An update on the detoxification processes for silica particles and asbestos fibers: successess and limitations

Inhalation of asbestos fibers and crystalline silica produces a number of diseases including fibrosis and cancer. Investigations into the mechanisms involved in mineral particle-induced toxicity indicated the importance of their surfaces in the pathological consequences. Masking of the surface sites has therefore featured prominently in a number of detoxification processes that have been investigated. The majority of the detoxification processes were, however, conducted to elucidate the involvement of a particular surface site in the toxicity of a specific mineral. Others were investigated with the aim of large industrial applications to be applied during mining, handling, processing, transporting, and disposing of minerals. It can be concluded that, to date, there is no single detoxification process that could be applied universally to all different types of mineral particles. Those that have shown some success could not completely abolish all adverse effects. Further elucidation of mechanisms of particle-induced toxicity may open new possibilities for detoxification processes.

Respiratory protection provided by N95 filtering facepiece respirators against airborne dust and microorganisms in agricultural farms

A new system was used to determine the workplace protection factors (WPF) for dust and bioaerosols in agricultural environments. The field study was performed with a subject wearing an N95 filtering facepiece respirator while performing animal feeding, grain harvesting and unloading, and routine investigation of facilities. As expected, the geometric means (GM) of the WPFs increased with increasing particle size ranging from 21 for 0.7-1 microm particles to 270 for 5-10 microm particles (p < 0.001). The WPF for total culturable fungi (GM = 35) was significantly greater than for total culturable bacteria (GM = 9) (p = 0.01). Among the different microorganism groups, the WPFs of Cladosporium, culturable fungi, and total fungi were significantly correlated with the WPFs of particles of the same sizes. As compared with the WPFs for dust particles, the WPFs for bioaerosols were found more frequently below 10, which is a recommended assigned protection factor (APF) for N95 filtering facepiece respirators. More than 50% of the WPFs for microorganisms (mean aerodynamic diameter < 5 microm) were less than the proposed APF of 10. Even lower WPFs were calculated after correcting for dead space and lung deposition. Thus, the APF of 10 for N95 filtering facepiece respirators seems inadequate against microorganisms (mean aerodynamic size < 5 microm). These results provide useful pilot data to establish guidelines for respiratory protection against airborne dust and microorganisms on agricultural farms. The method is a promising tool for further epidemiological and intervention studies in agricultural and other similar occupational and nonoccupational environments.

Inhalation of stable dust extract prevents allergen induced airway inflammation and hyperresponsiveness

BACKGROUND

Recent epidemiological studies have shown that growing up on a traditional farm provides protection from the development of allergic disorders such as hay fever and allergic asthma. We present experimental evidence that substances providing protection from the development of allergic diseases can be extracted from dust collected in stables of animal farms.

METHODS

Stable dust was collected from 30 randomly selected farms located in rural regions of the Alps (Austria, Germany and Switzerland). The dust was homogenised with glass beads and extracted with physiological sodium chloride solution. This extract was used to modulate immune response in a well established mouse model of allergic asthma.

RESULTS

Treatment of mice by inhalation of stable dust extract during sensitisation to ovalbumin inhibited the development of airway hyperresponsiveness and airway eosinophilia upon challenge, as well as the production of interleukin 5 by splenocytes and of antigen specific IgG(1) and IgE. Dust extract also suppressed the generation of human dendritic cells in vitro. The biological activity of the dust extract was not exclusively mediated by lipopolysaccharide.

CONCLUSIONS

Stable dust from animal farms contains strong immune modulating substances. These substances can interfere with the development of both cellular and humoral immunity against allergens, thus suppressing allergen sensitisation, airway inflammation, and airway hyperresponsiveness in a murine model of allergic asthma.

Manganese exposures during shielded metal arc welding (SMAW) in an enclosed space

The work reported here evaluates the effectiveness of various rates of dilution ventilation in controlling welder exposures to manganese in shielded metal arc welding (SMAW) fume when working in enclosed or restricted spaces. Personal and area monitoring using total and respirable sampling techniques, along with multiple analytical techniques, was conducted during the welding operations. With 2000 cubic feet per minute (CFM) (56.63 m3/min) dilution ventilation, personal breathing zone concentrations for the welder using 1/8 inches (3.18 mm) E6010 and E7018 mild steel electrodes were within 75% of the existing threshold limit value (TLV of 0.2 mg/m3 for total manganese and were five times greater than the 2001-2003 proposed respirable manganese TLV of 0.03 mg/m3. Manganese concentrations using high manganese content electrodes were five times greater than those for E6010 and E7018 electrodes. Area samples upstream and downstream of the welder using E6010 and E7018 electrodes exceeded 0.2 mg/m3 manganese. Concentrations inside and outside the welding helmet do not indicate diversion of welding fume by the welding helmet from the welder's breathing zone. There was close agreement between respirable manganese and total manganese fume concentrations. Total fume concentrations measured by gravimetric analysis of matched-weight, mixed cellulose ester filters were comparable to those measured via preweighed PVC filter media. This study indicates that 2000 CFM general dilution ventilation per 29 CFR 1910.252 (c)(2) may not be a sufficient means of controlling respirable manganese exposures for either welders or their helpers in restricted or enclosed spaces. In the absence of site-specific monitoring data indicating otherwise, it is prudent to employ respiratory protection or source capture ventilation for SMAW with E6010, E7018, and high manganese content electrodes rather than depending solely on 2000 CFM general dilution ventilation in enclosed spaces.

Biosafety level 3 laboratory for autopsies of patients with severe acute respiratory syndrome: principles, practices, and prospects

BACKGROUND

During the outbreak of the emergent severe acute respiratory syndrome (SARS) infection, >30% of the approximately 8000 infected persons were health care workers. The highly infectious nature of SARS coronavirus (SARS-CoV) compelled our pathologists to consider biosafety issues in the autopsy room and for tissue processing procedures.

