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PubMed1988

Assessment of the developmental risks resulting from occupational exposure to select glycol ethers within the semiconductor industry.

This risk assessment evaluates the potential human hazards of adverse developmental effects posed by exposure to 2-ethoxyethanol (2-EE), 2-ethoxyethanol acetate (2-EEA), 2-methoxyethanol (2-ME), and 2-methoxyethanol acetate (2-MEA) as they are currently used in semiconductor manufacturing. These glycol ethers are contained in positive photoresists used in the wafer fabrication process. The available data on the developmental toxicology of these glycol ethers indicates that each can selectively affect the offspring of pregnant animals that have been exposed to relatively low vapor concentrations. For these chemicals, the ratio of the lowest dose which adversely affected the pregnant animals (A) and the lowest dose which produced developmental effects in offspring (D), e.g., A/D ranged from 1-5. Approximately 400 workplace air samples of 4-8 h duration, both personal and area, from seven different companies were used to assess the degree of inhalation exposure during the manufacture of wafers. The geometric mean results obtained during personal sampling of workplace air for 2-EE, 2-EEA, 2-ME, and 2-MEA were 0.36, 0.02, 0.10, and 0.01 ppm, respectively. These levels are 14- to 500-fold lower than the applicable threshold limit value (TLV) currently recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). Specifically, the margins of safety between the typical occupational exposure and the TLV for 2-ME, 2-EE, 2-MEA, and 2-EEA are 50, 14, 500, and 250, respectively. The TLVs for these chemicals were set at levels considered sufficiently low to protect workers and their offspring from adverse effects and are about 2- to 10-fold lower than the various no-observed-effect levels (NOELs) obtained in animal tests. Based on more recent data, lower TLVs are indicated. The safety-factor approach, rather than mathematical models developed for estimating cancer risks, was used in this analysis. Historical data have shown that the application of safety factors of 10-100 to the NOEL, as determined in Segment II developmental toxicology tests in animals, should be adequate to protect humans. In its risk assessment guidelines, the U.S. Environmental Protection Agency (EPA) selected the uncertainty-factor approach as the most reasonable one for evaluating the hazards of developmental toxicants. This assessment indicates that the airborne concentrations of these glycol ethers in the semiconductor industry are, in general, sufficiently low to protect employees against their adverse developmental and reproductive effects as well as any other toxic effects as long as dermal exposure is minimal.

Air Pollutants, Occupational↗
PubMedDate not supplied

Personal monitoring instrument for the selective measurement of multiple organic vapors.

Development and laboratory testing of a small instrument capable of recognizing and quantifying multiple organic vapors at low- and sub-ppm concentrations is described. The instrument is slightly larger than a standard personal sampling pump and employs an array of three polymer-coated surface-acoustic-wave microsensors for vapor detection. Vapors are first trapped on a miniature adsorbent preconcentrator housed within the instrument and then thermally desorbed for analysis by the microsensor array. Each measurement cycle requires 5.5 min. The collective responses from the array are stored and then analyzed using pattern recognition methods to yield the identities and concentrations of collected vapors and vapor mixture components. Following initial optimization of instrument operating parameters, calibrations were performed with 16 organic solvent vapors and selected mixtures to establish a response library for each of two identical instruments. Limits of detection < or = 0.1 x threshold limit value were obtained for most vapors. In a series of 90 subsequent exposure tests, vapors were recognized with an error of < 6% (individual vapor challenges) and < 16% (binary mixture challenges) and quantified with an average error of < 10%. Monte Carlo simulations were coupled with pattern recognition analyses to predict the performance for many possible vapor mixtures and sensor combinations. Predicted recognition errors ranged from < 1 to 24%. Performance is shown to depend significantly on the interfacial polymer layers deposited on the sensors in the array and the nature and complexity of the vapor mixtures being analyzed. Results establish the capability of this technology to provide selective multivapor monitoring of personal exposures in workplace environments.

Adsorption↗
PubMedDate not supplied

Field evaluation of a portable photoionization detector for assessing exposure to solvent mixtures.

