Effects of Hoods and Flame-Retardant Fabrics on WBGT Clothing Adjustment Factors

Personal protective clothing (PPC) may include hoods and flame-retardant (FR) fabrics that may affect heat transfer and, thus, the critical wet bulb globe temperature (WBGT crit) to maintain thermal equilibrium. The purpose of this study was to compare the differences in WBGT crit for hooded vs. nonhooded versions of particle barrier and vapor barrier coveralls as well as for coveralls made of two flame-retardant fabrics (INDURA cotton and Nomex). Acclimated men (n = 11) and women (n = 4) walked on a treadmill in a climatic chamber at 180 W/m2 wearing four different ensembles: limited-use, particle barrier coveralls with and without a hood (Tyvek 1427), and limited-use vapor barrier coveralls with and without a hood (Tychem QC, polyethylene-coated Tyvek). Twelve of the participants wore one of two flame-retardant coveralls. All participants wore standard cotton clothing. Progressive exposure testing at 50% relative humidity (rh) was designed so that each subject established a physiological steady-state followed by a clear loss of thermal equilibrium. WBGT crit was the WBGT 5 min prior to a loss of thermal equilibrium. Hooded ensembles had a lower WBGT crit than the nonhooded ensembles. The difference suggested a clothing adjustment of 1 degrees C for hoods. There were no significant differences among the FR ensembles and cotton work cloths, and the proposed clothing adjustment for FR coveralls clothing is 0 degrees C.     

Efficiency of five chemical protective clothing materials against nano and submicron aerosols when submitted to mechanical deformations

Due to their potential toxicity, the use of nanoparticles in the workplace is a growing concern. Some studies indicate that nanoparticles can penetrate the skin and lead to adverse health effects. Since chemical protective clothing is the last barrier to protect the skin, this study aims to better understand nanoparticle penetration behaviour in dermal protective clothing under mechanical deformation. For this purpose, five of the most common types of fabrics used in protective clothing, one woven and four nonwoven, were chosen and submitted to different simulated exposure conditions. They were tested against polydispersed NaCl aerosols having an electrical-mobility diameter between 14 and 400 nm. A bench-scale exposure setup and a sampling protocol was developed to measure the level of penetration of the aerosols through the material samples of disposable coveralls and lab coat, while subjecting them to mechanical deformations to simulate the conditions of usage in the workplace. Particle size distribution of the aerosol was determined upstream and downstream using a scanning mobility particle sizer (SMPS). The measured efficiencies demonstrated that the performances of nonwoven materials were similar. Three nonwovens had efficiencies above 99%, while the woven fabric was by far, the least effective. Moreover, the results established that mechanical deformations, as simulated for this study, did not have a significant effect on the fabrics' efficiencies.     

Heat Stress Evaluation of Two-layer Chemical Demilitarization Ensembles with a Full Face Negative Pressure Respirator

The purpose of this study was to examine the heat stress effects of three protective clothing ensembles: (1) protective apron over cloth coveralls including full face negative pressure respirator (APRON); (2) the apron over cloth coveralls with respirator plus protective pants (APRON+PANTS); and (3) protective coveralls over cloth coveralls with respirator (PROTECTIVE COVERALLS). In addition, there was a no-respirator ensemble (PROTECTIVE COVERALLS-noR), and WORK CLOTHES as a reference ensemble. Four acclimatized male participants completed a full set of five trials, and two of the participants repeated the full set. The progressive heat stress protocol was used to find the critical WBGT (WBGT_crit) and apparent total evaporative resistance (R_e,T,a) at the upper limit of thermal equilibrium. The results (WBGT_crit [°C-WBGT] and R_e,T,a [kPa m² W⁻¹]) were WORK CLOTHES (35.5, 0.0115), APRON (31.6, 0.0179), APRON+PANTS (27.7, 0.0244), PROTECTIVE COVERALLS (25.9, 0.0290), and PROTECTIVE COVERALLS-noR (26.2, 0.0296). There were significant differences among the ensembles. Supporting previous studies, there was little evidence to suggest that the respirator contributed to heat stress.     