METHODS

A specially designed biosafety level 3 (BSL-3) autopsy laboratory was constructed and divided into a clean area, a semicontaminated area, a contaminated area, and 2 buffer zones. High-efficiency particulate air filters were placed in the air supply and exhaust systems. Laminar air flow was from the clean areas to the less clean areas. The negative pressures of the contaminated, semicontaminated, and clean areas were approximately -50 pa, -25 pa, and -5 pa, respectively. Personal protective equipment, including gas mask, impermeable protective clothing, and 3 layers of gloves worn during autopsies; the equipment was decontaminated before it was allowed to exit the facility. Strict BSL-3 practices were followed.

RESULTS

When a given concentration of particulate sarin simulant was introduced into the contaminated area, it could not be detected in either the semicontaminated area or clean area, and particles >0.3 microm in size were not detected in the exhaust air. A total of 16 complete postmortem examinations for probable and suspected SARS were performed during a 2-month period. Of these, 7 reported confirmed cases of SARS. None of the 23 pathologists and technicians who participated in these autopsies was infected with SARS-CoV.

CONCLUSIONS

Our experience suggests that BSL-3 laboratory operating principles should be among the special requirements for performing autopsies of contaminated bodies and that they can safeguard the clinicians and the environment involved in these procedures.

Assessment of personal protective equipment used for facial mucocutaneous exposure protection in nonhuman primate areas

Animal caretakers working in NHP areas must wear facial PPE to protect themselves from the zoonotic hazards related to splash exposures, but PPE that is uncomfortable may present its own risks. The authors evaluated the level of protection offered by several types of facial PPE against a variety of simulated facial mucocutaneous exposures of the sort that could occur during typical procedures in Old World NHP facilities and determined that less restrictive PPE can be used without compromising safety.

Risk of high blood pressure in salt workers working near salt milling plants: a cross-sectional and interventional study

BACKGROUND

Workers working close to salt milling plants may inhale salt particles floating in the air, leading to a rise in plasma sodium, which, in turn, may increase the blood pressure and the risk of hypertension.

METHODS

To test the above hypothesis, occupational health check-up camps were organized near salt manufacturing units and all workers were invited for a free health examination. The workers who worked with dry salt in the vicinity of salt milling plants were defined as "non-brine workers," while those working in brine pans located far away from milling plants were defined as "brine workers." Blood pressure (BP) was measured during each clinical examination. In all, 474 non-brine workers and 284 brine workers were studied.

RESULTS

Mean systolic blood pressure of non-brine workers (122.1 +/- 13.3 mm Hg) was significantly higher than that of brine workers (118.8 +/- 12.8 mm Hg, p < 0.01). Mean diastolic blood pressure of non-brine workers (71.5 +/- 10.4 mm Hg) was significantly higher than that of brine workers (69.7 +/- 9.4 mm Hg, p = 0.02). The prevalence of hypertension was significantly higher in non-brine workers (12.2%) than in brine workers (7.0%, p = 0.02). Nineteen salt workers were monitored while they used face masks and spectacles, for six days. Systolic, as well as diastolic, blood pressure of these workers began declining on the third day and continued to decline on the fourth day, but remained stationary up to the sixth day. The concentration of salt particles in the breathing zone of these workers was 376 mg/m3 air.

CONCLUSION

Inhalation of salt particles in non-brine workers may be an occupational cause of increased blood pressure.

Remediation ofBacillus anthracisContamination in the U.S. Department of Justice Mail Facility

The U.S. Department of Justice (DOJ) mail facility in Landover, Maryland, was contaminated with Bacillus anthracis spores as a result of the 2001 anthrax bioterrorism attacks through the U.S. postal system. Surface environmental sampling within the facility indicated that the contamination was due to receipt of mail that had come in contact with Bacillus anthracis spores from the source letters at the Brentwood postal facility in Washington, DC. The DOJ adopted a two-pronged approach for remediating the facility, using aqueous chlorine dioxide to decontaminate hard, nonporous surfaces and paraformaldehyde to fumigate two pieces of mail equipment. Before the start of the remediation activities, all porous materials were removed from the mail area. Since all postremediation environmental samples were negative for growth of Bacillus anthracis spores, the remediation was judged to be effective. The facility remained closed for almost 4(1/2) months. The cleanup activities took about 2(1/2) months, with source reduction activities being the most time-consuming. Of the seven facilities that performed fumigations to remediate Bacillus anthracis contamination, the DOJ mail facility was the second building to be reopened.

The role of air pollution in asthma and other pediatric morbidities

A growing body of research supports the role of outdoor air pollutants in acutely aggravating chronic diseases in children, and suggests that the pollutants may have a role in the development of these diseases. This article reviews the biologic basis of children's unique vulnerability to highly prevalent outdoor air pollutants, with a special focus on ozone, respirable particulate matter (PM 2.5 [<2.5 microm in diameter] and PM 10 [<10 microm in diameter]), lead, sulfur dioxide, carbon monoxide, and nitrogen oxides. We also summarize understanding regarding health effects and molecular mechanisms of action. Practitioners can significantly reduce morbidity in children and other vulnerable populations by advising families to minimize pollutant exposures to children with asthma, or at a broader level by educating policymakers about the need to act to reduce pollutant emissions. Management of children with asthma must expand beyond preventing exposures to agents that directly cause allergic reactions (and therefore can be diagnosed by means of skin tests) and must focus more attention on agents that cause a broad spectrum of nonspecific, generalized inflammation, such as air pollution.

