Short-term Exposure Limit Research Articles

Use of Methanol as a Coolant During Machining of Aluminum in a Shipbuilding Environment: A Failure to Assess and Manage Risk

Minimization of harm during the conduct of work is one of the most important tenets of industrial hygiene. Organizations make changes to solve perceived problems. What appears to be expedient for solving a problem can create serious risks totally unrecognized by the proponent. This investigation reports on such a situation involving the use of methanol as a lubricant during machining of aluminium panels using a router. Spot samples for methanol were measured using colorimetric detector tubes and samples of long duration by colorimetric diffusion tubes utilizing similar chemistry. Both were positioned in the breathing zone. Most of the spot samples exceeded the 8-hour TLV-TWA (Threshold Limit Value-Time-Weighted Average) of 200 ppm and the TLV-STEL (Short-Term Exposure Limit) of 250 ppm. The two long duration samples also exceeded the TLV-TWA. A change in the operation prevented collection of additional long duration samples. By these measures, workers were overexposed to methanol during this activity. An additional serious consequence from use of methanol in this manner was risk of fire. This situation illustrates the complexity of decisions affecting workplace operations. What appears to be expedient for solving a problem may be totally inappropriate.

Quantification of volatile organic compounds in smoke from prescribed burning and comparison with occupational exposure limits

Abstract. Prescribed burning represents a serious threat to personnel fighting fires due to smoke inhalation. The aim of this study was to investigate exposure by foresters to smoke from prescribed burning, focusing on exposure to volatile organic compounds (VOCs). The methodology for smoke sampling was first evaluated. Potentially dangerous compounds were identified among the VOCs emitted by smoke fires at four prescribed burning plots located around Corsica. The measured mass concentrations for several toxic VOCs were generally higher than those measured in previous studies due to the experimental framework (short sampling distance between the foresters and the flame, low combustion, wet vegetation). In particular, benzene, phenol and furfural exceeded the legal short-term exposure limits published in Europe and/or the United States. Other VOCs such as toluene, ethybenzene or styrene remained below the exposure limits. In conclusion, clear and necessary recommendations were made for protection of personnel involved in fighting fires.

Acute effects of inhaled sulphur dioxide on pig nasal vascular and airway resistances.

People complain about nasal stuffiness after SO2 exposure. This study was to investigate the acute effects of SO2 on nasal vascular and airway resistances in anaesthetized pigs for elucidating the underlying vascular and control mechanisms. Controlled ventilation was passed to the lungs or retrogradely through each nasal cavity. Nasal airway and lower airway pressures were measured to reflect airflow resistance changes. Systemic arterial pressure and nasal arterial flow were measured to calculate nasal vascular resistance. Nasal and pulmonary SO2 challenges were given. At 2 ppm, SO2 decreased systemic blood pressure and nasal vascular resistance but increased nasal airway and lower airway resistances. With increasing level to 8 ppm, SO2 increased systemic arterial pressure, nasal vascular and lower airway resistances but decreased nasal airway resistance. Nasal and pulmonary challenges induced similar responses. Ipsilateral nasal challenge elicited bilateral responses. Ruthenium red abolished the responses to nasal challenges. Bilateral vagosympathectomy eliminated the responses to lung challenges. Hence, SO2 at 2 ppm causes nasal congestion through sensory reflex vasodilatation but at higher levels nasal decongestion through sensory reflex vasoconstriction. Nasal congestion coupled with bronchoconstriction at levels of SO2 below short-term exposure limit (STEL) (≤ 2 ppm) would limit SO2 entering the lungs. Nasal decongestion at levels of SO2 beyond STEL (> 2 ppm) can effectively decrease total airway resistance as concurrent strong bronchoconstriction may impair ventilation.

Methyl Methacrylate Levels in Orthopedic Surgery: Comparison of Two Conventional Vacuum Mixing Systems

