A proposed approach for setting occupational exposure limits for sensory irritants based on chemosensory models

OBJECTIVES: Setting occupational exposure limits (OELs) for odorous or irritating chemicals is a global occupational health challenge. However, often there is inadequate knowledge about the toxicology of these chemicals to set an OEL and their irritation potencies are usually not recognized until they are manufactured or used in large quantities. METHODS: In this paper, the importance of accounting for risk perception and communication; conditioned responses; and interindividual variability in tolerance, detection and susceptibility with respect to setting an OEL are discussed in relation to three chemosensory models. These parameters and models were then used to construct a flowchart-style methodology that can be used to set an OEL for a specific chemical. RESULTS: The OEL identified for a chemical odorant or irritant will depend on the type of chemosensory effect that the chemical is likely to exhibit. For example, experience has shown that chemicals with a low odor threshold often require low OELs even though many are not toxic or do not cause irritation at those air concentrations. CONCLUSION: In order to establish the appropriate OEL, organizations need to agree upon the percentage of the workforce that they are attempting to protect and the types of toxicological end points that are sufficiently important to protect against (e.g. transient eye irritation, enzyme induction or other reversible effects). This is particularly true for sensory irritants. The method described in this paper could also be extended to setting limits for ambient air contaminants where risk perception plays a dominant role in whether the public views the exposure as being reasonable or safe.     

The influence of cognitive bias on the perceived odor, irritation and health symptoms from chemical exposure

 Objective: Responses to volatile chemicals are often subjective and variable, both over time and across individuals. Although variability can derive from differences in individual olfactory sensitivity, the response to a chemical stimulus is also influenced by the complex environment surrounding the exposure, which can include the perceiver’s cognitive state. To explore the role of cognitive bias in chemical exposures, we evaluated whether information about the consequences of exposure to acetone could influence ratings of odor and irritation during exposure and/or the frequency or intensity of reported health symptoms following exposure. Methods: Ninety adults (mean age 33.7, range 25–64) with no history of occupational exposure to solvents, were exposed to 800 ppm acetone in a chamber for 20 min. To control for non-specific responses to the odor of acetone, the subjects were also exposed for 20 min to 200 ppm phenylethyl alcohol (PEA), a nonirritant volatile chemical that produces a distinct odor but does not elicit irritation in the vapor phase. Subjects were assigned to one of three groups (n=30/group); each group was given either a positive, negative or neutral bias towards the consequences of exposure to the chemicals in the study. During exposure, subjects rated the intensity of odor and irritation; following exposure, they completed symptom questionnaires. Results: During the 20-min exposure to acetone, the positive bias group exhibited the most adaptation to its odor and the lowest perceived irritation; following exposure they reported the fewest health symptoms. In contrast, the negative bias group rated higher levels of odor intensity and, on average, reported the most overall irritation; following exposure they reported significantly more health symptoms than the other groups. None of the demographic variables studied (e.g., age, gender, race, smoking status) were predictive of the response to odor or irritation. The perceived irritancy of acetone was well predicted by a linear combination of the perceived odor of acetone and the perceived irritation from PEA (the nonirritant), r ²=0.73. Conclusions: The results provide strong evidence that both the perceived odor and cognitive expectations about a chemical can significantly affect how individuals respond to it. Moreover, because naive control subjects appear to exhibit extreme variation in their cognitive evaluations of chemical effects, there may be limited value in using non-exposed controls to assess the irritancy of chemicals for worker populations. Received: 7 May 1996/Accepted: 20 September 1996     

Odor, irritation and perception of health risk

OBJECTIVES: Understanding the potential for volatile chemicals to elicit chemosensory irritation in the upper respiratory tract is critical to setting occupational exposure limits that are protective of comfort and well-being for the majority of workers. However, the determination of irritant potency for any volatile chemical has been limited by the lack of reliable and non-invasive assays for studying sensory irritation in humans and a failure to appreciate the many non-sensory factors that can influence the reactions to an odor or an irritant in the workplace. METHODS: This paper reviews the issues involved in distinguishing and measuring sensations of odor and irritation from volatile chemicals, and describes recent developments in psychophysical methods for evaluating chemical irritancy in humans, and discusses some of the many non-sensory factors such as exposure history, attitudes and expectations and personality variables that can significantly alter the perception of odor, irritation and health risk following exposure to a volatile chemical. RESULTS: The availability of safe, non-invasive assays to measure directly odor and irritant responses in the species of interest, humans, can both simplify and improve accuracy in the process of developing appropriate occupational exposure guidelines. CONCLUSIONS: Objective measures of irritation onset obtained in conjunction with subjective responses can lend valuable input to the decision process for determining occupational exposure limits but should always account for other factors (e.g., cognitive or emotional) that may be modulating the subjective response.     

