Non-occupational Environments Research Articles

An updated review of diffuse mesothelioma of the pleura – A sentinel health event of potential elongate mineral particle pathogenicity

There are approximately 400 inorganic minerals in the Earth's crust, some of which can be encountered as elongate mineral particles [EMPs] with dimensional characteristics similar to the six minerals known as asbestos and other asbestiform amphiboles with established human pathogenicity. In addition, the rapidly developing field of nanotechnology is producing an ever-increasing array of high aspect ratio engineered nanomaterials [HARNs] with physical dimensions and biodurability similar to the asbestos fiber types with recognized pathogenic potential. Many of these non-asbestos/non-asbestiform EMPs and HARNs with the potential for aerosolization into the breathing zones of workers and in individuals in non-occupational environments have not yet been thoroughly studied with respect to their potential human pathogenicity, a fact which obviously poses concerns for both occupational health and public health professionals. On the basis of dose-response considerations it seems reasonable to infer that if any of these non-regulated EMPs or HARNs actually are pathogenic, then those mineral fiber exposure-induced disorders associated with the lowest cumulative exposure doses of the commercial amphibole types of asbestos, that is, diffuse mesothelioma of the pleura, and its non-malignant correlate of benign parietal pleural plaques, are those which are most likely to occur following inhalational exposures to any of the non-regulated EMPs and HARNs. Because of that observation, this paper reviews certain aspects of diffuse mesothelioma, including a summary of recent changes in the nomenclature of diffuse mesothelioma of the pleura; of both the descriptive and the analytical epidemiology of the disease; of the etiologies of mesothelioma, both “exposure” related and endogenous in nature; and of the asbestos population attributable fraction for diffuse mesotheliomas in the USA, both historically and in the future.

Environmental exposure to manganese and health risk assessment from personal sampling near an industrial source of airborne manganese

Manganese (Mn), despite being a trace element necessary in small quantities for the correct functioning of the organism, at higher concentrations can induce health disorders, mainly in motor and cognitive functions, even at levels found in non-occupational environments. For this reason, US EPA guidelines define safe reference doses/concentrations (RfD/RfC) for health.In this study, the individualised health risk of exposure to Mn through different media (air, diet, soil) and routes of entry into the organism (inhalation, ingestion and dermal absorption) was assessed according to the procedure defined by the US EPA. Calculations related to Mn present in ambient air were made on the basis of data obtained from size-segregated particulate matter (PM) personal samplers carried by volunteers recruited in a cross-sectional study conducted in the Santander Bay (northern Spain), where an industrial source of airborne Mn is located.Individuals residing in the vicinity of the main Mn source (within 1.5 km) were found to have a hazard index (HI) higher than 1, indicating that there is a potential risk for these subjects to develop health alterations. Also, people living in Santander, the capital of the region, located 7–10 km from the Mn source, may have some risk (HI > 1) under some wind conditions (SW). In addition, a preliminary study of media and routes of entry into the body confirmed that inhalation of PM2.5-bound Mn is the most important route contributing to the overall non-carcinogenic health risk related to environmental Mn.

Risk of exposure to acrylamide.

Acrylamide is a toxic compound that can be found it both occupational and non-occupational environments. This study focuses on its sources and health effects of its exposure. Adverse effects of acrylamide, especially carcinogenic, genotoxic, and teratogenic were reported in many studies conducted on animals. Neurotoxicity was reported in workers exposed to acrylamide in the occupational environment. Another important source of populations' exposure to acrylamide is their nutrition. This study focuses on humans' exposure to acrylamide from various sources and its harmful effects on their health. Dietary intake of acrylamide, as well as occupational exposure, cigarette smoking, cosmetics usage and other environmental sources could have a significant effect on human health.

