Occupational exposure of workers to 1,3-butadiene.

Researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted an extent-of-exposure study of the 1,3-butadiene monomer, polymer, and end-user industries to determine the size of the exposed workforce, evaluate control technologies and personal protective equipment programs, and assess occupational exposure to 1,3-butadiene. A new analytical method was developed for 1,3-butadiene that increased the sensitivity and selectivity of the previous NIOSH method. The new method is sensitive to 0.2 microgram per 1,3-butadiene sample. Walk-through surveys were conducted in 11 monomer, 17 polymer, and 2 end-user plants. In-depth industrial hygiene surveys were conducted at 4 monomer, 5 polymer, and 2 end-user plants. Airborne exposure concentrations of 1,3-butadiene were determined using personal sampling for each job category. A total of 692 full shift and short-term personnel and 259 area air samples were examined for the presence of 1,3-butadiene. Sample results indicated that all worker exposures were well below the current OSHA PEL of 1000 ppm. Exposures ranged from less than 0.006 ppm to 374 ppm. The average exposure for all samples was less than 2 ppm. The present American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value for 1,3-butadiene is 10 ppm. To reduce the potential for occupational exposure, it is recommended that quality control sampling be conducted using a closed loop system. Also all process pumps should be retrofitted with dual mechanical seals, magnetic gauges should be used in loading and unloading rail cars, and engineering controls should be designed for safely voiding quality control cylinders.

Industrial hygiene and control technology assessment of ion implantation operations.

Ion implantation is a process used to create the functional units (pn junctions) of integrated circuits, photovoltaic (solar) cells and other semiconductor devices. During the process, ions of an impurity or a "dopant" material are created, accelerated and imbedded in wafers of silicon. Workers responsible for implantation equipment are believed to be at risk from exposure to both chemical (dopant compounds) and physical (ionizing radiation) agents. In an effort to characterize the chemical exposures, monitoring for chemical hazards was conducted near eleven ion implanters at three integrated circuit facilities, while ionizing radiation was monitored near four of these units at two of the facilities. The workplace monitoring suggests that ion implantation operators routinely are exposed to low-level concentrations of dopants. Although the exact nature of dopant compounds released to the work environment was not determined, area and personal samples taken during normal operating activities found concentrations of arsenic, boron and phosphorous below OSHA Permissible Exposure Limits (PELs) for related compounds; area samples collected during implanter maintenance activities suggest that a potential exists for more serious exposures. The results of badge dosimetry monitoring for ionizing radiation indicate that serious exposures are unlikely to occur while engineering controls remain intact. All emissions were detected at levels unlikely to result in exposures above the OSHA standard for the whole body (1.25 rems per calendar quarter). The success of existing controls in preventing worker exposures is discussed. Particular emphasis is given to the differential exposures likely to be experienced by operators and maintenance personnel.(ABSTRACT TRUNCATED AT 250 WORDS)

Release of arsenic from semiconductor wafers.

The production of integrated circuits and other semiconductor devices requires the introduction of impurities or dopants into the crystal lattice of a silicon substrate. This "doping" or junction formation is achieved through one of two processes: thermal diffusion or ion implantation. Ion implantation, the more contemporary and more accurate of the two processes, accomplishes junction formation by bombarding selected areas of the silicon wafer with a beam of dopant ions. Inorganic arsenic, which is regulated by the Occupational Health and Safety Administration (OSHA) as a carcinogen, is frequently used as dopant material. Silicon wafers are found to emit inorganic arsenic following ion implantation. Data collected during this experiment demonstrate that arsenic is released over a 3.5-hour period following implantation and that the total amount of arsenic emitted may approach 6.0 micrograms per 100 wafers processed within 4 hours after implantation. The discovery and quantification of this phenomenon suggest that newly implanted silicon wafers are a potential source of arsenic contamination--a source that may impact both the quality of the work environment and the integrated circuit product.

Methodology for an occupational risk assessment: an evaluation of four processes for the fabrication of photovoltaic cells.

Determining occupational health and safety risks posed by emerging technologies is difficult because of limited statistics. Nevertheless, estimates of such risks must be constructed to permit comparison of various technologies to identify the most attractive processes. One way to estimate risks is to use statistics on related industries. Based on process labor requirements and associated occupational health data, risks to workers and to society posed by an emerging technology can be calculated. Using data from the California semiconductor industry, this study applies a five-step occupational risk assessment procedure to four processes for the fabrication of photovoltaic cells. The validity of the occupational risk assessment method is discussed.