Perceived odor,irritation, and health symptoms following short-term exposure to acetone

The subjectivity of irritancy judgments can bias attempts to establish exposure guidelines that protect individuals from the sensory irritation produced by volatile chemicals. At low to moderate chemical concentrations, naive and occupationally exposed individuals often show considerable variation in the reported levels of perceived irritation. Such variation could result from differences in exposure history, differences in the perceived odor of a chemical, or differences in generalized response tendencies to report irritation, or response bias. Thus, experimental evaluation of sensory irritancy must dissociate sensory irritation from response bias. To this end, judgments of perceived irritation from 800 ppm acetone were obtained from acetone-exposed workers and age- and gender-matched naive controls. To assess the role of response bias during exposure to odorants, subjects were also exposed to phenylethyl alcohol (PEA), an odorant that does not produce sensory irritation. Following exposure, subjects completed a subjective symptom survey that included symptoms that have been associated with long-term solvent exposures and symptoms that have not. Acetone-exposed workers and naive controls reported large differences in the perceived intensity of odor and irritation from acetone, yet no differences in the perception of PEA. However, for both groups, the most significant factors mediating reported irritancy and health symptoms from acetone were the perceived intensity of its odor and an individual's bias to report irritation from PEA. The perception of odor intensity and degree of response bias will differ between and within groups of exposed and naive individuals; hence, an assessment of the influence of these factors in experimental and workplace studies of chemical irritancy is warranted. Am. J. Ind. Med. 31:558–569, 1997. © 1997 Wiley-Liss, Inc.     

From chemosensory thresholds to whole body exposures—experimental approaches evaluating chemosensory effects of chemicals

Objectives: To ensure safety and health the avoidance of adverse chemosensory effects is essential at workplaces where volatile chemicals are used. The present study describes psychophysical approaches that provide information for the evaluation of such effects. Methods: By means of a modified staircase procedure the odor (OT) and irritation thresholds (IT) of 15 irritants were determined. These basic chemosensory properties, confining the chemosensory effect range, were investigated in a random sample of 144 persons stratified for gender and age. Those irritants exhibiting high chemosensory potency were selected for the second psychophysical part of the study. Forty-eight persons, again stratified for gender and age, rated the intensity of 13 trigeminal and olfactory perceptions elicited by nine ascending concentrations of the irritants, ranging from the odor to the irritation threshold of the respective substances. Results: Across the investigated chemicals the transition from concentrations eliciting pure olfactory stimulation (OT) to trigeminal stimulation (IT) differed markedly. The carboxylic acids yielded narrow ranges from odor to irritation thresholds, while for the amines (cyclohexylamine, dimethylamine, and trimethylamine) and the esters (ethyl formate and ethyl acetate) these ranges were somewhat wider. The two chemosensory thresholds of ethyl acrylate and ammonia were farthest from each other. Gender and age had only weak impact on the chemosensory thresholds. At present, the results of the intensity ratings could be given for six substances. Among them, the rated pungency for cyclohexylamine, formic acid, and ethyl acetate increased strongest across the nine applied concentrations. Conclusions: By means of these psychophysical approaches a diverse class of chemicals can be described and compared with respect to their chemosensory potency. This information can be used twofold (a) for the evaluation of existing studies reporting sensory irritations and (b) for the design of experimental exposure studies.     

Olfactory sensitivity in medical laboratory workers occupationally exposed to organic solvent mixtures

BACKGROUND: Published epidemiological information relating the effects of occupational exposure to organic solvents (OS) to olfaction is limited. AIMS: The objectives of this pilot study were to measure the chemosensory abilities of medical laboratory employees occupationally exposed to OS mixtures, to compare these with control workers employed within the same occupational setting and to correlate chemosensory performance with OS exposure history and with employees' hedonic (pleasantness) perceptions about workplace OS odors. METHODS: Twenty-four medical laboratory employees (OS-exposed technicians plus control workers minimally exposed to OS) completed a health-related questionnaire, a test of pyridine odor detection threshold, along with a gustatory detection threshold test involving aqueous quinine solutions. Estimates of cumulative hours of OS exposure (CSI) were calculated from self-reports. RESULTS: OS-exposed laboratory technicians detected weaker concentrations of pyridine odor. Positive correlations were detected between CSI estimates to both pyridine detection and the degree that participants reported that OS odors were present in the workplace. However, no association was detected between pyridine detection and how unpleasant workplace OS odors were perceived. The OS-exposed participants were able to detect weaker concentrations of quinine. Compared to controls, OS-exposed workers complained more of experiencing several symptoms while working, including headaches, nasal irritation and mild cognitive impairment. CONCLUSIONS: The results of this cross-sectional pilot study indicated that, compared to controls, medical laboratory technicians exposed to low-level OS mixtures displayed evidence of elevated olfactory sensitivity (hyperosmia) to pyridine odor. The relation of this study's results to chemical intolerance warrants further investigation.     