Evaluation of Misting Controls to Reduce Respirable Silica Exposure for Brick Cutting

It is estimated that more than 1.7 million workers in the United States are potentially exposed to respirable crystalline silica, with a large percentage having been exposed to silica concentrations higher than the limits set by current standards and regulations. The purpose of this study is to characterize the use of water-misting engineering controls to reduce exposure to respirable crystalline silica for construction workers engaged in the task of brick cutting. Since data concerning the efficacy of engineering controls collected at worksites is often confounded by factors such as wind, worker skill level, the experiments were conducted in a laboratory environment. A completely enclosed testing chamber housed the brick-cutting saw. Respirable dust concentrations were measured using the Model 3321 Aerodynamic Particle Sizer. Specifically, the laboratory experiment was designed to compare dust suppression through water misting using conventional freely flowing water techniques. Brass atomizing nozzles with three flow rates were used for making this comparison: low (5.0 ml s(-1) or 4.8 gal h(-1)), medium (9.0 ml s(-1) or 8.6 gal h(-1)) and high (18 ml s(-1) or 17.3 gal h(-1)). The flow rate for freely flowing water, using manufacturer-supplied equipment, was 50 ml s(-1) (48 gal h(-1)). The experiment consisted of five replications of five samples each (low-misting, medium-misting, high-misting, freely flowing water and no control). The order of sampling within each replicate was randomized. Estimates of dust reduction showed that low-misting nozzles reduced the respirable mass fraction of dust by about 63%, medium-misting nozzles by about 67%, high-misting nozzles by about 79% and freely flowing water by about 93%. Based on these results, it may be feasible to use misting to control respirable silica dust instead of freely flowing water. This strategy is of practical interest to the construction industry which must frequently limit the amount of water used on construction sites.

Respiratory demand during rigorous physical work in a chemical protective ensemble

Protection afforded by a respirator filter depends on many factors, among them chemical or biological agent and flow rate. Filtration mechanisms, such as chemical adsorption, depend on sufficient residence time for the filter media to extract noxious agents from the airstream. Consequently, filter efficiency depends on inspiratory air velocities, among other factors. Filter designs account for this by adjusting bed depth and cross-sectional area to anticipated flow rates. Many military and commercial filters are designed and tested at 32-40 L/min. The present study investigated respiratory demand while U.S. Marines (n=32) completed operationally relevant tasks in chemical protective ensembles, including M-40 masks and C2A1 filters. Respiratory demand greatly exceeded current test conditions during the most arduous tasks: minute ventilation=96.4+/-18.9 L/min (mean+/-SD) with a maximum of 131.7 L/min observed in one subject. Mean peak inspiratory flow rate (PIF) reached 238.7+/-34.0 L/min with maximum PIF often exceeding 300 L/min (maximum observed value=356.3 L/min). The observed respiratory demand was consistent with data reported in previous laboratory studies of very heavy workloads. This study is among the few to report on respiratory demand while subjects perform operationally relevant tasking in chemical protective ensembles. The results indicate that military and industrial filters will probably encounter higher flow rates than previously anticipated during heavy exertion.

Laboratory and field evaluation of a new personal sampling system for assessing the protection provided by the N95 filtering facepiece respirators against particles

OBJECTIVES

We have recently developed a new personal sampling system for the real-time measurement of the protection provided by respirators against airborne dust and micro-organisms. The objective of this study was to evaluate the performance characteristics of the new sampling system in both laboratory and field conditions.

METHODS

The measurements were conducted using the N95 filtering facepiece respirators and the newly developed personal sampling system put on a manikin (laboratory study) or donned by a human subject (laboratory and field studies). Two inhalation flow rates (0 and 40 l min(-1)) in conjunction with the sampling flow rate (10 l min(-1)) were tested in the manikin-based experiments to investigate the effects of the leak location (nose, cheek and chin) and the depth of the sampling probe (0, 5, 10 and 15 mm) within the respirator. The effect of human activity on the protection factor was evaluated using a variety of head movements and breathing patterns when a human subject wore the respirator in a room-size laboratory test chamber. The field study was conducted during corn harvesting with a respirator worn by a human subject on a combine.

RESULTS

There was no significant difference in the protection factors for different leak locations, or for sampling probe depths, when the inhalation rate was 0 l min(-1). For the inhalation rate of 40 l min(-1), the protection factors for nose leaks were higher than those for chin and cheek leaks. Furthermore, the protection factor was the lowest and showed the least variation when the sampling probe depth was equal to 0 mm (imbedded on the respirator surface). Human subject testing showed that the grimace maneuver decreased the protection factor and changed the original respirator fit. The protection factor during breath holding was lower than that found during inhalation and exhalation. Field results showed greater variation than laboratory results.

CONCLUSIONS

The newly designed personal sampling system efficiently detected the changes in protection factors in real time. The sampling flow was least affected by the inhalation flow when the sampling probe was imbedded on the respirator surface. Leak location, breathing patterns and exercises did affect the measurement of the protection factors obtained using an N95 filtering facepiece respirator. This can be attributed to the differences in the in-mask airflow dynamics contributed by the leak, filter material, sampling probe and inhalation. In future studies, it would be beneficial if the laboratory data could be integrated with the field database.

Interstitial lung disease: causes, treatment, and prevention

The interstitial lung diseases (ILD) are a diverse group of lung disorders that involve primarily the parenchyma of the lung. Whether idiopathic or secondary to systemic disorders, inhaling exposures, or drugs, they inflame and scar the interstitium of the lungs and obliterate alveoli and capillary units. The scarring or fibrosis produces restrictive lung impairment while destruction of the alveoli, interstitium, and capillaries results in severe gas exchange abnormalities. Clinically, the ILD present subtly with progressive dyspnea on exertion and a dry cough. Rales or crackles on examination prompt chest radiography that may reveal bilateral infiltrates. These infiltrates are often treated as atypical pneumonias that fail to respond to antimicrobial therapy over weeks to months. Because of this and their infrequent presentation in the primary care setting, the diagnosis of ILD is commonly delayed. This paper highlights the natural history of the ILD in general, gives a broad overview of the pathophysiology in these diseases, and encourages greater awareness for the detection of ILD in primary care.