To evaluate a portable photoionization detector for assessing personal exposure to solvent mixtures, a set of 26 side-by-side, time-weighted average (TWA) personal breathing zone samples were collected during various construction painting tasks by two different sampling methods: (1) standard charcoal sorbent tubes analyzed by gas chromatography (CST/GC), and (2) a direct-reading photoionization detector coupled with an extended data-logger (PID). The TWA concentrations of the hydrocarbons detected by CST/GC analysis were summed for comparison with the TWA concentration obtained from the direct-reading PID. Based on linear regression between the log TWA concentrations of the two sampling methods, the data were highly correlated (r2 = 0.95). Since the solvents had effects that may be considered additive, threshold limit values (TLVs) for mixtures were developed using American Conference of Governmental Industrial Hygienists formulas to evaluate solvent exposure. The logs of the TLV mixture data from the sampling methods were highly correlated (r2 = 0.94). Based on the linear regression analyses, the response of the portable PID was highly correlated to the CST/GC results for hydrocarbon mixtures encountered during various painting tasks. Due to the short duration of tasks, highly fluctuating exposures, and complexity of the mixtures, the PID may provide the most cost-effective, detailed exposure assessment for solvent mixtures.

Air Pollutants, Occupational↗
PubMedDate not supplied

Hydrocarbon solvent exposure data: compilation and analysis of the literature.

An occupational exposure database for hydrocarbon solvent end-use applications was constructed from the published literature. The database provides exposure assessment information for such purposes as regulatory risk assessments, support of industry product stewardship initiatives, and identification of applications in which limited exposure data are available. It is quantitative, documented, and based on credible data. Approximately 350 articles containing quantitative hydrocarbon solvent exposure data were identified using a search of computer databases of published literature. Many articles did not report sufficient details of the exposure data for inclusion in the database (e.g., full-shift exposure or task-based exposure data). Others were excluded because only limited summary statistics were provided, which precluded statistical analysis of the data (e.g., arithmetic mean concentration presented, but no sample number). Following evaluation, 16,880 hydrocarbon solvent exposure measurements from 99 articles were entered into a database for analysis. Methods used to identify and evaluate published solvent exposure data are described along with more detailed analysis of worker exposure to hydrocarbon solvents in three major end-use applications: painting and coating, printing, and adhesives. Solvent exposures were evaluated against current ACGIH threshold limit values (TLVs) and trends were identified. Limited quantitative data are available prior to 1970. In general, reported hydrocarbon solvent exposures decreased fourfold from 1960 to 1998, were below the TLVs applicable to specific hydrocarbon solvents at the time, and on average have been below 40% of the TLV since 1980. The database already has proved valuable; however, the utility of published exposure data could be further improved if authors consistently reported essential data elements and supporting information.

Adhesives↗
PubMedDate not supplied

Dermal absorption of neat liquid solvents on brief exposures in volunteers.

The dermal absorption of liquid 1,1,1-trichloroethane (111TRI), trichloroethene (TRI), tetrachloroethene (TETRA), toluene (TOL), and m-xylene (XYL) was studied in volunteers. The solvents were applied for 3 min on the volar forearm over an area of 27 cm2. An inhalation exposure with a known input rate served as a reference exposure. Using the linear system dynamics method, permeation rates were calculated from exhaled air concentration courses measured after both inhalation and dermal exposure. The permeation time courses of the solvents showed two different patterns. TRI, TOL, and 111TRI in three subjects showed fast increase in permeation, reaching maximal permeation rates a few minutes after initiation of exposure. Slower permeation was seen in the other three subjects exposed to 111TRI and in all subjects exposed to TETRA and XYL with the time of maximal permeation rates of 15-25 min. These differences in the permeation may partly be explained by the irritation of the skin observed in all subjects showing fast permeation kinetics. The flux into the skin averaged over the exposure period amounted to 56, 430, 69, 223, and 46 nmol/cm2/min for 111TRI, TRI, TETRA, TOL, and XYL, respectively. Comparing the dermal uptake with the respiratory uptake at the TLV, all solvents showed substantial skin absorption, although at present only TOL has a skin indication in the American Conference of Governmental Industrial Hygienists threshold limit value list.

Adult↗
PubMed1979

Simultaneous determination of polar and non-polar solvents in air using a two-phase desorption from charcoal.

A gas chromatographic procedure is described which is capable of measuring both polar and non-polar organic solvents present simultaneously in the work environment at concentrations between 1/100 and 1 times the Threshold Limit Values (TLV). Airborne organics are collected on a single activated charcoal tube for periods of 3 to 6 hours and desorbed with a two-phase (water/carbon disulfide) desorption mixture. Organic and aqueous phases are analyzed separately on the same gas chromatographic column packed with Oronite NIW on Carbopack B. Recoveries were determined for fifteen common solvents. Most recoveries were greater than 90% with all coefficients of variation being less than +/- 10%. Breakthrough was observed only when solvents were present at very high concentrations. Examples of field sampling are also presented. This procedure is generally applicable for monitoring complex mixtures of volatile organic compounds in air. Advantages include excellent recoveries for polar solvents such as acetone and ethanol, utilization of common analytical instrumentation under a single set of operating conditions and compatibility with TWA personnel monitoring methodology.