Biomonitoring of exposure to ethylene oxide and propylene oxide by determination of hemoglobin adducts: correlations between airborne exposure and adduct levels

Objectives: Ethylene oxide (EO) and propylene oxide (PO) are important industrial chemicals. Exposure to these directly acting mutagens may be monitored by determination of their adducts to hemoglobin (Hb). This study establishes correlations between airborne concentrations of EO and PO and their Hb adducts in petrochemical workers. Methods: In three different studies conducted during maintenance shutdown of petrochemical plants the external occupational exposure to EO and PO was assessed by personal air monitoring (PAM). The internal exposure to EO and PO was concomitantly assessed by determination of N-(2-hydroxyethyl)valine (HOEtVal) and N-(3-hydroxypropyl)valine (HOPrVal) in blood samples of the operators using the N-alkyl-Edman degradation method. Results: In the first study, PAM was applied once a month at random over a period of 4 months. Blood samples for Hb-adduct determination were collected at the end of this period. No significant correlation was found between PAM and Hb-adduct data. In the next two studies, PAM was applied to the operators during the entire shift on every working day during the shutdown. Blood samples were collected before and immediately after the shutdown period. Highly significant correlations were found between the increment in the concentration of HOEtVal and HOPrVal over this period and the total exposure to EO and PO, respectively. Conclusions: Time-integrated exposure to EO or PO can be readily and reliably assessed by measurement of the concentration of HOEtVal or HOPrVal in a small blood sample. In workers occupationally exposed to low concentrations of EO or PO, good correlations were found between these Hb adducts and the airborne concentrations of EO and PO. These correlations allow the calculation of tentative biological exposure limits (BELs) for EO and PO. At the current Dutch occupational exposure limit (OEL) for EO (0.84 mg m⁻³, 8-h TWA) the BEL is 3.2 nmol HOEtVal/g globin. At the value of 10 mg m⁻³ (8-h TWA), which is currently being investigated as the new Dutch OEL for PO, the corresponding BEL is 5.3 nmol HOPrVal/g globin. Received: 28 July 1998 / Accepted: 28 November 1998     

Workers’ exposures and potential health risks to air toxics in a petrochemical complex assessed by improved methodology

Objective This study was designed to comprehensively evaluate workers’ potential health risks of exposure to 39 air toxics in the Ta-sher Petrochemical Complex. Methods: Open-Path Fourier Transform Infrared Spectroscopy (OP-FTIR) was used to measure concentrations of air toxics. We used the measured worksite concentrations between 1997 and 1999 at 11 companies in the petrochemical complex, employing 3,100 on-site workers. The 39 measured air toxics included 10 chemicals with acute reference exposure levels (RELa), 19 chemicals with chronic reference exposure levels (RELc), and 3 chemicals classified as Class 1 or 2A human carcinogens by the International Agency for Research on Cancer (IARC). We then used RELa to calculate the hazard index of acute health effects (HI _A ) for workers in individual plants. We also calculated the hazard index of chronic health effects (HIc) and cancer risks for all workers in the entire petrochemical complex. Results: Workers in five companies had HI _A greater than 1 because of toluene, benzene, methyl ethyl ketone, chloroform and isopropanol exposures. Workers in this petrochemical complex had HIc greater than 1 because of acrylonitrile, 1,3-butadiene, hydrogen cyanide, and n,n-dimethylformamide exposures. Risk of hematopoietic system cancer because of benzene and ethylene oxide exposure, and respiratory system cancer because of 1,3-butadiene exposure was estimated to be 3.1–6.1×10⁻⁴ and 5.2–7.1×10⁻⁴, respectively. Conclusions: Our findings indicated that workers in the petrochemical complex might have excess cancer and noncancer risks due to acute or chronic exposures to air toxics from multiple emission sources.     