Prediction of clothing thermal insulation and moisture vapour resistance of the clothed body walking in wind

Clothing thermal insulation and moisture vapour resistance are the two most important parameters in thermal environmental engineering, functional clothing design and end use of clothing ensembles. In this study, clothing thermal insulation and moisture vapour resistance of various types of clothing ensembles were measured using the walking-able sweating manikin, Walter, under various environmental conditions and walking speeds. Based on an extensive experimental investigation and an improved understanding of the effects of body activities and environmental conditions, a simple but effective direct regression model has been established, for predicting the clothing thermal insulation and moisture vapour resistance under wind and walking motion, from those when the manikin was standing in still air. The model has been validated by using experimental data reported in the previous literature. It has shown that the new models have advantages and provide very accurate prediction.     

Heat stress and protective clothing: an emerging approach from the United States.

There is little doubt that heat stress affects many workers adversely and that protective clothing generally adds to the burden. The ACGIH threshold limit value for heat stress is the guiding document for evaluation of heat stress in the United States. Adjustment factors have been used to reflect the change in heat stress imposed by different clothing ensembles. While the first proposed factors started with limited experimental data and professional judgment, heat balance methods in the laboratory have yielded better estimates of adjustment factors and for a wider selection of ensembles. These same experiments have provided the starting point to accounting for nonporous clothing in heat balance evaluation schemes such as required sweat rate. Proposed changes to the ACGIH TLV have been mentioned and a framework for thinking about controls presented.     

Physiological and subjective responses to working in disposable protective coveralls and respirators commonly used by the asbestos abatement industry

The physiological and subjective effects of working with different respirators while wearing lightweight disposable (Tyvek 1412 polyolefin) coveralls commonly used by the asbestos abatement industry were studied. Nine healthy men (mean age = 27.3 yr, weight = 76.9 kg) each performed a series of four exercise tests with four different respirator ensembles in counterbalanced order. Treadmill work was performed at a set walking speed of 4 kph (2.5 mph), 0 percent elevation (220 kcal/hr), a controlled environmental temperature of 33.9 degrees C, and 50% relative humidity. Each test continued up to 120 min, with repeated work/rest intervals of 26 min of work and 4 min of rest. Tyvek disposable coveralls and hoods were worn with each of these four different respirator ensembles: (1) control--a lightweight, low resistance mask; (2) HEPA--an air purifying, full facepiece respirator with dual high efficiency filters; (3) SAR--a supplied-air, pressure-demand respirator with escape filter; (4) SCBA--an open circuit, pressure-demand, self-contained breathing apparatus. Physiological measurements obtained every minute during each test included heart rate and skin and rectal temperatures. Subjective evaluations of clothing, respirator, and facepiece comfort, ease of breathing, temperature and perspiration in the mask and clothing, and respirator load also were measured at the end of the test. Data were analyzed using an analysis of variance. Results indicated that heart rate at the end of the test differed by less than 8 BPM between the control condition and the SCBA (heaviest) condition.(ABSTRACT TRUNCATED AT 250 WORDS)     

WBGT clothing adjustment factors for four clothing ensembles and the effects of metabolic demands

This study measured the clothing adjustment factors (CAFs) for four clothing ensembles (Cotton Coveralls, Tyvek 1427 Coveralls, NexGen Coveralls, and Tychem QC Coveralls; all coveralls were worn without hoods) against a baseline of cotton work clothes to determine whether the CAFs would be affected by the metabolic rate. Fifteen participants wore one of the five ensembles while walking on a treadmill at low, moderate, and high rates of work in an environment maintained at 50% relative humidity. A climatic chamber was used to slowly increase the level of heat stress by increasing air temperature. When the participant's core temperature reached a steady-state, the dry bulb temperature was increased. The point at which the core temperature began to increase was defined as the inflection point, and the WBGT recorded 5 min before the inflection point was the critical WBGT for each ensemble. A three-way mixed effects linear model with ensemble by metabolic rate category interactions demonstrated that the CAF did not change with metabolic rate, so CAFs can be used over a wide range of metabolic rates. The data at the moderate metabolic rate were combined with data on 14 participants from a previous study under the same conditions. The CAFs in degrees C WBGT were 0 for cotton coveralls, 1.0 for Tyvek 1422A, and 2.5 for NexGen. Although the value of 7.5 for Tychem QC was found, the recommendation remained at 10 to account for the effects of humidity. The standard error for the determination of WBGT crit at 50% relative humidity was 1.60 degrees C WBGT.     