Air↗
PubMed1981

Concentrations and health effects of potash dust.

In an investigation of the relationship between atmospheric dust levels and worker health, the respiratory dust exposures of employees at two Saskatchewan potash mines were examined following atmospheric measurements. Some, notably those of the mining crew and the screening operators, were above the Threshold Limit Value 8-hour Time Weighted Average (TLV-TWA) for total nuisance particulates specified by the American Conference of Governmental Industrial Hygienists (ACGIH). Respiratory symptoms were recorded and forced expiratory lung function tests were done among 850 volunteers drawn from an eligible work force of 931. The results were compared between low and higher exposure groups after allowing for personal factors such as age and smoking habits. Symptoms of Grade I chronic phlegm production and mild shortness of breath and chronic cough were more common in the higher exposure groups, but episodes of chest illness were not. Severe respiratory symptoms were rare. There were no statistically significant differences in the proportions performing lung function tests below predicted values.

Air Pollutants↗
PubMed1982

Blood as a matrix for biological monitoring.

Traditionally, air sampling and analyses have been used to determine a worker's exposure to various airborne contaminants. Airborne Threshold Limit Values and permissible exposure levels have been developed for many contaminants. In certain situations, however, measurements of airborne concentrations are not always a reliable index of employee exposure. The determination of a chemical agent or its metabolite in a biological medium such as blood may provide more accurate information on exposure and the effects of exposure to hazardous substances. Perhaps the most common application for biological monitoring has been the determination of lead in blood. Analytical techniques have been developed for an additional parameter, zinc protoporphyrin, which, together with the blood-lead level, can give a more complete picture of lead absorption and metabolism. Information on blood-lead and zinc protoporphyrin monitoring as well as the relationship between the two parameters for a particular industry are discussed.

Air Pollutants, Occupational↗
PubMed1984

Evaluation of total isocyanate-in-air method using 1-(2-methoxyphenyl)piperazine and HPLC.

The United Kingdom Health and Safety Commission has set a 'common control limit' for workplace exposure to all isocyanates. This limit replaces the previous United Kingdom threshold limit values, which were set for just four species of monomeric isocyanate compounds. This new control limit is set at 20 micrograms of isocyanate group per cubic meter of air expressed as an eight-hour weighted average, and 70 micrograms of isocyanate group per cubic meter of air as a 10-minute weighted average. These new control limits make it necessary that analytical methods should be capable of measuring total isocyanate concentration, including monomers and prepolymers. A previously available method for determining isocyanate monomers using 1-(2-methoxyphenyl)piperazine with high performance liquid chromatography (HPLC) has been modified to measure both monomer and prepolymer. A dual detection system employing electrochemical and ultra-violet detectors is used to identify isocyanate-derived HPLC peaks which are then quantified by reference to a monomer standard, thus avoiding the necessity of isolating prepolymer standards. The total isocyanate-in-air concentration is then calculated from the total area of the isocyanate-derived HPLC peaks. The precision of the method is better than 10% over the range 35 to 140 micrograms(NCO)/m3 for a 10 min sample.

Air Pollutants↗
PubMed1984

A review of world literature finds iron oxides noncarcinogenic.

Iron oxide appeared in the first list of 154 Threshold Limit Values adopted by the American Conference of Governmental Industrial Hygienists at its April 1949 annual meeting. It was set to control dust and fume at the recommended value of 15 mg/M3, at the time, the limit for an inert or "nuisance" dust, and was based on studies of welders made earlier by the U.S. Dept. of Labor and by Drinker and Nelson. By 1964, the TLV was tentatively reduced to 10 mg/M3 after a considerable body of literature had accumulated not only on the health experience of welders, but of other occupations involving iron oxides as well. As a group, these studies indicated that 15 mg/M3 permitted too great accumulations of iron pigmentation in the lung whose chronic retention effects were not known with certainty. Also, an occasional report of cancer of the lungs appeared particularly among British hematite miners, although these findings were immediately questioned on statistical grounds. In seeming confirmation of these early reports of cancer, an alarming number of reports of cancer of the lung and respiratory tract among welders and foundrymen began to appear by 1970, reaching a crescendo by the end of that decade. As past chairman of the TLV Committee, I decided to examine the bases of these findings. This review is the result of this examination.

Animals↗
PubMed1985

Passive colorimetric dosimeter tubes for ammonia, carbon monoxide, carbon dioxide, hydrogen sulfide, nitrogen dioxide and sulfur dioxide.