Reducing enclosed cab drill operator's respirable dust exposure with effective filtration and pressurization techniques

Many different types of surface mining equipment use enclosed cabs to protect equipment operators from health and safety hazards. The overburden removal and mining process can be extremely dusty and can cause excessive dust exposure. To study this issue, a cooperative research effort was established between the National Institute for Occupational Safety and Health, U.S. Silica Co., Clean Air Filter Co., and Red Dot Corp. in an effort to lower respirable dust levels in an enclosed cab on an older surface drill at a silica sand operation. Throughout this research effort, a number of modifications were incorporated into the drill's filtration and pressurization system, as well as in other areas, to improve its design and performance. An average cab efficiency of 93.4% was determined with gravimetric sampling instruments when comparing the outside with the inside cab dust levels on the final design. Although this study considered just one operation, the goal was to identify cost-effective improvements that could be implemented on all types of enclosed cabs to lower respirable dust concentrations. Two critical components for an effective enclosed cab system are having a properly designed, installed, and maintained filtration and pressurization system, along with a method for maintaining structural cab integrity, which allows the cab to be positively pressurized. Another important component is maintaining cab cleanliness. Although this research was originally directed toward the mining industry, it is also applicable to agricultural or construction equipment.

Evaluation of skin and respiratory doses and urinary excretion of alkylphosphates in workers exposed to dimethoate during treatment of olive trees

This article describes a study of exposure to dimethoate during spraying of olive trees in Viterbo province in central Italy. Airborne concentrations of dimethoate were in the range 1.5 to 56.7 nmol/m(3). Total skin contamination was in the range 228.4 to 3200.7 nmol/d and averaged 96.0% +/- 3.6% of the total potential dose. Cotton garments afforded less skin protection than waterproof ones, which were in turn associated with higher skin contamination than disposable Tyvek overalls. Total potential doses and estimated absorbed doses, including their maxima, were below the acceptable daily intake of dimethoate, which is 43.6 nmol/kg body weight (b.w.). Urinary excretion of alkylphosphates was significantly higher than in the general population, increasing with exposure and usually showing a peak in the urine sample collected after treatment. Metabolite concentrations were influenced by the type of individual protection used: minimum levels were associated with the closed cabin and maximum levels with absence of any respiratory or hand protection. Urinary alkylphosphates showed a good correlation with estimated absorbed doses and are confirmed as sensitive biologic indicators of exposure to phosphoric esters.

Agglomeration rate and action forces between atomized particles of agglomerator and inhaled-particles from coal combustion

In order to remove efficiently haled-particles emissions from coal combustions, a new way was used to put forward the process of agglomeration and the atomization was produced by the nozzle and then sprayed into the flue before precipitation devices of power station boiler in order to make inhaled-particles agglomerate into bigger particles, which can be easily removed but not change existing running conditions of boiler. According to this idea, a model is set up to study agglomeration rate and effect forces between fly ash inhaled-particles and atomized agglomerator particles. The developed agglomeration rate was expressed by relative particle number decreasing speed per unit volume. The result showed that viscosity force and flow resistance force give main influences on agglomeration effect of inhaled-particles, while springiness force and gravity have little effect on agglomeration effect of theirs. Factors influencing the agglomeration rate and effect forces are studied, including agglomerator concentration, agglomerator flux and agglomerator density, atomized-particles diameters and inhaled-particles diameter and so on.

Exposure to flour dust in UK bakeries: current use of control measures

OBJECTIVES

In May 2001, a maximum exposure limit (MEL) for flour dust was set in the UK at 10 mg/m(3) [8 h time-weighted average (TWA)] with a short-term exposure limit (STEL) of 30 mg/m(3) (15 min reference period). The purpose of this study was to produce a benchmarking baseline of current control measures and exposure levels, in addition to assessing the provision of training and the knowledge of the UK regulations amongst the bakeries.

METHODS

A total of 208 long-term personal inhalable dust samples (8 h TWA) were collected from workers in 55 bakeries (covering a wide range of industry types and sizes) between October 2002 and December 2003 in England, Wales and Scotland. Standardized occupational hygiene reports were produced for each establishment to provide information about the site (such as the size of the bakery) and the control measures employed (including ventilation, good working practices, knowledge of UK regulations and the extent of training provided).

RESULTS

Median inhalable dust exposure (8 h TWA) for the bakery workers was 3.7 mg/m(3) (75th percentile at 7.7 mg/m(3)) and 17% of the dust results exceeded the MEL. Although information about the MEL has been available in the trade press and through recognised trade associations, only 27% of the bakeries were aware of the MEL and STEL. Mixed model regression analysis suggested that determinants of higher exposure included the job category (particularly weighing/sieving or mixing), medium to large bakery size (50 or more employees) and bakeries being located in Scotland. However, having an appointed safety representative was associated with lower exposure.

CONCLUSIONS

The conclusions derived here are based upon the use of a statistical model, but clearly, if bakeries and individuals employ good working practices, with correct use of local exhaust ventilation, they should be able to comply with the MEL.

Application of health promotion theories and models for environmental health

The field of environmental health promotion gained new prominence in recent years as awareness of physical environmental stressors and exposures increased in communities across the country and the world. Although many theories and conceptual models are used routinely to guide health promotion and health education interventions, they are rarely applied to environmental health issues. This article examine show health promotion theories and models can be applied in designing interventions to reduce exposure to environmental health hazards. Using the Community Action Against Asthma (CAAA) project as an example, this article describes the application of these theories and models to an intervention aimed at reducing environmental triggers for childhood asthma. Drawing on the multiple theories and models described, a composite ecological stress process model is presented, and its implications for environmental health promotion discussed.

Reduction of formaldehyde concentrations in the air and cadaveric tissues by ammonium carbonate

The reduction of formaldehyde by ammonium carbonate was examined in cadavers and in vitro. Formaldehyde concentrations in the air (10 cm above human cadavers) and in various cadaveric tissues were measured with or without perfusion of ammonium carbonate solution into formaldehyde-fixed cadavers. Air samples were monitored using Kitagawa gas detector tubes. For measurement of formaldehyde in tissues, muscles and organs were cut into small pieces and tissue fluids were separated out by centrifugation. These specimen fluids were diluted, supplemented with 3-methyl-2-benzothiazolinone hydrazone hydrochloride and quantified by spectrophotometry. In five cadavers without ammonium carbonate treatment, the formaldehyde concentrations in the air above the thorax and in various tissue fluids were 1.2-3.0 p.p.m. and 0.15-0.53%, respectively. Arterial reperfusion of saturated ammonium carbonate solution (1.0, 1.5 or 2.0 L) into five formaldehyde-fixed cadavers successfully reduced the formaldehyde levels, both in the air (0.5-1.0 p.p.m.) and in various tissue fluids (0.012-0.36%). In vitro experiments demonstrated that formaldehyde concentrations decreased, first rapidly and then gradually, with the addition of ammonium carbonate solution into fluids containing formaldehyde. It was confirmed that formaldehyde reacted with the ammonium carbonate and was thereby changed into harmless hexamethylenetetramine. The application of ammonium carbonate solution via intravascular perfusion and, if necessary, by infusion into the thoracic and peritoneal cavities, injection into muscles and spraying on denuded tissues can be anticipated to reduce formaldehyde to satisfactorily low levels in cadaveric tissues and, consequently, in the air, which may provide safe and odorless dissecting rooms.