Chronic biological effects of methyl methacrylate vapor: III. Histopathology,blood chemistries,and hepatic and ciliary function in the rat

Inhalation experiments were conducted by exposing rats, mice, and frogs to methyl methacrylate (MMA) monomer vapor in air. Rats were exposed for periods of up to 6 months to near threshold limit value (TLV) concentrations and for a shorter period to approximately ten times the TLV. Blood chemistries were unremarkable. Histopathological findings were essentially nil except for microscopic indications of damage to the tracheal mucosa, supported by scanning electron microscopy (SEM) observations that the cilia and microvilli characteristic of these epithelial cells were absent. A reduction in oropharyngeal transport efficiency was shown when frogs were exposed to 400 ppm of MMA vapor. The sodium pentobarbital detoxification function of mouse liver may be altered consequent to exposures to 160 hr to both 100 and 400 ppm of MMA vapor. It is concluded that, at the TLV, cellular responses may be manifested regardless of whether gross systemic effects are seen.     

Heat stress and strain in an aluminum smelter.

Studies of worker heat stress and strain in aluminum smelters have found that heat exposure likely to exceed the American Conference of Governmental Industrial Hygienists' threshold limit value (TLV) and that the dose-response relationship between heat stress and strain was weak. A heat stress model based on climatic data and a task analysis indicated exposures to heat stress in excess of the TLV during the July/August study period. To study the impact of working above the TLV, heat strain data (i.e., oral temperature, recovery heart rate, average heart rate) were collected. Recovery heart rates indicated high strain most of the time, and oral temperatures after peak demands were above the no-strain threshold of 37.5 degrees C about a quarter of the time, indicating that heat stress had an effect. About 95% of the readings were below 38.0 degrees C, the acute oral temperature threshold for a safe exposure. Average heart rates over 6- and 12-hour intervals were generally below acceptable limits of 120 and 110 bpm, respectively. Oral temperature and average heart rates indicated good control of heat stress exposures. Because recovery heart rates were high, some employees were working near their individual limits. The dose-response relationship for recovery heart rate and oral temperature were examined against the level of heat stress above the TLV. There was no relationship between oral temperature and heat stress level. There was an apparent trend toward higher recovery heart rates with heat stress. The lack of a dose-response relationship may be explained by brief periods of very high wet bulb globe temperatures that drove the time-weighted average up out of proportion to the physiological response.     

Maximum sustainable work rate for five protective clothing ensembles with respect to moisture vapor transmission rate and air permeability

The fabrics associated with protective clothing affect heat stress, which influences productivity and risks of heat-related disorders. This study compared the work limiting effects of five protective coveralls and a semiclothed condition (t-shirt and shorts). Two fabric characteristics determined from bench tests, moisture vapor transmission rate (MVTR), and air permeability were also examined as possible predictors of ensemble performance. A progressive metabolic rate protocol was used where environmentalconditions (T(db) = 32 degrees C; T(pwb) = 26 degrees C) were held constant while treadmill speed was slowly increased. The limiting metabolic rate to just maintain thermal equilibrium was the critical point. At this point, critical speed and critical metabolic rate were noted and total evaporative resistance was calculated for each ensemble. Five acclimatized subjects wore each of the six clothing conditions in a random order. Statistically significant differences were found among the five protective garments and a semiclothed ensemble for critical treadmill speed (S(crit)), critical metabolic rate (M(crit)), and total evaporative resistance (R(e-t)). The semiclothed condition (S(crit) = 1.77 m/sec; M(crit) = 580 W; R(e-t) = 0.0099 kPa m2/W) and ensembles made from spunbonded, melt blown, spunbonded polypropylene (SMS) (1.72 m/sec; 560 W; 0.0135 kPa m2/W) and spunbonded polypropylene (1.67 m/sec; 550 W; 0.0126 kPa m2/W) were able to support higher work rates than fabrics made from Tyvek 1422-A (a nonwoven spunbonded olefin) (1.48 m/sec; 470 W; 0.0183 kPa m2/W) and a microporous film supported by spunbonded polypropylene (1.34 m/sec; 420 W; 0.0231 kPa m2/W). A tightly woven polyester ensemble (1.59 m/sec; 510 W; 0.0130 kPa m2/W) had intermediate values and was not significantly different from either group. Air permeability was a better predictor of fabric work limiting performance than MVTR. An air permeability on the order of 10,000 L/min cm2 bar would have little effect on maximum sustainable work.     