Colorimetric, stain length, personal dosimeters operating by gas diffusion have been developed to determine worker exposure for up to an eight-hour period for several inorganic airborne contaminants in the range of their Threshold Limit Values. Length of stain, colorimetric dosimeters have been made for the detection of ammonia (NH3), carbon monoxide (CO), carbon dioxide (CO2), hydrogen sulfide (H2S), nitrogen dioxide (NO2), and sulfur dioxide (SO2) in air. For each gas detection system, the sampler depends on the transfer of the gas by diffusion into a glass tube containing a colorimetric length of stain indicator. The stain length developed in a given period of time is compared to a calibration chart to determine, on the spot, the average gas concentration to which the dosimeter has been exposed. These dosimeters are known by the trade name Vapor Gard.

Air Pollutants, Occupational↗
PubMed1985

Ambient levels of selected gases inside swine confinement buildings.

To assess potential worker health hazards, the air in confinement structures on 21 randomly selected swine producing farms in Iowa was evaluated for selected gases. The gases measured (mean concentration) included ammonia (34 ppm), hydrogen sulfide (1.4 ppm), carbon monoxide (9.1 ppm) and carbon dioxide (1640 ppm). Ammonia (compared to other gases) most commonly exceeded the Threshold Limit Value (TLV); however, it was common to find buildings with several gases in excess of the TLV. Buildings housing younger animals were more likely to have hazardous gas levels than buildings housing older animals. This complex mixture of gases represents a potential health hazard to an estimated 400,000 individuals who work in swine confinement buildings. These data suggest that research is needed to control these exposures affecting a large number of workers.

Agriculture↗
PubMed1986

Corporate occupational exposure limits: the current state of affairs.

It has been claimed that the implementation of occupational exposure limits has been instrumental for the near elimination of serious occupational disease in the Western world. Although exposure limits or guides for most large volume chemicals have been established, the majority of the 10,000 chemicals which are routinely used in industry do not have them. As a result, many firms have chosen to establish internal limits to protect their employees as well as the persons who purchase those chemicals. This paper reviews the most important issues discussed in a 2-day symposium on corporate exposure limits which was sponsored by the AIHA Workplace Environment Exposure Limits Committee (WEEL). Thirteen representatives of industry and professional organizations presented papers which addressed various aspects of the process for setting internal exposure limits. The various policies and methodologies used by large American companies which have set limits for many years and their benefits were discussed. The history and function of Threshold Limit Values (TLVs) Maximum Allowable Concentrations (MACs), Permissible Exposure Limits (PELs) and Workplace Environment Exposure Limits (WEELs) also were reviewed. Some of the legal aspects of setting corporate limits and their role in the Product Safety arena were discussed.

Air Pollutants, Occupational↗
PubMed1987

Combined effect of ozone and sulfuric acid on pulmonary function in man.

A potential effect of the combination of ozone and sulfuric acid mist (H2SO4) on respiratory function has been postulated for humans simultaneously exposed to these two pollutants. Nine young men were exposed to 0.25 ppm ozone (O3), 1200-1600 micrograms/m3 sulfuric acid aerosol (H2SO4), and a combination of O3 and H2SO4. During the 2-hr exposures, the subjects exercised (ventilation = 30 L/min) three times for 20 min each. Air temperature was 35 degrees C and relative humidity 83%. Pulmonary function changes after exposure to ozone alone were not expected and were not demonstrated. If a reaction between the combination of O3 and H2SO4 and pulmonary function occurred, pulmonary function responses may have been anticipated following the combination exposure, but no significant changes were seen. It was concluded that the combination of ozone and sulfuric acid aerosol at levels in excess of Threshold Limit Values (TLV) levels do not cause pulmonary dysfunction.

Adolescent↗
PubMed1987

Penetration of methyl isocyanate through organic vapor and acid gas respirator cartridges.

Methyl isocyanate (MIC) is a volatile, toxic chemical [Threshold Limit Value (TLV) = 0.02 ppm] used to manufacture carbamate pesticides. The principal manufacturer of MIC is Union Carbide, and the site of production is Institute, West Virginia. In light of the December 1984 Bhopal, India disaster and possible safety problems at the Institute facility, NIOSH conducted this research as a basis upon which to recommend protective equipment that might be used in an emergency situation where extremely high MIC concentrations might be encountered. Both protective clothing and respirators were evaluated. In particular, NIOSH studied air-purifying respirators in order to assess their effectiveness against MIC vapor penetration. NIOSH does not recommend any air purifying respirator for MIC because of its high toxicity and lack of warning properties and because no effective end of service life indicator currently is available for MIC. This report addresses only MIC penetration through air-purifying cartridges at challenge concentrations designed to simulate emergency escape conditions. Another report addresses the protective clothing issue. The results presented are for two different manufacturers' organic vapor (OV) and acid gas cartridges. Penetration tests were conducted at three or four MIC challenge concentrations and at three different humidity conditions. In general, breakthrough times (1% of challenge concentration) were very short (less than 20 min). Also, high relative humidity was found to decrease the breakthrough time of MIC.