Correlation between reduced work speed and noise annoyance due to exposure to low-frequency noises

Aim: Low-frequency sounds are generated from many sources in both the occupational and nonoccupational environments. Hence, the aim of this study was to investigate the effect of low-frequency noise (LFN) on the working speed and the rate of annoyance of the subjects under study. Materials and Methods: This cross-sectional/interventional study was performed in the sound and vibration laboratory of Isfahan University of Medical Sciences in 2019. Simple random sampling was used to select the subjects. In this study, the working speed of the subjects was evaluated using mental arithmetic test and the rate of the perceived annoyance was measured using ISO 15666 in Likert format (0–11) due to exposure to noise sources. Mann–Whitney U-test was used to analyze the data. Results: There was a significant statistical difference in the rate of the individuals' working speed Between 0 and 90 min at the frequency of 125 Hz and the sound level of 95 dB (P = 0.029). There was a statistically significant difference between the frequencies of 125 and 1000 Hz at the sound pressure level of 85 dB and the 45 min time (P = 0.001) and 90 min (P = 0.001) as well as at the 95 dB sound pressure level at 45 min (P = 001) and 90 min (P = 0.001). Conclusion: The results of the present study showed that increasing sound pressure levels and the exposure time in both LFN and high-frequency noises, increased the working speed and the amount of perceived annoyance in individuals.

An assessment of environmental and toxicological risk to pesticide exposure based on a case-based approach to computing

Pesticide environmental fate and toxicity depends on its physical and chemical features, the soil composition, soil adsorption, as well as residues that may be found in different soil slots. Indeed, pesticide degradation in soil may be influenced by either biotic or abiotic factors. In addition, the toxicity of pesticides for living organisms depends on their adsorption, distribution, biotransformation, dissemination of metabolites together with interaction with cellular macromolecules and excretion. Biotransformation may result in the formation of less toxic and/or more toxic metabolites, while other processes determine the balance between toxic and a nontoxic upcoming. Aggregate exposure and risk assessment involve multiple pathways and routes, including the potential for pesticide residues in food and drinking water, in addition to residues from pesticide use in residential and non-occupational environments. Therefore, this work will focus on the development of a decision support system to assess the environmental and toxicological risk to pesticide exposure, built on top of a Logic Programming approach to Knowledge Representation and Reasoning, complemented with a Case Based attitude to computing. The proposed solution is unique in itself, once it caters for the explicit treatment of incomplete, unknown, or even self-contradictory information, either in terms of a qualitative or quantitative setting.

Lung-deposited surface area concentration measurements in selected occupational and non-occupational environments

Previous experimental and epidemiologic studies suggested that exposure to ultrafine particles (UFP) may result in adverse health effects. Metrics such as the number-concentration and especially the surface-area or lung-deposited surface area (LDSA) appear to be appropriate metrics of dose for predicting pulmonary inflammation of insoluble and poorly soluble ultrafine particles. Currently not much data including LDSA concentrations is available. The aim of this study was therefore to measure LDSA concentrations in a variety of occupational and non-occupational environments as well as in chamber tests. To this end, novel handheld online-monitors were deployed and evaluated for their suitability to be used in a variety of micro-environments and under different conditions. Chamber emissions tests included incense and candle burning, 3D printing and cigarette/e-cigarette smoking. The LDSA concentration was measured in occupational environments such as a canteen kitchen, a welding workshop and in a car. Measurements were also conducted in a private house with a wood-burning stove and with ongoing parallel cooking activities. Depending on the type of micro-environment, the ongoing activities or the material investigated in the chamber-tests, large differences were observed in terms of measured LDSA concentrations, some exceeding up to 1000 times that of the baseline concentration detected before activities initiated. In some of the investigated environments LDSA concentrations were measured for the first time. The data might therefore serve as reference for future studies. The handheld instrument used to measure this data worked well both for stationary measurements as well as for personal monitoring and proved to be an alternative to bulkier benchtop instruments.

Airborne peptidoglycans as a supporting indicator of bacterial contamination in a metal processing plant.