A new whole-body vapor exposure chamber for protection performance research on chemical protective ensembles

A chemical vapor exposure chamber was designed to permit the study of whole-body vapor exposure of individuals wearing full protective clothing and equipment systems. A methodology also was developed to quantify the vapor protection performance of chemical protective ensembles (CPE) under safe and validated laboratory procedures. The principal research objectives were to (1) provide a methodology to accurately assess the performance of CPE and equipment under different environmental and chemical vapor challenge conditions; (2) quantify the vapor protection on a per body region basis; (3) have a systems level tool to aid in the research and development of more effective CPE for use in chemical biological environments; and (4) have a safe and reliable means of qualifying new CPE on the basis of vapor protection. Although designed for the evaluation of military-style protective equipment, the procedures apply equally to other styles of CPE used by civilian agencies such as firefighters, police, and hazmat units. The chamber and methodology were specifically designed to examine the vapor protection performance of clothing ensembles, including the details of protection variation over the body. A variety of exposure conditions appropriate to indoor and outdoor scenarios are possible, including the effects of wind, temperature, and relative humidity. Protection performance results from a number of individuals wearing typical military-style CPE are presented. These results demonstrate that there is no such thing as a unique protection performance level obtained for a given CPE. Rather, the individual and the ensemble interact differently in each situation, resulting in a protection performance distribution for individuals, and for groups of wearers, even under a standardized set of exposure conditions.     

Chronic biological effects of methyl methacrylate vapor: II. Body and tissue weights,blood chemistries,and gross metabolic performance in the rat

Chronic exposures of mature male Sprague-Dawley rats to near threshold-limit value (TLV) concentrations of methyl methacrylate (MMA) monomer vapor were conducted in order to assess the effects of such exposures on gross metabolic performance. There was no significant effect on food or water intake or water excretion. Average fecal excretion during the exposure portion of the week tended to be higher in the exposed than in sham-exposed rats. These differences were absent for average values obtained on weekends. Final mean body, adrenal, epididymal fat pad, and popliteal fat pad weights were not significantly different.     

Mortality from non-malignant respiratory disease in the fibreglass manufacturing industry

Objectives: To investigate the question of whether there is an association between workplace exposures and sociodemographic factors and mortality from non-malignant respiratory disease excluding influenza and pneumonia (NMRDxIP) among workers in a fibreglass wool manufacturing facility.

Methods: A case-control study with cases and controls derived from deaths recorded from the Kansas City plant in the Owens Corning mortality surveillance system. The cases are defined as decedents with NMRDxIP as the underlying cause of death. Matched, unadjusted odds ratios (ORs) were used to assess any association between NMRDxIP and cumulative exposure history and sociodemographic factors individually. Matched, adjusted ORs were obtained by conditional logistic regression to estimate the effect of any one variable while controlling for the effect of all the others.

Results: Results of the unadjusted analysis, considering variables one at a time, yielded no significant associations between NMRDxIP and any of the exposure or sociodemographic variables. The smoking OR was substantially increased (OR 5.09; 95%CI 0.65 to undeterimed). Also, there were no significant variables in a conditional logistic regression analysis in which all variables were simultaneously adjusted. ORs for respirable glass fibres were below unity at all concentrations of exposure in the adjusted analysis. For respirable silica there was no consistent relation across all exposure levels. The ORs increased through the first three exposure concentrations but decreased for the highest exposure. However, ORs although not significant, are greater than unity for all respirable concentrations of silica exposure.

Conclusions: The findings for Kansas City show no association between respirable glass fibres and NMRDxIP. The adjusted ORs for all exposures to respirable fibres were less than unity. On the other hand, the ORs for silica exposures were all above unity although there was no clear dose-response relation and none of the ORs were significant. Exposures for all substances considered were very low. Further, given the number of cases and controls, the statistical power to detect relatively small increases in risk, if any increase truly exited, was relatively low. The ORs for exposures to silica were all above unity although there was no clear dose-response relation and none of the ORs were significant. These raised ORs for silica suggest that continued surveillance would be prudent.

     

Occupational Exposure to 1,3-Dichloropropene (Telone® II) in Hawaiian Pineapple Culture

1,3-dichloropropene (DCP), the primary constituent of Telone® II, is a subsoil fumigant that has supplanted 1,2-dibromo-3-chloropropane (DBCP) and ethylene dibromide (EDB) as primary fumigant in Hawaiian pineapple culture. To determine the potential for adverse health effects, an environmental survey was done to assess worker exposures. Exposures were predominantly below 1 ppm, which is the no-effect level determined with experimental animals, and the Threshold Limit Value (TLV) recommended by the American Conference of Governmental Industrial Hygienists (ACGIH).     