Cyanates↗
PubMed1987

Heat strain and heat stress for workers wearing protective suits at a hazardous waste site.

In order to evaluate the effects of heat stress when full body protective suits are worn, heart rates, oral temperatures and environmental parameters were measured for five unacclimatized male workers (25-33 years of age) who performed sampling activities during hazardous waste clean-up operations. The protective ensembles included laminated PVC-Tyvec chemical resistant hood suits with rubber boots, gloves full facepiece dual cartridge respirators and hard hats. For comparison, measurements also were performed when the men worked at a similar level of activity while they wore ordinary work clothes. A comparison of the heart rates for the men working with and without suits indicated that wearing the suits imposed a heat stress equivalent to adding 6 degrees to 11 degrees C (11 degrees to 20 degrees F) to the ambient WBGT index. A similar result was obtained by calculating the WBGT in the microclimate inside the suits and comparing it to the ambient WBGT. These results indicate the following: 1) there exists a significant risk of heat injury during hazardous waste work when full body protective clothing is worn, and 2) threshold limit values for heat stress established by the ACGIH must be lowered substantially before extending them to cover workers under these conditions.

Adult↗
PubMed1987

Survey of ethylene glycol ether exposures in Belgian industries and workshops.

From 1983 onward, 2654 air samples from 336 different plants from the northern part of Belgium were analyzed for the presence of ethylene glycol ethers. One or more ethylene glycol ethers were detected in 262 air samples (9.9%) covering 78 plants or small establishments (23.2%) from a wide variety of industries. Ethylene glycol ethers were mainly present in establishments or operations where printing pastes, inks, paints and varnishes were used. About one third of the air samples covered various other industries. Car repair shops took a major part of this group. It was not always clear, however, in what precise operation the glycol ethers were involved. The ethylene glycol ethers most frequently identified were ethylene glycol monoethyl ether (EGEE) and its acetate (EGEE-Ac). Furthermore, ethylene glycol monomethyl ether (EGME), its acetate (EGME-Ac), and ethylene glycol monobutyl ether (EGBE) also were present in a large number of air samples. The glycol ethers were not distributed equally among the various groups of operations. Most exposure levels were far below the respective Threshold Limit Value (TLVs) (approximately less than 0.5 x TLV). About 25% of ethylene glycol concentrations, however, were higher than the current TLV. Most of the excursions were slight to moderate, although in selected cases extremely high concentrations were recorded. The majority of air samples revealed complex mixtures of ethylene glycol ethers with other solvents, the glycol ethers often being minor components. The possible implication of these other solvents on glycol ether toxicity and metabolism is discussed.

Air Pollutants, Occupational↗
PubMed1988

Biological monitoring of styrene: a review.

Recent literature about the biological monitoring of styrene-exposed workers is reviewed. Styrene primarily exhibits its toxicity on the central and peripheral nervous systems, although its mutagenicity and chromosome damaging ability also may be relevant. Uptake, transformation and excretion of styrene show that beside the usual biological indicators, such as urinary mandelic and phenylglyoxylic acids (main metabolites), other indicators also may be of interest. These include styrene in expired air, in blood or in urine. Moreover, intermediate or final metabolites such as styrene glycol or mandelic acid in blood also have been proven to be useful in the interpretation of individual values. The most widely used analytical methods for these indicators are gas or high performance liquid chromatography. Correlations between exposure and the different biological indicators mentioned above show that the most reliable indicators are mandelic acid (MA) in urine sampled at the end of the work shift (but not the first day of the week) and the sum of mandelic and phenylglyoxylic acids (MA + PGA) in urine sampled 16 hr after exposure (before the next shift). The biological exposure limit values corresponding to the threshold limit value-time-weighted average (TLV-TWA) of 50 ppm of styrene are 850 mg MA/g creatinine in the end-of-shift sample and 330 mg MA + PGA/g creatinine in the next-morning sample. Other biological indexes, such as styrene glycol (phenyl ethylene glycol) in blood or styrene in urine, look promising but require further research in field situations.

Absorption↗