Poly-methyl methacrylate bone cements contain methyl methacrylate (MMA), which is known for its sensitizing and toxic properties. Therefore, in most European countries and in the USA, guidelines or regulations exist for occupational exposures. The use of vacuum mixing systems can significantly reduce airborne MMA concentrations during bone setting. Our goal was to test two commonly used vacuum mixing systems (Palamix(®) and Optivac(®)) using Palacos(®) R bone cement for their effectiveness at preventing MMA vapor release in a series of standardized trials in a laboratory as well as in an operating theatre. MMA was quantified every second over a period of 3 min using a photoionization detector (MiniRAE(®) 3000) device positioned in the breathing area of the user. Significant differences in MMA mean vapor concentrations over 180 s were observed in the two experimental spaces, with the highest mean concentrations (7.61 and 7.98 ppm for Palamix(®) and Optivac(®), respectively) observed in a laboratory with nine air changes per hour and the lowest average concentrations (1.06 and 1.12 ppm for Palamix(®) and Optivac(®), respectively) in an operating theatre with laminar flow ventilation and 22 air changes per hour. No significant differences in overall MMA concentrations were found between the two vacuum mixing systems in either location. Though, differences were found between both systems during single mixing phases. Thus, typical handling of MMA in orthopedic procedures must be seen as not harmful as concentrations do not reach the short-term exposure limit of 100 ppm. Additionally, laminar airflow seems to have an influence on lowering MMA concentrations in operation theatres.

Prevalence of formaldehyde in indoor air of gross anatomy laboratory and cadaver storage room of a medical college

Aim: Concentration of formaldehyde (FA) which is used to preserve cadavers for dissection in medical colleges was monitored in indoor air including at the breathing level in dissection classes during a 2-week study in a gross anatomy laboratory and also in the cadaver storage room in a Medical College in India in 2012. Materials and Methods: Air samples were collected for 30 min and 3 h to commensurate with World Health Organization (WHO) standard (short-term exposure limit) value of FA (30-min) and dissection class of 3 h duration respectively. Results: FA concentration ranged from 0.11 to 1.07 mg/m3 in the cadaver storage room and 0.06-1.12 mg/m3 in the gross anatomy laboratory. In samples taken at 5 ft height at the breathing level, FA concentration ranged from 0.32 to 0.86 mg/m3. Conclusions: Most of the observed FA levels were found to be above the prescribed FA guideline values laid down by organizations such as OSHA, ACGIH, WHO, Japan Ministry of Health, Labor, and Welfare and, therefore, could be considered as harmful for students’ and teachers’ health. FA concentrations reported from a few medical facilities in other countries are comparable, implying that some uniform management and control strategies for FA could be contemplated to reduce risks of FA exposure to students and teachers which are discussed in this paper.

Hydrogen Sulfide Gas Emissions during Disturbance and Removal of Stored Spent Mushroom Compost

Spent mushroom compost (SMC) is a by-product of the mushroom industry that is used as an agricultural fertilizer. In Europe, SMC storage and use are governed by EU Nitrates Directive 91/676/EEC to protect waterways against pollution by nitrates. A health and safety risk was identified during the removal of stored SMC for land application, as the stored SMC released high levels of toxic H2S gas into the atmosphere when disturbed. In this study, emissions of H2S were monitored at two outdoor and two indoor locations where stored SMC was being removed for land application. A repeating peak-trough pattern of H2S emissions was detected at all sites, with peaks corresponding to periods of active disturbance of SMC. The highest H2S concentrations (10 s average) detected at the SMC face were, respectively, 680 and 2083 ppm at outdoor sites 1 and 2, and 687 and 89 ppm at indoor sites 3 and 4. Higher concentrations of H2S were released from older SMC compared to newer material. Indoor-stored SMC had lower moisture content (53% to 65%) compared to outdoor-stored material (66% to 72%), while the temperature of indoor-stored SMC was higher (33 degrees C to 51 degrees C) compared to outdoor-stored material (24 degrees C to 36 degreees C). The current short-term exposure limit (STEL) of 10 ppm was exceeded at all sites except site 4, which was smaller than the other sites, indicating a significant health and safety risk associated with working in the vicinity of stored SMC when it is being actively disturbed. Results suggest that SMC stored under cover in small heaps (600 m3) emits less H2S during disturbance and removal compared to SMC stored outdoors in large heaps (> 1500 m3). This should be taken into consideration in the design, construction, and management of SMC storage facilities. Health and safety protocols should be in place at SMC storage facilities to cover the risks of exposure to toxic H2S gas during disturbance of stored SMC.