The aim of this study was to assess exposure to airborne endotoxins and peptidoglycans (PGs) as well as possibility of using PGs as a surrogate measure of bacterial exposure in workplaces in a metal processing plant. Personal dosimetry (N = 11) was used to obtain data on concentrations of viable bacteria, total number of bioaerosol particles, endotoxins and peptidoglycans. To investigate the size distributions of aerosol particles responsible for transport of endotoxins and PGs, air samples (N = 5) were additionally collected using the 8-stage cascade impactor. Endotoxins and PGs were assayed with the Limulus amebocyte lysate (LAL) test and a kinetic version of the silkworm larvae plasma (SLP) test, respectively. Median concentrations of airborne PGs (14.6 ng/m3), endotoxins (0.2 ng/m3), viable bacteria (1.16×103 CFU/m3) and the total number of bioaerosol particles (1.81×106 cells/m3) were determined. Qualitative analysis revealed presence of 19 bacterial species belonging to 14 genera. The calculations showed strong, significant correlations (p < 0.05) between endotoxins, viable bacteria (r = 0.75) and the total number of bioaerosol particle concentrations (r = 0.76) as well as between PGs and the total number of bioaerosol particle concentrations (r = 0.72). Size distribution analysis showed that the highest concentrations of bacterial aerosols occurred in the range of 2.1-3.3 μm. In the case of endotoxins, an increase of concentrations in 2 ranges of aerodynamic diameters: 1.1-3.3 μm and 5.8-9 μm was shown. For PGs there was a visible gradual increase of their concentrations in the range 2.1-9 μm. Peptidoglycans can be treated as a supporting indicator of bacterial contamination in metal processing plants, particularly when an assessment of an immunotoxic potential of microbiological hazards needs to be performed. However, to be extrapolated to other occupational and non-occupational environments, the obtained results require a further verification.

Aggregate Exposure and Cumulative Risk Assessment—Integrating Occupational and Non-occupational Risk Factors

Occupational exposure limits have traditionally focused on preventing morbidity and mortality arising from inhalation exposures to individual chemical stressors in the workplace. While central to occupational risk assessment, occupational exposure limits have limited application as a refined disease prevention tool because they do not account for all of the complexities of the work and non-occupational environments and are based on varying health endpoints. To be of greater utility, occupational exposure limits and other risk management tools could integrate broader consideration of risks from multiple exposure pathways and routes (aggregate risk) as well as the combined risk from exposure to both chemical and non-chemical stressors, within and beyond the workplace, including the possibility that such exposures may cause interactions or modify the toxic effects observed (cumulative risk). Although still at a rudimentary stage in many cases, a variety of methods and tools have been developed or are being used in allied risk assessment fields to incorporate such considerations in the risk assessment process. These approaches, which are collectively referred to as cumulative risk assessment, have potential to be adapted or modified for occupational scenarios and provide a tangible path forward for occupational risk assessment. Accounting for complex exposures in the workplace and the broader risks faced by the individual also requires a more complete consideration of the composite effects of occupational and non-occupational risk factors to fully assess and manage worker health problems. Barriers to integrating these different factors remain, but new and ongoing community-based and worker health-related initiatives may provide mechanisms for identifying and integrating risk from aggregate exposures and cumulative risks from all relevant sources, be they occupational or non-occupational.

Fibers as carriers of microbial particles

The aim of the study was to assess the ability of natural, synthetic and semi-synthetic fibers to transport microbial particles. The simultaneously settled dust and aerosol sampling was carried out in 3 industrial facilities processing natural (cotton, silk, flax, hemp), synthetic (polyamide, polyester, polyacrylonitrile, polypropylene) and semi-synthetic (viscose) fibrous materials; 2 stables where horses and sheep were bred; 4 homes where dogs or cats were kept and 1 zoo lion pavilion. All samples were laboratory analyzed for their microbiological purity. The isolated strains were qualitatively identified. To identify the structure and arrangement of fibers that may support transport of microbial particles, a scanning electron microscopy analysis was performed. Both settled and airborne fibers transported analogous microorganisms. All synthetic, semi-synthetic and silk fibers, present as separated threads with smooth surface, were free from microbial contamination. Natural fibers with loose packing and rough surface (e.g., wool, horse hair), sheaf packing and septated surface (e.g., flax, hemp) or present as twisted ribbons with corrugated surface (cotton) were able to carry up to 9×10(5) cfu/g aerobic bacteria, 3.4×10(4) cfu/g anaerobic bacteria and 6.3×10(4) cfu/g of fungi, including pathogenic strains classified by Directive 2000/54/EC in hazard group 2. As plant and animal fibers are contaminated with a significant number of microorganisms, including pathogens, all of them should be mechanically eliminated from the environment. In factories, if the manufacturing process allows, they should be replaced by synthetic or semi-synthetic fibers. To avoid unwanted exposure to harmful microbial agents on fibers, the containment measures that efficiently limit their presence and dissemination in both occupational and non-occupational environments should be introduced.

