shifts in 24 hours ranged from one to three. Likewise, the amount of medical-waste throughput varied, reaching more than 50 tons per day at the facility working around the clock.

Methods

Three studies from the technical literature discuss sampling and detecting blood aerosols from surgical and dental procedures by eluting a filter collection medium in water and testing for the presence of hemoglobin with [TABULAR DATA FOR TABLE 1 OMITTED] [TABULAR DATA FOR TABLE 2 OMITTED] commercially available Hemastix[R] urinalysis test strips (Miles, Inc., Elkhart, Indiana) (6-8). From this literature, different sampling methods were derived to assess blood contamination on workers and on surfaces at each of the medical-waste treatment facilities. Specifically manufactured, 4-by-4-inch sample holders, which had been developed by NIOSH to monitor herbicide exposures of farm workers, were adapted to hold cotton pads. The pads were attached to workers' clothing to monitor for blood splashes on their torsos. Also, personal protective equipment (PPE) and treatment system surfaces with which workers could come into contact were monitored for blood-splash contamination with sterile cotton wipes. The pads and wipes were eluted in 25 milliliters (mL) of sterile buffer and were tested for blood with the Hemastix method. All sampling procedures were performed with sterile gloves to protect the investigators.

Prior to field use of the Hemastix method, laboratory testing was conducted to determine hemoglobin detection limits and suitable blood collection and elution media. As shown in Table 1, serial 10-fold dilutions from 1:10 through 1:10,000,000 of defibrinated sheep blood were made with sterile, commercially available FTA Hemagglutination Buffer (FTAB). The dilution detection limit was 1:1,000,000. The Hemastix literature reports a detection limit of five to 20 red blood cells (RBC) per microliter of fluid, which converts to a minimum of 5 X [10.sup.3] RBC per milliliter [TABULAR DATA FOR TABLE 3 OMITTED] of fluid (assuming five RBC per microliter). To translate the detection limit found experimentally into RBC per milliliter, the authors assumed an average concentration of 1 X [10.sup.9] RBC per milliliter of human blood (9). The detection limit concentration of 1:1,000,000 was thus determined to be 1 X [10.sup.3] RBC/mL, which was slightly lower than the detection limit reported by the Hemastix manufacturer. This demonstrated a very sensitive test for detecting blood splashes.

TABLE 4

Summary of Blood Splashes on Process Area Surfaces at Two Medical-Waste
Treatment Facilities

Facility    Surface Wipe   Surfaces that Tested    Percentage of
           Samples Taken    Positive for Blood    Positive Samples

1               45                  23                   51
2               51                  38                   74

Total           96                  61                   64

The three methods used to assess worker exposure to blood splashes are outlined below. Blood splashes on workers' clothing were assessed in all three facilities; blood splashes on PPE and work surfaces were assessed in two facilities. Types and extent of PPE varied among workers at the different facilities. Workers wore either face shields or goggles, but never both.

Blood Splashes on Clothing

This personal monitoring required the use of previously developed, specially manufactured, 4-by-4-inch sample holders. The holders were loaded with clean, 4-by-4-inch cotton pads. Six pads were attached to each worker: four on the front and two on the back of the upper torso. Workers were monitored by shift. Before each shift, the pads were assembled in the required numbers and attached to the same relative locations of the upper body on up to five workers (see photos on page 9). Each pad was labeled according to location on the worker. At the end of each shift, pads were visually assessed for blood splashes, and the numbers and sizes of splashes were recorded. All pads (with and without visible blood) were then eluted in 25 mL of sterile buffer and tested for hemoglobin as described below.

Blood Splashes on Personal Eye Protectors (PEP)

Prior to a shift, the PEP (i.e., face shields or goggles) for up to five workers were cleaned according to facility protocol. Next, the PEP were wiped with a 4-by-4-inch clean cotton pad wetted with sterile buffer. The pads were eluted (with vigorous shaking for 30 seconds) in 25 mL of sterile buffer and tested with Hemastix. The PEP were then issued to the workers. After each shift, the PEP were visually inspected. Researchers noted the number of visible blood and fluid splashes and their approximate sizes. Next, the PEP were wiped with a 4-by-4-inch clean cotton pad wetted with sterile buffer (see photo at left, below), and tested for hemoglobin, as described.

Blood Splashes on Surfaces

Researchers identified potentially blood-contaminated surfaces with which workers could come into direct contact in the process area. These surfaces included, but were not limited to, instrument control panels, guard railings, waste containers, waste-prodding devices, and telephones. Again, environmental work surfaces were wiped with 4-by-4-inch sterile cotton pads, which were then tested for hemoglobin as previously described (see photo at right, below).