Short Duration Needle Trap Sampling with Gas Chromatography Analysis to Determine Nearly Instantaneous Concentrations of Selected Organic Vapor Contaminants

Needle trap device samplers were used for rapid (60 s) quantitative sampling of short-term exposure limit (STEL) and peak exposure standard concentrations using a manually operated pump to collect small volume (10 mL) gas phase samples containing methylene chloride, benzene, toluene, and tetrachloroethylene vapors. Solventless introduction of chemical samples for gas chromatography analysis with flame ionization detection yielded linear results (R2 > 0.99) for vapor standard mixtures of the four target analytes ranging from 10% to 200% of their respective nominal STEL or peak exposure standard concentrations. Needle trap samplers showed ≥86% recovery (as GC-FID peak area responses) following 14-day storage at room temperature compared to the same samplers analyzed immediately, with better recovery values observed with shorter storage (≥95% at room temperature for seven days, except for methylene chloride) or with storage at 4°C. Calibration for quantitation of concentrations of benzene, toluene, and tetrachloroethylene was shown to be possible with the use of an internal standard to account for injector discrimination between the solventless NTD approach and injections of target analytes in carbon disulfide. Due to the simple sampling method (no field calibration and battery-free pumping) and the avoidance of solvent dilution, a needle trap sampling approach could simplify sample collection and analysis to chromatographically determine nearly instantaneous (1 min) exposure concentrations.

Gas Emissions and Metallic Contents of Commonly Used Fuelwood in Nigeria

Gas emissions levels of NO, NO2, SO2, CO, and CO2 from commonly used domestic fuel wood were investigated using Carbolite Muffler Furnace equipped with gas probes. Results after analysis showed gas levels in ppm in the range 0.1–29.6 for NO, 0.1–10.0 for NO2, 1.2–21.0 for SO2, 0–0.2 for CO, and 90–560 for CO2. Analysis of the resulting wood ash showed metal levels in gkg-1 in the range 2.16–10.37 for Ca, 0.29–1.58 for Mg, 1.04–3.53 for Zn, and 0.24–0.84 for Al. Compared to the recommended short term exposure limits, the observed gas levels of SO2 and NO2 indicate environmentally unfriendly nature of some of the commonly used domestic fuel wood and the possible risk of respiratory, pulmonary and carcinogenic diseases that could be associated with their regular usage. The wood ash composition suggests it could serve a friendly utilization as soil additive for agricultural purposes for soils whose compositions show deficiency of these metals.

Gas Dielectric Transistor of CuPc Single Crystalline Nanowire for SO2 Detection Down to Sub‐ppm Levels at Room Temperature

Sulfur dioxide (SO 2 ) is one of the most dangerous air pollutants that impair environment and human health. SO 2 in air is released during the burning of fossil fuels and plays one major role in the formation of acid rain. The repeated exposure to low levels of SO 2 can cause permanent pulmonary impairment for humans. [ 1 ] The long and short-term exposure limits for SO 2 gas are 2 and 5 ppm, respectively, [ 1 , 2 ] and the U. S. Environmental Control Agency has set the acceptable limit for SO 2 in ambient air at a level of 0.5 ppm. [ 3 ] It is of great importance to measure low concentration of SO 2 in air accurately and fast for human health protection and air-quality monitoring. Semiconductor resistor sensors are, for more than 30 years, one of the most common used gas sensors to detect toxic and fl ammable gases such as NO 2 , H 2 S, CO, NH 3 , and H 2 because of their distinguished merits such as low cost, long lasting, high sensitivity, and good reliability, etc. [ 4 ] Organic fi eld-effect transistor (OFET) is another alternative semiconductor sensing technology with advantages over resistors, and has attracted much attention only recently. [ 5 ] The sensitivity can be dramatically enhanced by changing the source-drain current ( I SD ) of OFET when operating the sensors in the sub-threshold regime, as a result of the current modulation by the extra gate electrode. [ 6 ] Another advantage of OFET sensors is that the sensing response can be enhanced by integrating them in oscillator and adaptive amplifi er circuits. [ 7 ] These advantages combined with low cost and light weight of organic semiconductors ensure that OFET sensors have attracted much attention for the detection of a wide range of gases. [ 8 ]

Mobile Decontamination Units—Room for Improvement?