Ambient monitoring and biomonitoring of workers exposed to N-methyl-2-pyrrolidone in an industrial facility

Objectives: The exposure of seven workers and three on-site study examiners to N-methyl-2-pyrrolidone (NMP) was studied in an adhesive bonding compound and glue production facility. Methods: Airborne NMP was analysed by personal and stationary sampling on activated charcoal tubes. NMP and its main metabolites, 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI), were analysed in pre-shift and post-shift spot urine samples by gas chromatography-mass spectrometry. The workers were examined with respect to irritation of the eyes, the mucous membranes and the skin, and health complaints before and after the work-shift were recorded. Results: The time-weighted average concentration of NMP in most work areas varied between 0.2 and 3.0 mg/m³. During the manual cleaning of stirring vessels, valves and tools, 8-h TWA exposures of up to 15.5 mg/m³ and single peak exposures of up to 85 mg/m³ were observed. NMP and its metabolites were detected in two pre-shift urine specimens. NMP and 5-HNMP concentrations in post-shift urine samples of five workers and three on-site study examiners were below 125 μg/g creatinine and 15 mg/g creatinine, respectively, while two vessel-cleaning workers showed significantly higher urinary NMP concentrations of 472 and 711 μg/g creatinine and 5-HNMP concentrations of 33.5 and 124 mg/g creatinine. 2-HMSI was detectable in four post-shift samples (range: 1.6–14.7 mg/g creatinine). The vessel cleaner with the highest NMP exposure reported irritation of the eyes, the upper respiratory tract and headaches. Conclusions: The results of this study indicate a relatively low overall exposure to NMP in the facility. An increased uptake of NMP occurred only during extensive manual vessel cleaning. Health complaints associated with NMP exposure were recorded in one case and might be related to an excessive dermal exposure due to infrequent and inadequate use of personal protective equipment.     

Occupational exposure to low concentrations of carbon disulfide as a risk factor for hypercholesterolaemia

Objective: The objective of this study was to investigate the effect of occupational exposure to carbon disulfide (CS₂) concentrations below threshold limit value (TLV)-time-weighted average (TWA) (31 mg/m³) on total cholesterol, blood pressure and the prevalence of coronary heart disease (CHD). Methods: A cross-sectional study involving 141 viscose rayon workers (64 men), and 141 age- and gender-matched controls without occupational contact with noxious chemicals, was carried out. The probability for CHD was determined by means of the WHO questionnaire and was 12-lead electrocardiography-coded using Minnesota criteria. Blood pressure was measured by the standardized method of the WHO and blood was examined for total cholesterol. A cumulative exposure index (CS₂ index) was calculated for each worker by multiplying the number of years held in a particular job, by the CS₂ concentrations in that job-environment. According to the CS₂ index, the exposed workers were distributed into two groups: group 1 (CS₂ index <100) and group 2 (CS₂ index ≥100). Results: Depending on the job and specific work place the CS₂ concentrations were between 1 and 30 mg/m³. Cholesterol levels were significantly higher in the exposed group (4.9 ± 0.7) compared with the controls (4.6 ± 0.7). Adjustment for age, smoking, body-mass index (BMI) and gender showed the significant effect of the CS₂ index on the total cholesterol (P < 0.001). The prevalence of hypercholesterolaemia was significantly higher in the exposed group (42.6%), compared with the controls (26.2%); odds ratio (OR) (adjusted for potential confounders) was 2.56, 95% CI 1.47–4.46. Logistic regression showed a significantly increased risk for elevated cholesterol in group 2 (OR 5.52; 95% CI 2.81–10.83). No significant effect of CS₂ index on blood pressure and CHD prevalence was found. Conclusions: The results of our study show that occupational exposure to CS₂ concentrations below 31 mg/m³ and a CS₂ index >100 may increase total cholesterol. Our results imply that even the CS₂ concentrations below TLV-TWA may produce morbid changes, and suggest the mechanism of the effect of CS₂, leading to lipid metabolism disturbances and acceleration of atherosclerosis. Received: 1 February 2000 / Accepted: 24 June 2000     

Perceived odor and irritation of isopropanol: a comparison between naïve controls and occupationally exposed workers