The efficacy of local exhaust ventilation for controlling dust exposures during concrete surface grinding

This study assessed the effectiveness of a commercially available local exhaust ventilation (LEV) system for controlling respirable dust and crystalline silica exposures during concrete grinding activities. Surface grinding was conducted at six commercial building construction sites in Seattle, WA, by cement masons. Time-integrated filter samples and direct reading respirable dust concentrations were collected using a cyclone in line with a direct reading respirable dust monitor. Personal exposure levels were determined with and without LEV, one sample directly after the other. A total of 28 paired samples were collected in which three different dust collection shroud configurations were tested. Data obtained with a direct reading respirable dust monitor were adjusted to remove non-work task-associated dust exposures and was subsequently used to calculate the exposure reduction achieved. The application of LEV resulted in a reduction in the overall geometric mean respirable dust exposure from 4.5 to 0.14 mg/m(3), a mean exposure reduction of 92%. Despite the effective control of dust generated during surface grinding, 22 and 26% of the samples collected while LEV was being used were greater than the 8 h time-weighted average permissible exposure limit (Occupational Safety and Health Administration) and threshold limit value (American Congress of Governmental Industrial Hygienists) for respirable crystalline silica, respectively.

Proactive approaches for mold-free interior environments

Interior design education and practice can contribute to the prevention of mold growth in indoor environments. The authors provide an overview of current thinking within the interior design educational and professional communities regarding proactive approaches to achieving mold-free building interiors, including identification of current best practices for the prevention of mold problems in buildings. They also discuss the development of certification programs. A review of recent literature points to the need for interior designers to be educated to specify the use of ecologically sound materials that support the health of building occupants. The authors present trade-offs between best practices for designing mold-free indoor environments (including considerations of cost, maintenance, and operation) and occupant comfort, health, and well-being.

Effectiveness of personal protective equipment: relevance of dermal and inhalation exposure to chlorpyrifos among pest control operators

This study assessed the effectiveness of a custom fit personal protective equipment (PPE) program aimed at reducing occupational exposure to pesticides. The intervention study was carried out on 15 pest control operators (PCOs) during mixing/loading and application of chlorpyrifos. Each worker was measured twice; first while the worker used PPE as normal (baseline measurement), and second after making some adjustments to the PPE (postintervention measurement). The applied intervention consisted of a tight-fitting, full-face respirator, fit-testing, long gloves, chemical-proof boots, a Tyvek hood, and an instruction video that was shown prior to putting on the PPE. A comprehensive evaluation program was used for the within-subject comparisons, including assessment of potential dermal exposure, actual dermal exposure, inhalation exposure, and internal dose as measured by the urinary metabolite 3,5,6-trichloro-2-pyridinol (TCP). The PPE program resulted in a significant increase in fit factors from a mean of 670 to 132,000. Actual dermal exposure levels decreased on average by fourfold after implementation of the PPE program (baseline AM = 132.1 microg; postintervention AM = 32.6 microg). The TCP levels in urine collected 24-32 hours after spray activities were lower in the postintervention data set (AM = 21.2 microg TCP/g creatinine vs. AM = 13.9 microg TCP/g creatinine). However, it is impossible to attribute these differences totally to the PPE program since workers had significant and varying urinary TCP levels before onset of spraying activities. Linear regression models showed that dermal exposure was only a predictive parameter for TCP levels in urine in the baseline data set. Although the results should be interpreted cautiously this study suggests a protective effect of the evaluated PPE program.

Propofol Decreases Waste Anesthetic Gas Exposure During Pediatric Bronchoscopy

OBJECTIVE

This study compared the anesthetic gas exposure and operating conditions during insufflation anesthesia with halothane-alone versus halothane-propofol in children undergoing direct laryngobronchoscopy.

STUDY DESIGN

Forty-six children were enrolled in this randomized prospective study, with institutional review board approval and informed consent.

METHODS

All children were anesthetized by halothane mask induction and anesthesia was maintained using spontaneous ventilation with insufflation. No muscle relaxants or opioids were used. In the halothane group, halothane was titrated as needed. In the propofol group, halothane was decreased to 1% inspired concentration and the propofol was titrated as needed to maintain spontaneous ventilation and a still patient. Trace anesthetic gases, hemodynamic stability, and operating conditions were measured.

RESULTS

The groups were similar in age, weight, and bronchoscopy time. There was significantly less gas exposure in the propofol group (25 +/- 33 parts per million) versus the halothane group (66 +/- 97 ppm; P <.02). There was a trend toward earlier emergence in the halothane group (33 +/- 13 minutes) versus the propofol group (41 +/- 17 minutes). Postoperative stridor was common, occurring in 30% of children.

CONCLUSIONS

Insufflation anesthesia with spontaneous respiration provides excellent surgical conditions for laryngobronchoscopy. The addition of propofol resulted in fewer airway complications (P =.047). Although the addition of propofol significantly decreased anesthetic gas exposure in the operating room, both techniques resulted in operating room pollution that exceeded the maximum levels of 2 ppm per hour recommended by the US National Institute for Occupational Safety and Health (NIOSH).