Mobile decontamination units are intended to be used at the accident site to decontaminate persons contaminated by toxic substances. A test program was carried out to evaluate the efficacy of mobile decontamination units. The tests included functionality, methodology, inside environment, effects of wind direction, and decontamination efficacy. Three different types of units were tested during summer and winter conditions. Up to 15 test-persons per trial were contaminated with the imitation substances Purasolve ethyl lactate (PEL) and methyl salicylate (MES). Decontamination was carried out according to standardized procedures. During the decontamination trials, the concentrations of the substances inside the units were measured. After decontamination, substances evaporating from test-persons and blankets as well as remaining amounts in the units were measured. The air concentrations of PEL and MES inside the units during decontamination in some cases exceeded short-term exposure limits for most toxic industrial chemicals. This was a problem, especially during harmful wind conditions, i.e., wind blowing in the same direction as persons moving through the decontamination units. Although decontamination removed a greater part of the substances from the skin, the concentrations evaporating from some test-persons occasionally were high and potentially harmful if the substances had been toxic. The study also showed that blankets placed in the units absorbed chemicals and that the units still were contaminated five hours after the end of operations. After decontamination, the imitation substances still were present and evaporating from the contaminated persons, blankets, and units. These results indicate a need for improvements in technical solutions, procedures, and training.

Modelling Occupational Inhalation Exposure to Concentration Peaks of Chemicals and Associated Health Risk Assessment

The aims of this study were to estimate inhalation exposure to chemicals and the resulting acute health risks for working scenarios characterized by successive peaks of pollutant concentrations. A stochastic two-zone model combining a time-varying emission function and field-derived probabilistic distributed input parameter was used to predict both instantaneous and 15-min averaged pollutant concentrations during the decanting operations performed in a pathology laboratory. The location of the workers was taken into account in the model for computing probability distributions of inhalation exposures and for subsequently characterizing hazard quotients (HQ) for health risk purposes. The model was assessed by comparison with repeated individual monitoring performed on the workers during the same tasks. Modelled inhalation exposure profiles revealed 15-min average concentrations of 1.7 and 208 mg m(-) (3) for formaldehyde (FA) and toluene (TOL), respectively. The individual monitoring performed showed similar average concentrations, with 1.2 and 175 mg m(-) (3) for FA and TOL. No more than three to five successive FA concentration peaks were generally sufficient in the modelling exercise to provide 15-min estimated exposures exceeding short-term exposure limits (STEL). Modelled HQ higher than unity and STEL exceedance probabilities higher than 0.5 were found for FA, whereas estimated TOL health risks were notably lower according to high exposure limits. Estimated inhalation exposure distributions frequently ranged over one order of magnitude for the two pollutants, reflecting both the natural exposure variability and the uncertainty of some of the two-zone model input parameters. These findings indicate that the developed approach may be useful for modelling occupational exposures and acute health risks related to chemicals in situations involving time-varying emission sources. Modelled exposure distributions may also be used within Bayesian decision analysis frameworks for making exposure judgements and refining risk management measures.

Airborne Isocyanate Exposures in the Collision Repair Industry and a Comparison to Occupational Exposure Limits

Isocyanate exposure was evaluated in 33 spray painters from 25 Washington State autobody shops. Personal breathing zone samples (n = 228) were analyzed for isophorone diisocyanate (IPDI) monomer, 1,6-hexamethylene diisocyanate (HDI) monomer, IPDI polyisocyanate, and three polyisocyanate forms of HDI. The objective was to describe exposures to isocyanates while spray painting, compare them with short-term exposure limits (STELs), and describe the isocyanate composition in the samples. The composition of polyisocyanates (IPDI and HDI) in the samples varied greatly, with maximum amounts ranging from up to 58% for HDI biuret to 96% for HDI isocyanurate. There was a significant inverse relationship between the percentage composition of HDI isocyanurate to IPDI and to HDI uretdione. Two 15-min STELs were compared: (1) Oregon's Occupational Safety and Health Administration (OR-OSHA) STEL of 1000 μg/m3 for HDI polyisocyanate, and (2) the United Kingdom's Health and Safety Executive (UK-HSE) STEL of 70 μg NCO/m3 for all isocyanates. Eighty percent of samples containing HDI polyisocyanate exceeded the OR-OSHA STEL while 98% of samples exceeded the UK-HSE STEL. The majority of painters (67%) wore half-face air-purifying respirators while spray painting. Using the OR-OSHA and the UK-HSE STELs as benchmarks, 21% and 67% of painters, respectively, had at least one exposure that exceeded the respirator's OSHA-assigned protection factor. A critical review of the STELs revealed the following limitations: (1) the OR-OSHA STEL does not include all polyisocyanates, and (2) the UK-HSE STEL is derived from monomeric isocyanates, whereas the species present in typical spray coatings are polyisocyanates. In conclusion, the variable mixtures of isocyanates used by autobody painters suggest that an occupational exposure limit is required that includes all polyisocyanates. Despite the limitations of the STELs, we determined that a respirator with an assigned protection factor of 25 or greater is required to protect against isocyanate exposures during spray painting. Consequently, half-face air-purifying respirators, which are most commonly used and have an assigned protection factor of 10, do not afford adequate respiratory protection.