Role of clothing in both accelerating and impeding dermal absorption of airborne SVOCs.

To assess the influence of clothing on dermal uptake of semi-volatile organic compounds (SVOCs), we measured uptake of selected airborne phthalates for an individual wearing clean clothes or air-exposed clothes and compared these results with dermal uptake for bare-skinned individuals under otherwise identical experimental conditions. Using a breathing hood to isolate dermal from inhalation uptake, we measured urinary metabolites of diethylphthalate (DEP) and di-n-butylphthalate (DnBP) from an individual exposed to known concentrations of these compounds for 6 h in an experimental chamber. The individual wore either clean (fresh) cotton clothes or cotton clothes that had been exposed to the same chamber air concentrations for 9 days. For a 6-h exposure, the net amounts of DEP and DnBP absorbed when wearing fresh clothes were, respectively, 0.017 and 0.007 μg/kg/(μg/m(3)); for exposed clothes the results were 0.178 and 0.261 μg/kg/(μg/m(3)), respectively (values normalized by air concentration and body mass). When compared against the average results for bare-skinned participants, clean clothes were protective, whereas exposed clothes increased dermal uptake for DEP and DnBP by factors of 3.3 and 6.5, respectively. Even for non-occupational environments, wearing clothing that has adsorbed/absorbed indoor air pollutants can increase dermal uptake of SVOCs by substantial amounts relative to bare skin.

Ambient monitoring of airborne asbestos in non-occupational environments in Tehran, Iran

Airborne asbestos fiber concentrations were monitored in the urban areas of Tehran, Iran during the period of 23 August to 21 September 2012. The airborne fiber concentrations of 110 air samples collected from 15 different sites in five regions of Tehran. The monitoring sites were located 2.5 m above ground nearby the main street and heavy traffic jam. The ambient air samples were analyzed using scanning electron microscopy (SEM), with energy-dispersive X-ray analysis and phase-contrast optical microscopy (PCM). The geometric means of the airborne asbestos fiber concentrations in the outdoor living areas was 1.6 × 10−2 SEM f ml−1 (1.18 × 10−3 PCM f ml−1). This criteria is considerably higher than those reported for the levels of asbestos in outdoor living areas in the Europe and the non-occupational environment of the Korea. No clear correlation was found between asbestos fiber concentration and the relative humidity and temperature. The SEM and PLM analysis revealed that all samples examined contained only chrysotile asbestos. It can be concluded that several factor such as heavy traffic, cement sheet and pipe consumption of asbestos, and geographical conditions play an important role for the high airborne asbestos levels in the non-occupational environments.

Hearing protection devices: The regulatory journey to change.

The regulation for the labeling of hearing protection devices (40 CFR Part 211, Subpart B) was promulgated in 1979 and has been the directive for 30 years. During this time, there have been significant changes in the industry with respect to newly developed products, which has resulted in the demand for various types of hearing protectors and an increased awareness of hearing loss in both occupational and non-occupational environments. The foundation of the newly proposed regulation of August 5, 2009 is based on these observations and those that were presented by industry, hearing conservation professionals, and the general public during the EPA Workshop on Hearing Protection Devices that was held in March 2003. While these observations will serve as the backdrop of the presentation, the scenery will be the key elements of the proposed regulation, such as the testing methodology, noise reduction rating range, label format and content, recurrent testing, and reporting requirements of testing data. The audience will journey through these scenic elements but will be delivered to its final destination, which are regulatory change and the prospects of withstanding another 30 years.