[Filamentous fungi and mycotoxins as potential occupational risk factors among farmers harvesting various crops]

The studies to determine the level of filamentous fungi and mycotoxins were carried out in samples of grain and grain dust during threshing of cereals by a combine harvester. High concentration of fungi was noted in grain and grain dust samples, it ranged from 5.0 to 520.0 cfu/g.10(3) and from 275.0 to 2825.0 cfu/g.10(3), respectively Allergizing and toxigenic fungi of Alternaria, Geotrichum, Cladosporium, Penicillium, Aspergillus and Fusarium species were observed in the study samples of grain and grain dust. In the samples of wheat grain, mycotoxins were also noted: moniliformin (MON), deoxynivalenol (DON) and ochratoxin A (OTA); their concentrations ranged from 0.025 to 0.088 microgram/g; 0.015-0.068 microgram/g; and from 0.0004 to 0.0008 microgram/g, respectively. The level of mycotoxins in the grain dust samples was within the range of 0.025-0.149 microgram/g-MON; 0.015-0.215 microgram/g-DON; 0.015-0.360 microgram/g-NIV; and 0.0004-0.0012 microgram/g-OTA. A significant correlation was observed between the occurrence of fungi of Fusarium species and the concentration of pathologic mycotoxins. The results confirm a considerable occupational risk among farmers engaged in grain threshing due to inhalation of pathogenic species of filamentous fungi and mycotoxins.

[The advance of protection for hazard factor during autopsy]

Recently, the special characteristics of work with SARS require particular attention to the facilities, equipment, policies and procedures involved. In fact, an autopsy also subject prosectors and others to a wide variety of hazards, including bloodborne, aerosolized pathogens and others (for example SARS). Forensic pathologists and other persons in close proximity to an autopsy need personal protective equipment, fourthemore, laboratory procedure and facility design principles of biosafety should be established for the protection of all personnal involved in the work.

Comparison of simulated respirator fit factors using aerosol and vapor challenges

Although not well established, mask leakage measured using submicron aerosol challenges is generally accepted as being representative of vapor challenges. The purpose of this study was to compare simulated respirator fit factors (FFs) measured using vapor challenges to those measured using an aerosol challenge. A full-facepiece respirator was mounted on a headform inside a small enclosure and modified with controlled leaks (laser-drilled orifices) to produce FFs ranging from about 300 to 30,000. A breathing machine was used to simulate breathing conditions of 1.0 L tidal volume and 25 breaths/min. A monodisperse aerosol consisting of 0.72 micron polystyrene latex spheres (PSL) was used for the reference test aerosol, and FFs were measured using a laser aerosol spectrometer. An inert gas, sulfur hexafluoride (SF6), and an organic vapor, isoamyl acetate (IAA), were used as the vapor challenges. The in-mask concentration of SF6 was measured using a gas chromatograph (GC). A GC was also used to quantify in-mask IAA concentration samples actively collected with sorbent tubes. FF measurements made with the PSL aerosol challenge were conducted in sequence with the SF6 and IAA challenges, without disturbing the mask, to yield matched data pairs for regression analysis. FFs measured using the PSL reference aerosol were found to correlate well with those measured with the SF6 (r2 = 0.99) and IAA (r2 = 0.98) vapor challenges. FFs measured using IAA tended to be higher at values below 10,000. The best agreement was observed with the inert gas, SF6. The results of this study suggest that submicron aerosols are suitable as quantitative fit test challenges for assessing the performance of respirators against inert vapors.

Mechanisms of tolerance to inhalant allergens: the relevance of a modified Th2 response to allergens from domestic animals

Subjects can be "non-allergic" because (1) they are not exposed, (2) they fail to make an immune response, or (3) they make an immune response that does not include IgE antibodies (Ab). The recent observation that children raised in a house with a cat are less likely to become allergic to cat allergen than those who only get indirect exposure provides a model to investigate the factors controlling allergic responses. Many of these highly exposed children have made an IgG and IgG4 Ab response to Fel d 1 without IgE Ab, i.e., a "modified Th2 response". In countries where cats are a major cause of asthma, the presence of a cat may decrease the risk of asthma. By contrast, in countries with high exposure to dust mites, cats can induce specific tolerance to Fel d 1 without influencing asthma or the IgE Ab response to dust mites. Using overlapping peptides to investigate T cell responses to Fel d 1 suggests that the structure of the molecule plays a special role in inducing the T cell responses that can "control" the immune response to cat allergens. This T cell response is characterized by high levels of IL-10 production, but this is not restricted to those who have made a modified Th2 response. The results suggest that there are major differences in the immune response to different allergens that profoundly affect their role in allergic disease. Dust mite and cockroach differ from cat (and rat) allergens not only in the quantity inhaled and the particles' sizes but also in the biochemistry of the molecule.

Reducing exposure to laboratory animal allergens

Laboratory animal allergy is a serious health problem. We examined several possible allergen-reducing strategies that might be effective in the working mouse room. Ambient allergen concentrations were measured when mice were maintained under several conditions: conventional housing versus ventilated cage racks operated under negative or positive pressure. We found that housing mice in ventilated cages operated under negative pressure and using ventilated changing tables reduced ambient mouse allergen (Mus m 1) concentrations tenfold, compared with values when mice were housed in conventional caging and using a conventional (non-ventilated) changing table. Housing mice in positively pressurized cages versus conventional cages did not reduce ambient allergen values. Cleaning mouse rooms at an accelerated frequency also did not reduce ambient Mus m 1 concentration. We also quantified ambient allergen values in several areas of The Jackson Laboratory. A facility-wide survey of Mus m 1 concentrations indicated that allergen concentrations were undetectable in control areas, but ranged from a mean (+/- SEM) 0.11 +/- 0.02 ng/m3 to 5.40 +/- 0.30 ng/m3 in mouse rooms with different cage types. The percentage of animal caretakers reporting allergy symptoms correlated significantly with ambient allergen concentrations: 12.9% reported symptoms in the rooms with the lowest allergen concentration (0.14 +/- 0.02 ng/m3), but 45.9% reported symptoms in rooms with the highest concentration (2.3 +/- 0.4 ng/m3). These data indicate that existing technology can significantly reduce exposure to laboratory animal allergens and improve the health of animal caretakers.