Assessing Formaldehyde Exposure in Your Gross Lab: Occupational Exposure Limits and Best Practices

Anatomists’ formaldehyde exposures often exceed Occupational Exposure Limits (OELs) set to minimize risks of cancer, allergy and irritation. OELs vary worldwide. The U.S. OSHA regulatory 8‐hour OEL is 0.75 ppm with an Action Level of 0.5 ppm. The 15‐minute Short Term Exposure Limit is 2 ppm. The American Conference of Governmental Industrial Hygienists (ACGIH) recommends a lower Ceiling Limit of 0.3 ppm, which is in use by many countries and is designed to prevent eye and upper respiratory tract irritation. Personal breathing zone air samples are preferred and are typically >2 times higher than area samples. Short‐term sampling captures worst case exposures such as initial dissection of the cranium, abdomen and thoracic cavity. Passive, active and real‐time techniques each have benefit and will be discussed along with the value of using credentialed industrial/occupational hygienists, validated sampling methods and accredited laboratories where available. In the U.S., formaldehyde levels at or above the OSHA Action Level of 0.5 ppm trigger required signage, training, medical monitoring, and personal protective equipment. The challenges of formaldehyde respirator use in gross anatomy labs will be reviewed via a case study. Risk management of sensitive individuals due to pregnancy, asthma or formaldehyde allergy and unregulated individuals such as students and volunteers will also be addressed.

The Occupational Exposure Limit for Fluid Aerosol Generated in Metalworking Operations: Limitations and Recommendations

The aim of this review was to assess current knowledge related to the occupational exposure limit (OEL) for fluid aerosols including either mineral or chemical oil that are generated in metalworking operations, and to discuss whether their OEL can be appropriately used to prevent several health risks that may vary among metalworking fluid (MWF) types. The OEL (time-weighted average; 5 mg/m3, short-term exposure limit ; 15 mg/m3) has been applied to MWF aerosols without consideration of different fluid aerosol-size fractions. The OEL, is also based on the assumption that there are no significant differences in risk among fluid types, which may be contentious. Particularly, the health risks from exposure to water-soluble fluids may not have been sufficiently considered. Although adoption of The National Institute for Occupational Safety and Health's recommended exposure limit for MWF aerosol (0.5 mg/m3) would be an effective step towards minimizing and evaluating the upper respiratory irritation that may be caused by neat or diluted MWF, this would fail to address the hazards (e.g., asthma and hypersensitivity pneumonitis) caused by microbial contaminants generated only by the use of water-soluble fluids. The absence of an OEL for the water-soluble fluids used in approximately 80-90 % of all applicants may result in limitations of the protection from health risks caused by exposure to those fluids.

Efficacy, efficiency and safety aspects of hydrogen peroxide vapour and aerosolized hydrogen peroxide room disinfection systems

This was a head-to-head comparison of two hydrogen-peroxide-based room decontamination systems. To compare the efficacy, efficiency and safety of hydrogen peroxide vapour (HPV; Clarus R, Bioquell, Andover, U.K.) and aerosolized hydrogen peroxide (aHP; SR2, Sterinis, now supplied as Glosair, Advanced Sterilization Products (ASP), Johnson & Johnson Medical Ltd, Wokingham, U.K.) room disinfection systems. Efficacy was tested using 4- and 6-log Geobacillus stearothermophilus biological indicators (BIs) and in-house prepared test discs containing approximately 10(6) meticillin-resistant Staphylococcus aureus (MRSA), Clostridium difficile and Acinetobacter baumannii. Safety was assessed by detecting leakage of hydrogen peroxide using a hand-held detector. Efficiency was assessed by measuring the level of hydrogen peroxide using a hand-held sensor at three locations inside the room, 2 h after the start of the cycles. HPV generally achieved a 6-log reduction, whereas aHP generally achieved less than a 4-log reduction on the BIs and in-house prepared test discs. Uneven distribution was evident for the aHP system but not the HPV system. Hydrogen peroxide leakage during aHP cycles with the door unsealed, as per the manufacturer's operating manual, exceeded the short-term exposure limit (2 ppm) for more than 2 h. When the door was sealed with tape, as per the HPV system, hydrogen peroxide leakage was <1 ppm for both systems. The mean concentration of hydrogen peroxide in the room 2 h after the cycle started was 1.3 [standard deviation (SD) 0.4] ppm and 2.8 (SD 0.8) ppm for the four HPV and aHP cycles, respectively. None of the readings were <2 ppm for the aHP cycles. The HPV system was safer, faster and more effective for biological inactivation.