Cognitive impairment in an adult Mexican population non-occupationally exposed to manganese

We examined the association between non-occupational exposure to Mn and cognitive functions. The study was carried out in a mining district located in Hidalgo State, Mexico, with 288 adults. Air and blood Mn concentrations were determined, and neuropsychological tests were administered to explore cognitive functions and depression. Blood Mn mean was 9.5 ± 4.14 μg/L. A total of 73% of the study group were in contact with air Mn levels that surpassed the EPA recommended guideline level for non-occupational environments (0.05 μg/m 3). Air Mn concentration was associated as a risk factor for attention impairment (OR = 1.75, 95% CI: 1.01–3.06). Blood Mn levels were not associated to any of the measured outcomes. The main finding of this study is the presence of attention impairments associated to high levels of air Mn exposure. These results confirm previous studies, in which cognitive impairment is reported for exposed population.

Assessment of airborne asbestos fiber concentrations in urban area of Tehran, Iran

Air quality in ambient outdoor air has seldom been evaluated in Iran. Accordingly, we evaluated airborne asbestos fiber concentrations in the urban environment of Tehran, Iran between January 2006 and March 2007. The airborne fiber concentrations of 80 air samples collected from 40 different sites in five areas of Tehran were analyzed by energy-dispersive X-ray analysis in combination with phase-contrast optical microscopy (PCM) and scanning electron microscopy (SEM). The geometric means of the airborne asbestos fiber concentrations were 3.4 × 10−3 PCM f/ml (0.1 SEM f/ml) and 3.3 × 10−3 PCM f/ml (0.20 SEM f/ml) according to areas and seasons, respectively. There were significant differences in the asbestos fiber concentrations between the areas and seasons (p = 0.02; p = 0.04), respectively. In the areas, the average concentration was 3.4 × 10 −3 PCM f/ml (0.1 SEM f/ml), which is considerably higher than those reported for the levels of asbestos in outdoor air in the USA and the urban environment of the Europe. The SEM analyses revealed that the fibrous particles consisted, approximately, of chrysotile (60%), tremolite (10%), anthophyllite (10%), and non-asbestos fibers (20%). We conclude that the high volume of traffic, industrial consumption of asbestos, and geographical and climate conditions are responsible for the high airborne asbestos levels in non-occupational environments in Tehran. Thus, it is to be expected that inhabitants of Tehran will suffer negative health effects due to exposure to asbestos airborne fibers.

Unmetabolized VOCs in Urine as Biomarkers of Low Level Exposure in Indoor Environments

This study aimed to test the possible use of unmetabolized volatile organic compounds (VOCs) in urine as biomarkers of low-level indoor environmental exposure. Twenty-four subjects in 13 dwellings in a prefecture of Japan participated in this study. Air samples of the breathing zone were collected in the living room and bedroom, along with spot urine samples (before bedtime and first morning voids). Toluene, ethylbenzene, xylene isomers, styrene and p-dichlorobenzene in the air and urine samples were measured by gas chromatography/mass spectrometry. For the 21 subjects without solvent exposure at work, there were significant correlations between the time-weighted average air concentrations in the bedroom and morning urinary concentrations for toluene, o-xylene, total xylene and p-dichlorobenzene (correlation coefficients of 0.54, 0.61, 0.56 and 0.84, respectively). Multiple linear regression analysis showed only air VOCs in the bedroom influenced the morning urinary VOC concentrations. We concluded that unmetabolized VOCs in the urine can provide a reliable biological indicator for air VOC exposures in non-occupational environments.

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 μm particles to 270 for 5–10 μm 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 μm) 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 μm). 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.

A positive chemical ionization GC/MS method for the determination of airborne ethylene glycol and propylene glycols in non-occupational environments

An analytical method for ethylene glycol and propylene glycols has been developed for measuring airborne levels of these chemicals in non-occupational environments such as residences and office buildings. The analytes were collected on charcoal tubes, solvent extracted, and analyzed by gas chromatography-mass spectrometry using a positive chemical ionization technique. The method had a method detection limit of 0.07 microg m(-3) for ethylene glycol and 0.03 microg m(-3) for 1,2- and 1,3-propylene glycols, respectively, based on a 1.44 m3 sampling volume. Indoor air samples of several residential homes and other indoor environments have been analyzed. The median concentrations of ethylene glycol and 1,2-propylene glycol in nine residential indoor air samples were 53 microg m(-3) and 13 microg m(-3) respectively with maximum values of 223 microg m(-3) and 25 microg m(-3) detected for ethylene glycol and 1,2-propylene glycol respectively. The concentrations of these two chemicals in one office and two laboratories were at low microg m(-3) levels. The maximum concentration of 1,3-propylene glycol detected in indoor air was 0.1 microg m(-3).