Breathless in Los Angeles: the exhausting search for clean air

Population growth and the proliferation of roadways in Southern California have facilitated a glut of mobile air pollution sources (cars and trucks), resulting in substantial atmospheric pollution. Despite successful efforts over the past 40 years to reduce pollution, an alarming set of health effects attributable to air pollution have been described in Southern California. The Children's Health Study indicates that reduced lung function growth, increased school absences, asthma exacerbation, and new-onset asthma are occurring at current levels of air pollution, with sizable economic consequences. We describe these findings and urge a more aggressive effort to reduce air pollution exposures to protect our children's health. Lessons from this "case study" have national implications.

Lipoic Acid as a Potential First Agent for Protection from Mycotoxins and Treatment of Mycotoxicosis

Mycotoxins--toxic substances produced by fungi or molds--are ubiquitous in the environment and are capable of damaging multiple biochemical mechanisms, resulting in a variety of human symptoms referred to collectively as "mycotoxicosis." In fact, mycotoxins mimic multiple xenobiotics, not only with respect to their ultimate damage, but also in their routes of detoxification. This suggests potential therapeutic options for the challenging treatment of mycotoxicosis. In this brief review, the author examines the use of lipoic acid as an example of an inexpensive and available nutrient that has been shown to protect against, or reverse, the adverse health effects of mycotoxins.

Creating Mold-Free Buildings: A Key to Avoiding Health Effects of Indoor Molds

In view of the high costs of building diagnostics and repair subsequent to water damage--as well as the large medical diagnostic and healthcare costs associated with mold growth in buildings--commitment to a philosophy of proactive preventive maintenance for home, apartment, school, and commercial buildings could result in considerable cost savings and avoidance of major health problems among building occupants. The author identifies common causes of mold growth in buildings and summarizes key building design and construction principles essential for preventing mold contamination indoors. Physicians and healthcare workers must be made aware of conditions within buildings that can give rise to mold growth, and of resulting health problems. Timely advice provided to patients already sensitized by exposure to molds could save these individuals, and their families, from further exposures as a result of inadequate building maintenance or an inappropriate choice of replacement housing.

Impact of portable air filtration units on exposure of haematology-oncology patients to airborne Aspergillus fumigatus spores under field conditions

We undertook a one-year study to investigate the impact of the NSA model 7100A/B portable air filtration unit on exposure of haematology-oncology patients to airborne Aspergillus fumigatus spores under field conditions. Weekly measurements for airborne A. fumigatus were conducted in indoor and outdoor air, and surveillance for invasive aspergillosis was based on a combination of ward liaison, targeted chart review and consultation with the medical staff. The mean indoor A. fumigatus counts (8.1 cfu/m3; range, <0.8 to 42 cfu/m3) reflected the fungal load of outdoor air (9.4 cfu/m3; range, <0.8 to 50 cfu/m3), and were reduced by only about one third in rooms with portable air filtration units (5.3 cfu/m3; range, <0.8 to 41 cfu/m3). During the study period, a total of five cases (incidence density, 0.8 per 1000 patient-days) of invasive aspergillosis (one proven case, four suspected cases; case fatality rate 40%) were recorded. None of these five patients was allocated to a room with portable air filtration unit, however, the difference between incidence densities in rooms with and without portable air filtration units was non-significant (Fisher's exact test, P=0.33). Due to the noise level and thermal discomfort, patient compliance with the air filtration units was poor. We conclude that under field conditions this air filtration unit cannot be recommended for prevention of invasive aspergillosis in neutropenic haematology-oncology patients.

Indoor air quality and occupational exposures at a bus terminal

This article presents an assessment of indoor air quality at a bus terminal. For this purpose, field surveys were conducted, and air samples were collected and analyzed for the presence of selected indoor air quality indicators. Mathematical modeling was performed to simulate bus emission rates, occupational exposure, and ventilation requirements to maintain acceptable indoor air quality. A sensitivity analysis based on literature-derived emission rates estimates was conducted to evaluate the effect of seasonal temperature changes within the terminal. Control measures to improve indoor air quality at the terminal are also outlined. While carbon monoxide concentrations were below the corresponding American Conference of Governmental Industrial Hygienists' (ACGIH) standards under normal operating conditions, they exceeded the 8-hr recommended average standard at peak hours and the World Health Organization (WHO) standard at all times. Total suspended particulates levels, on the other hand, were above the 24-hr American Society of Heating, Refrigerating and Air Conditioning Engineers' (ASHRAE) standard. Carbon monoxide emission rates that were estimated using the transient mass balance model correlated relatively well with those reported in the literature. Modeling results showed that the natural ventilation rate should be at least doubled for acceptable indoor air quality. While pollutant exposure levels depended on the individual activity patterns and the pollutant concentration, pollutant emissions rates within the terminal were affected mostly by the temperature with a 20-25 percent variation in carbon monoxide levels due to changes in seasonal temperatures.

Principles of physiology and respirator performance

Several respirator performance criteria are set to satisfy the physiological requirements of the worker. In particular, Ve and PFI must be understood and used appropriately in the design process. Filtration principles and the nature of workplace aerosols must also be understood to determine appropriate test conditions for particulate respirator filters. Current filter test criteria assure that significant aerosol penetration will not occur in the workplace. It is unlikely that existing positive-pressure respirators can assure positive pressure in the breathing zone at all times for all wearers. High, unsustainable work rates and activities such as running in place have been shown to cause negative-pressure excursions under laboratory and workplace conditions. Because these excursions are brief and infrequent for today's respirators, both logic and performance measurements indicate they have a negligible effect on exposure. Filters could no doubt be designed to pass extreme test criteria. Similarly, it may be possible to design positive-pressure respirators to maintain positive pressure 100 percent of the time for all users. However, it is likely that cost and size would increase and comfort could decrease. Further, available evidence demonstrates that today's respirators provide their expected level of protection when properly selected, used, and maintained. As such, there is no demonstrated need for radical design changes.