Penetration patterns of monomeric and polymeric 1,6-hexamethylene diisocyanate monomer in human skin

We investigated penetration patterns of monomeric and polymeric 1,6-hexamethylene diisocyanate (HDI), experimentally and as part of commercial products, in excised full-thickness human skin at 5, 10, 30, or 60 min after exposure. We observed that both monomeric and polymeric HDI were readily absorbed into the skin and that the clearcoat composition affects the penetration rate of the individual isocyanates. The short-term absorption rates for HDI monomer, biuret, and isocyanurate were determined and used to estimate the exposure time required to reach a body burden equal to the American Conference of Governmental Industrial Hygienists (ACGIH) inhalation threshold limit value (TLV) or Oregon State occupational exposure limit (OEL). Oregon is the only government entity in the United States to promulgate a short-term exposure limit (STEL) for HDI-based polyisocyanates biuret and isocyanurate. Based on these absorption rates for a slow-drying clearcoat after 10 min (1.33 μg cm(-2) h(-1)) or 60 min (0.219 μg cm(-2) h(-1)), we calculated that 6.5 and 40 min dermal exposure, respectively, is required to achieve a dose of HDI equivalent to the ACGIH TLV. For biuret, the time to achieve a dose equivalent to the Oregon OEL for slow-drying clearcoat was much shorter (<31 min) than that for fast-drying clearcoat (618 min). Isocyanurate had the shortest skin absorption times regardless of clearcoat formulation (14 s-1.7 min). These results indicate that the dose received through dermal exposure to HDI-containing clearcoats has a significant potential to exceed the dose equivalent to that received through inhalation exposure at established regulatory limits. A critical need exists to monitor dermal exposure quantitatively in exposed workers, to use proper protective equipment to reduce dermal exposure, and to re-evaluate regulatory exposure limits for isocyanates.

Use of the Reciprocal Calculation Procedure for Setting Workplace Emergency Action Levels for Hydrocarbon Mixtures and their Relationship to Lower Explosive Limits

This paper proposes a novel use of the reciprocal calculation procedure (RCP) to calculate workplace emergency action levels (WEALs) for accidental releases of hydrocarbon mixtures. WEALs are defined here as the concentration in air that area monitors should alarm at to provide adequate warning and be sufficiently protective of health to allow at least enough time to don respiratory protective equipment (RPE) and escape. The rationale for the approach is analysed, and ways of defining suitable substance group guidance values (GVs) for input into the RCP are considered and compared. WEAL GVs could be based on: 3× RCP GVs (i.e. using the 3× rule), the 5× RCP GVs (i.e. using the 5× rule for calculating ceiling values), emergency exposure limits, or immediately dangerous to life or health values (IDLHs). Of these, the method of choice is to base WEAL GVs on health-based IDLH values, which were developed for emergency situations in the workplace. However, IDLHs have only been set for 11 hydrocarbons, so the choice of GVs is also informed by comparison with possible GVs based on the other approaches. Using the proposed GVs, WEALs were calculated for various hydrocarbon mixtures, and the way they vary with the composition of the mixture was examined. Also, the level of health protection given by the current practice of setting emergency area alarms in the oil and gas industry at 10% of the lower explosive limit (LEL) was tested by comparing this with the WEAL. In the event of an accidental release, this comparison suggests that, provided that aromatics constitute <50% of the mixture, an alarm set at 10% LEL should provide adequate warning and be sufficiently protective of health to at allow at least enough time to don RPE and escape. In the absence of better information or specific acute toxicity concerns (such as the presence of hydrogen sulphide), it is proposed that the WEALs be used as a guide for assessing the adequacy of area alarm levels in respect of warning of an acute health risk. This work is exploratory (e.g. other rationales for setting GVs are possible) and the approach needs testing on further real-life samples. Although not explored here, the RCP approach may also lend itself to the calculation of in-house short-term exposure limits for hydrocarbon mixtures and other mixtures where the acute toxic end points of the components are similar.