Evaluation of Occupational Cold Environments: Field Measurements and Subjective Analysis

The present work is dedicated to the study of occupational cold environments in food distribution industrial units. Field measurements and a subjective assessment based on an individual questionnaire were considered. The survey was carried out in 5 Portuguese companies. The field measurements include 26 workplaces, while a sample of 160 responses was considered for the subjective assessment. In order to characterize the level of cold exposure, the Required Clothing Insulation Index (IREQ) was adopted. The IREQ index highlights that in the majority of the workplaces the clothing ensembles worn are inadequate, namely in the freezing chambers where the protection provided by clothing is always insufficient. The questionnaires results show that the food distribution sector is characterized by a female population (70.6%), by a young work force (60.7% are less than 35 yr old) and by a population with a medium-length professional career (80.1% in this occupation for less than 10 yr). The incidence of health effects which is higher among women, the distribution of protective clothing (50.0% of the workers indicate one garment) and the significant percentage of workers (>75%) that has more difficulties in performing the activity during the winter represent other important results of the present study.     

Evaluation of gowns and coveralls used by medical personnel working with Ebola patients against simulated bodily fluids using an Elbow Lean Test

Gowns and coveralls are important components of protective ensembles used during the management of known or suspected Ebola patients. In this study, an Elbow Lean Test was used to obtain a visual semi-quantitative measure of the resistance of medical protective garments to the penetration of two bodily fluid simulants. Tests were done on swatches of continuous and discontinuous regions of fabrics cut from five gowns and four coveralls at multiple elbow pressure levels (2–44 PSI). Swatches cut from the continuous regions of one gown and two coveralls did not have any strike-through. For discontinuous regions, only the same gown consistently resisted fluid strike-through. As hypothesized, with the exception of one garment, fluid strike-through increased with higher applied elbow pressure, was higher for lower fluid surface tension, and was higher for the discontinuous regions of the protective garments.     

Worker exposure and protective clothing performance during manual seed treatment with lindane

Twelve workers were monitored for exposure to 18.75% lindane dust formulation during manual wheat seed treatment. The mean total actual exposure rate was 32.89 mg/hr. Potential respiratory exposure averaged 0.0057 mg/hr (<1% of the total), with seven workers receiving no measurable respiratory exposures. Mean hand exposure was 1.84 mg/hr (5.6%). Dermal exposure to the head and neck averaged 4.28 mg/hr (13%). Exposure measured beneath the workshirt and workpants averaged 26.8 mg/hr (81.4%). The workshirt and workpants provided 3.4-fold and 11.5-fold protection factors, respectively. Forearm exposure measured beneath the workshirt represented more than 40% of total actual exposure. The small contribution of hand exposure to total dermal exposure was consistent with the use of chemical-resistant gloves by all workers. Total dermal exposure could be reduced substantially by wearing coveralls over regular work clothing, and by the use of gauntlet-type gloves. It is recommended that worker education concerning personal hygiene and the appropriate use of protection clothing be made essential components of exposure reduction programs.     

Exposure of farmers to phosmet, a swine insecticide

OBJECTIVES: The goal of this study was to measure dermal and inhalation exposures to phosmet during application to animals and to identify what determinants of exposure influence the exposure levels. METHODS: Ten farmers were monitored using dermal patches, gloves, and air sampling media during normal activities of applying phosmet to pigs for insect control. Exposures were measured on the clothing (outer), under the clothing (inner), on the hands, and in the air. Possible exposure determinants were identified, and a questionnaire on work practices was administered. RESULTS: The geometric mean of the outer exposure measurements was 79 microg/h, whereas the geometric mean of the inner exposure measurements was 6 microg/h. The geometric mean for hand exposure was 534 microg/h, and the mean air concentration was 0.2 microg/m3. Glove use was associated with the hand and total dermal exposure levels, but no other determinant was associated with any of the exposure measures. The average penetration through the clothing was 54%, which dropped to 8% when the farmers wearing short sleeves were excluded. The farmers reported an average of 40 hours a year performing insecticide-related tasks. CONCLUSIONS: Farmers who applied phosmet to animals had measurable exposures, but the levels were lower than what has been seen in other pesticide applications. Inhalation exposures were insignificant when compared with dermal exposures, which came primarily from the hands. Clothing, particularly gloves, provided substantial protection from exposures. No other exposure determinant was identified.