Results

The two photographs on page 11 show typical visible blood splashes found on pads on workers' torsos and on PEP. Positive blood splashes on the pads were documented in all three of the monitored facilities (Table 2). Consistently, about eight percent of the pads tested positive for hemoglobin in each facility. In two facilities, personal eye goggles or face protection shields were monitored for blood splashes for a total of 18 workers. Positive hemoglobin results were found for a total of four out of the 18 eye protection shields (22 percent) (Table 3). Positive hemoglobin results were found on various surfaces in each processing area of the facilities tested. Of 96 surfaces tested in two of the facilities, 64 percent were found to be positive for hemoglobin (Table 4). On each day of testing, negative controls included patches worn by office workers at each facility, positive blood controls were used to verify reagent reactivity, and unused pads (data not shown) served as field blanks. All pads worn by office workers tested negative for hemoglobin.

Conclusions

This study assessed blood-splash exposures of medical-waste treatment workers involved in the manual dumping of regulated medical waste. Results of the study demonstrated that blood splashes present a significant health risk. Blood splashes were detected visually and by hemoglobin testing of cotton pads attached to clothing. In addition, wipes were taken from face shields and a variety of process and facility work surfaces. This demonstration of blood-splash exposures indicates the importance of worker training, immunization, use of personal protective equipment, and personal hygiene. It is strongly recommended that engineering controls be used to minimize or eliminate the manual dumping of regulated medical waste whenever possible.

Adherence to all requirements of the Bloodborne Pathogens Standard is important, and management should enforce the use of proper protective clothing and eye and face shields.

During this study, workers were observed wearing either face shields (secondary protection) with no goggles or goggles (primary protection) with no face shields. Primary eye protectors must be mandatory. ANSI Standard Z87.1-1989 ("Practice for Occupational and Educational Eye and Face Protection") states that "face shields are secondary protectors and shall be used only with primary protectors." The authors also recommend that all workers who have direct contact with untreated medical waste be provided with clean sets of protective clothing daily. The clothing should be removed at the facility and remain there following the work shift. Potentially contaminated safety footwear also should remain at the facility to further reduce the potential for transmission of infectious agents to the home environment.

Acknowledgements: This study was supported by a CDC/NIOSH contract (contract number 200-95-2960) to the Research Triangle Institute, Research Triangle Park, North Carolina. The assistance and cooperation of the management and the workers at the participating facilities are greatly appreciated.

Corresponding Author: Keith Leese, Environmental Scientist, DynCorp Health Research Services, 4815 Emperor Boulevard, Suite 300, Durham, NC 27703.

REFERENCES

1. Air and Waste Management Medical Waste Committee (1994), "Medical Waste Disposal," Journal of Air and Waste Management Association, 44:1176-1179.

2. "Occupational Exposures to Bloodborne Pathogens: Final Rule," Federal Register, 56(235). 29 CFR 1910.1030.

3. Turnberg, W.L., and F. Frost (1990), "Survey of Occupational Exposure of Waste Industry Workers to Infectious Waste in Washington State," American Journal of Public Health, 80(10):1262-1264.

4. Sartori, M., M. Aglietta, G. La Terra, A. Manzin, C. Navino, and G. Verzetti (1993), "Transmission of Hepatitis C via Blood Splash into Conjunctiva," Scandinavian Journal of Infectious Disease, 25:270-271.

5. Henderson, D.K. (1995), Principles and Practice of Infectious Diseases, 4th ed., New York: Churchill Livingstone.

6. Heinsohn, P., L. Balzor, C.H. Bennett, D.L. Jewett, A. Rosen, and P. Seipel (1991), "Aerosols Created by Some Surgical Power Tools: Particle Size Distribution and Qualitative Hemoglobin Content," Applied Occupational and Environmental Hygiene, 6:773-776.

7. Jewett, D.L., C. Bennett, P. Heinsohn, C. Nevilly, and A. Rosen (1992), "Blood-Containing Aerosols Generated by Surgical Techniques: A Possible Infection Hazard," American Industrial Hygiene Association Journal, 53(4):228-231.

8. Miller, R.L. (1995), "Characteristics of Blood-Containing Aerosols Generated by Common Powered Dental Instruments," American Industrial Hygiene Association Journal, 56:670-676.

9. Leavell, B. S., and O. A. Thorup, Jr. (1966), Fundamentals of Clinical Hematology, Philadelphia: W.B. Saunders Company.