A weight of evidence approach for the assessment of the ototoxic potential of industrial chemicals

There is accumulating epidemiological evidence that exposure to some solvents, metals, asphyxiants and other substances in humans is associated with an increased risk of acquiring hearing loss. Furthermore, simultaneous and successive exposure to certain chemicals along with noise can increase the susceptibility to noise-induced hearing loss. There are no regulations that require hearing monitoring of workers who are employed at locations in which occupational exposure to potentially ototoxic chemicals occurs in the absence of noise exposure. This project was undertaken to develop a toxicological database allowing the identification of possible ototoxic substances present in the work environment alone or in combination with noise exposure. Critical toxicological data were compiled for chemical substances included in the Quebec occupational health regulation. The data were evaluated only for noise exposure levels that can be encountered in the workplace and for realistic exposure concentrations up to the short-term exposure limit or ceiling value (CV) or 5 times the 8-h time-weighted average occupational exposure limit (TWA OEL) for human data and up to 100 times the 8-h TWA OEL or CV for animal studies. In total, 224 studies (in 150 articles of which 44 evaluated the combined exposure to noise and a chemical) covering 29 substances were evaluated using a weight of evidence approach. For the majority of cases where potential ototoxicity was previously proposed, there is a paucity of toxicological data in the primary literature. Human and animal studies indicate that lead, styrene, toluene and trichloroethylene are ototoxic and ethyl benzene, n-hexane and p-xylene are possibly ototoxic at concentrations that are relevant to the occupational setting. Carbon monoxide appears to exacerbate noise-induced hearing dysfunction. Toluene interacts with noise to induce more severe hearing losses than the noise alone.

Estimates of Radiation Exposures for Human Crews in Deep Space from the January 15, 2005, Solar Energetic Particle Event Using the Earth-Moon-Mars Radiation Environment Module

The Earth-Moon-Mars Radiation Environment Module (EMMREM) is a numerical model for characterizing the time-dependent radiation environment in the Earth-Moon-Mars and interplanetary space environments. In this work we demonstrate the capabilities of the module for performing analyses of time-dependent exposures from solar energetic particle (SEP) events near Earth and Mars by calculating time-dependent dose rates, dose equivalent rates, and accumulated dose and accumulated dose equivalents for surrogates of the skin and the blood forming organs (BFOs) of crew members shielded by as much as 10 g/cm2 of aluminum shielding for the January 15, 2005, SEP event. The motivation for the development of EMMREM is the need to better understand the radiation hazards in deep space and near Earth and other planetary bodies, in near real time in support of possible future space exploration by manned and unmanned spacecraft. Characterizing the radiation environment for different locations on and close to Earth for SEP events is fairly well developed. However, estimating the probable radiation environment near Mars and other locations throughout the solar system is not currently supported for SEP events. Such capability is critical for future human exploration of the Moon and Mars in the upcoming decades. The calculated doses for the skin and BFO surrogates are compared with the National Aeronautics and Space Administration’s short-term permissible exposure limits.

Quantification of VX Vapor in Ambient Air by Liquid Chromatography Isotope Dilution Tandem Mass Spectrometric Analysis of Glass Bead Filled Sampling Tubes

An analysis method has been developed for determining low parts-per-quadrillion by volume (ppqv) concentrations of nerve agent VX vapor actively sampled from ambient air. The method utilizes glass bead filled depot area air monitoring system (DAAMS) sampling tubes with isopropyl alcohol extraction and isotope dilution using liquid chromatography coupled with a triple-quadrupole mass spectrometer (LC/MS/MS) with positive ion electrospray ionization for quantitation. The dynamic range was from one-tenth of the worker population limit (WPL) to the short-term exposure limit (STEL) for a 24 L air sample taken over a 1 h period. The precision and accuracy of the method were evaluated using liquid-spiked tubes, and the collection characteristics of the DAAMS tubes were assessed by collecting trace level vapor generated in a 1000 L continuous flow chamber. The method described here has significant improvements over currently employed thermal desorption techniques that utilize a silver fluoride pad during sampling to convert VX to a higher volatility G-analogue for gas chromatographic analysis. The benefits of this method are the ability to directly analyze VX with improved selectivity and sensitivity, the injection of a fraction of the extract, quantitation using an isotopically labeled internal standard, and a short instrument cycle time.