Air sampling methodology for asphalt fume in asphalt production and asphalt roofing manufacturing facilities: total particulate sampler versus inhalable particulate sampler

In 2000, the American Conference of Governmental Industrial Hygienists (ACGIH(R)) changed its 1971 threshold limit value (TLV) for 8-hour time-weighted average (TWA) exposure to asphalt from 5 mg/m(3) total particulate (generally < or =40 micrometer [microm] diameter) to 0.5 mg/m(3) inhalable particulate (< or =100 microm aerodynamic diameter) as benzene-soluble aerosol. To date, no inhalable particulate sampling method has been standardized and validated for asphalt fume. Furthermore, much of the historical data were collected using total particulate samplers, and the comparability of total versus inhalable size fractions of asphalt fume is not known. Therefore, the present study compared results from two types of asphalt fume samplers: 1) a traditional total particulate sampler with a 37-mm filter in a closed-face cassette with a 4-mm orifice (NIOSH 5042) versus (2) an inhalable particulate sampler designed by the IOM with a 15-mm orifice. A total of 75 simultaneous pairs of samples were collected, including personal and area samples from 19 roofing and asphalt production facilities operated by 7 different manufacturers. Each sample was analyzed for total mass collected and for benzene-soluble mass. Data from the two sampling methods (total versus inhalable) were comparable for asphalt fumes up to an aerosol concentration of 10 mg/m(3). However, we conclude that the traditional total particulate method is preferable, for this reason: The vast majority of asphalt fume particles are <12.5 microm in diameter. The traditional sampler is designed to collect primarily particles < or =40 microm, while the IOM sampler is optimized for collecting particles < or =100 microm. Thus, the traditional sampler is less likely than the IOM sampler to collect the larger-size fraction of airborne particles, most of which are non-asphalt dust.

Prototype sampling system for measuring workplace protection factors for gases and vapors

A prototype sampling system for measuring respirator workplace protection factors (WPFs) was developed. Methods for measuring the concentration of contaminants inside respirators have previously been described; however, these studies have typically involved continuous sampling of aerosols. Our work focuses on developing an intermittent sampling system designed to measure the concentration of gases and vapors during inspiration. This approach addresses two potential problems associated with continuous sampling: biased results due to lower contaminant concentrations and high humidity in exhaled air. The system consists of a pressure transducer circuit designed to activate a pair of personal sampling pumps during inspiration based on differential pressure inside the respirator. One pump draws air from inside the respirator while the second samples the ambient air. Solid granular adsorbent tubes are used to trap the contaminants, making the approach applicable to a large number of gases and vapors. Laboratory testing was performed using a respirator mounted on a headform connected to a breathing machine producing a sinusoidal flow pattern with an average flow rate of 20 L/min and a period of 3 seconds. The sampling system was adjusted to activate the pumps when the pressure inside the respirator was less than -0.1 inch H(2)O. Quantitative fit-tests using human subjects were conducted to evaluate the effect of the sampling system on respirator performance. A total of 299 fit-tests were completed for two different types of respirators (half- and full-facepiece) from two different manufacturers (MSA and North). Statistical tests showed no significant differences between mean fit factors for respirators equipped with the sampling system versus unmodified respirators. Field testing of the prototype sampling system was performed in livestock production facilities and estimates of WPFs for ammonia were obtained. Results demonstrate the feasibility of this approach and will be used in developing improved instrumentation for measuring WPFs.

Dust control measures in the construction industry

Quartz is a human carcinogen and a causative agent of silicosis. Exposure levels often exceed exposure limits in the construction industry. The need for effective control measures is high, but the complex structure of the construction industry, the variability in sources of exposure and the frequent changes of worksite makes it difficult to implement even simple and potentially effective control measures. The aim of this study was to evaluate the impact of control measures for reducing quartz dust exposure and to assess the extent of their use. Full-shift respirable dust measurements (n = 61) and short-term measurements among construction workers were performed and results of a questionnaire study among 1335 construction workers were analysed. Full-shift measurements showed respirable quartz exposure levels up to 63 times the maximum allowable concentration (MAC) value (0.075 mg/m(3)). More than half of the measurements were above the MAC value. Control measures were not very strongly associated with the full-shift exposure estimates, but the short-term measurements showed large reduction factors (>70%) when wet dust suppression or local exhaust ventilation was used. The effectiveness of control measures is potentially high, and a significant part of the construction worker population is indeed using them on a regular basis. Still, both the exposure study and questionnaire survey show that the use of respiratory protection is the most widely used preventive measure in the construction industry. Respiratory protection might not always reduce exposure sufficiently. Only the combined use of more than one control measure can reduce exposures to acceptable levels.

Determination of known exhalation valve damage using a negative pressure user seal check method on full facepiece respirators

A negative pressure user seal check (NPUSC) method was evaluated for its ability to adequately detect known exhalation valve leakage into a respirator. Three valves with different types of damage were included. Twenty-six test subjects, wearing full facepiece respirators, were asked to perform a NPUSC. Their responses as to whether they passed or failed the user seal check were compared to fit testing results from two quantitative fit test methods: ambient aerosol and controlled negative pressure. In addition, equipment developed at the University of Cincinnati was used to measure in-mask pressures that are generated during the performance of NPUSCs. This technique was employed to assess the ability of respirator wearers to properly conduct user seal checks. The data were analyzed to determine if the user seal check procedure is an effective method for detecting known exhalation valve damage. All test subjects reported passing the user seal check with the undamaged valve. With the warped valve installed, 95 percent of test subjects reported passing the user seal check. With the slit valve installed, 73 percent of test subjects reported passing. With the dirty valve installed, 65 percent reported passing. All fit factors, measured with the damaged valves, were below the Occupational Safety and Health Administration-recognized pass/fail criteria except one fit test with the respirator equipped with the slit valve. Results from the in-mask pressure measurements confirmed whether or not the subject properly conducted a user seal check, but did not detect respirator leakage. In conclusion, the performance of a NPUSC rarely helped to identify damaged exhalation valves. These results support the need for respirator inspection prior to donning with periodic fit testing and the performance of user seal checks as necessary components of an adequate respiratory protection program.