Airborne Asbestos and Non-Asbestos Fiber Concentrations in Non-Occupational Environments in Korea.

Both airborne asbestos and non-asbestos fiber concentrations were evaluated in Korean non-occupational environments. The airborne fiber concentrations were analyzed in 96 air samples, from 48 different points, by transmission electron microscopy, with energy-dispersive X-ray analysis. The geometric means of the airborne asbestos and non-asbestos fiber concentrations were 0.62 and 67.86, and 0.30 and 17.47 fibers/liter in urban and rural areas, respectively. There were significant differences in both the airborne asbestos and non-asbestos fiber concentrations between the urban and rural areas (p<0.05). The geometric means of airborne asbestos and non-asbestos fiber concentrations were 0.67 and 37.93, and 0.27 and 30.67 fibers/liter at the points less than 10 m and more than 30 m away from highways, respectively. The airborne asbestos concentrations were significantly higher at the points less than 10 m away than at the points more than 30 m away from highways (p<0.01).

An Improved Method for the Determination of 1,3-Butadiene in Nonoccupational Environments

Despite health concerns regarding exposure to 1,3-butadiene, there is a dearth of validated methods for its determination in nonoccupational environments. A sampling and analytical methodology is validated for determining 1,3-butadiene in such environments. Samples were collected via sorbent tubes containing 1000 mg of Carbopack B and 150 mg of Carbosieve SIII and analyzed by TD (thermal desorption)-GC/MS. This sorbent combination was compared to that of 600 mg of Carboxen 569. When sampling for 2 h at 30 mL min-1, 20 °C and relative humidity 60%, Carbopack B/Carbosieve SIII gave 1,3-butadiene recoveries >95%, compared to ca. 60% for Carboxen 569. The combined sampling and analytical precision of Carbopack B/Carbosieve III was 13% at 0.17 μg m-3, with a detection limit <0.16 μg m-3. Optimum sampling conditions were as follows: duration 2 h, flow rate 30 mL min-1, maximum temperature 35 °C. The impact on sampling efficiency of ozone concentrations and relative humidity was negligible. Simultaneous samplin...

Environmental and occupational exposure to manganese: a multimedia assessment

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic additive used in Canada since 1976 as an anti-knock agent in unleaded gasoline. Its combustion leads to the emission of Mn oxides, especially Mn3O4. Since no study has assessed the potential risk of chronic exposure to low concentrations resulting from these emissions, the present investigation was undertaken to assess the level of environmental and occupational exposure of the human population. The multimedia exposure of two groups of workers (garage mechanics and blue-collar workers) potentially exposed to different levels of Mn from the combustion of MMT was assessed using personal air samplers, a dietary compilation, water samples at their places of residence, an epidemiological questionnaire and blood and hair samples. Results show that garage mechanics were exposed on average to higher atmospheric Mn at work (0.42 microgram/m3) than the blue-collar workers (0.04 microgram/m3). However, the contribution of atmospheric Mn to the total absorbed dose was less than 1%, and well below the standards established for occupational or environmental exposure; food contributes more than 95% of the multimedia dose. The average whole blood Mn concentrations were similar for the two groups (0.67-0.76 microgram/100 ml) and fall within the normal adult range. The average hair Mn concentrations were significantly higher for the garage mechanics (0.66 microgram/g) than for the blue-collar workers (0.39 microgram/g). The contribution of exogenous Mn versus endogenous Mn is questioned. As judged by the governmental standards or criteria for occupational and non-occupational environments, the current Mn levels in food, water and air may not cause any problems for the workers.