OBJECTIVES: To assess sensory irritation levels from isopropanol (IPA) unconfounded by subjective evaluations of odor for comparison against the recommended exposure limits (400 ppm threshold limit value (TLV); American Conference of Governmental Industrial Hygienists). METHOD: The lateralization method was used to assess intra-nasal irritation thresholds for IPA, while odor detection thresholds were also measured. Thresholds for 1-butanol and phenyl ethyl alcohol (PEA) were obtained as positive and negative irritant controls. To compare potency and hedonic characteristics, subjects provided subjective ratings of odor, irritation and annoyance intensity for three concentrations of each chemical. Workers occupationally exposed to IPA ( n=26) were compared with previously unexposed controls ( n=26). RESULTS: The (geometric) mean odor detection threshold for IPA was slightly higher among exposed workers than controls (39 ppm vs. 11 ppm). Lateralization thresholds measuring intra-nasal irritation were elevated when compared with controls (6,083 ppm in exposed workers vs. 3,361 ppm in na?ve controls), with a significantly higher proportion of phlebotomists being unable to lateralize the maximum concentration regarded as safe, than controls. Calculations of the 6th percentile for lateralization thresholds revealed that 95% of the sample did not experience sensory irritation below 512 ppm. Thus, while odor detection thresholds were well below the current recommended exposure limits, the irritation thresholds were well above these values. The odor, irritation and annoyance from IPA was perceived, on average, as between weak and almost strong, from lowest to highest concentration. CONCLUSIONS: The results indicate that current exposure guidelines would be adequately protective of the acute adverse effect of nasal sensory irritation, as operationally defined by the intra-nasal lateralization threshold. Exposures to higher concentrations should perhaps be evaluated on the basis of existing knowledge about systemic, rather than local (e.g., irritation), toxic effects. IPA appears to be a weak sensory irritant and occupational exposure to IPA appears to elicit small changes in sensitivity that do not generalize to other odorants (e.g., PEA and 1-butanol) and are likely to be reversible.     

Neurotoxicity of long-term low-level exposure to carbon disulphide: results of questionnaire, clinical neurological examination and neuropsychological testing

 Objective. Carbon disulphide (CS₂) is highly neurotoxic. There is ample evidence of damage to the peripheral and central nervous system. The air concentration at which such adverse effects can first be observed is presently a subject of controversy. Methods. In a cross-sectional study of CS₂-exposed workers from the viscose industry and healthy controls, data on neurological complaints, basic laboratory diagnosis, clinical neurological examination and neuropsychological testing were evaluated. Data were from 222 workers in the viscose industry exposed to CS₂ and 191 employees from the same factory with similar physical and psychological stress factors but without occupational contact with neurotoxic substances. Multiple linear or multiple logistic regression analysis was used to check for statistical differences. Results. The median of the CS₂-measurements using personal air sampling was below the current maximum concentration permissible (MAK value) in Germany (10 ppm) in all departments. The threshold limit value was, however, exceeded in almost 10% of the persons investigated. Exposure fluctuated between <0.2 and 65.7 ppm (median of all departments was 4.02 ppm). As a parameter of internal exposure, CS₂-metabolite 2-thio1,3-thiazolidine-4-carboxylic acid (TTCA) concentrations in the urine of the exposed persons were between <0.16 and 10.9 mg/g creatinine (median 1.43 mg/g). Conclusions. Neither an increase in subjective complaints nor an increase in pathological findings in clinical-neurological and neuropsychological examination could be found in persons exposed to CS₂ at the exposure levels described. Received: 19 December 1995/Accepted: 18 July 1996     

Olfactory toxicity: long-term effects of occupational exposures

Objective: To present and discuss the results of research on olfactory function impairments related to chronic occupational exposure to industrial chemicals. Methods: This review is mainly focused on the results of epidemiological studies on olfactory function, evaluated using quantitative testing methods, in workers chronically exposed to airborne industrial chemicals. Papers published in peer-reviewed scientific journals were mainly considered. Results: The prevalence of olfactory impairments related to occupational exposure to chemicals is unknown: frequencies ranging 0.5–5% of all olfactory dysfunctions have been proposed, considering both exposure to chemicals and the use of pharmaceutical drugs, but the real relevance of this problem is possibly overlooked, especially considering that occupational exposure may account for a significant part of “idiopathic” smell disorders, i.e., the 10–25% of all olfactory problems within the general population. An adverse effect has been reported in workers chronically exposed to some metals as cadmium, chromium, manganese, arsenic, mercury, and organic lead, and to other chemicals as acrylates, styrene, and solvent mixtures. The results of relevant studies are discussed. A problem in the evaluation of data is that different methods have been applied in different studies, affecting the comparability of results. Conclusions: To date, knowledge of the effect of chronic occupational exposure to industrial chemicals on olfactory function is largely incomplete, but supports the hypothesis that olfactory neuroepithelium is susceptible to environmental exposures to chemicals. Occupational-related olfactory impairment is usually sub-clinical, and can be only detected using adequate quantitative olfactory function testing procedures. Available data show the need for further good quality research in this field.     

Olfactory function in workers exposed to styrene in the reinforced-plastics industry

BACKGROUND: Impairment of olfactory function in humans has been associated with occupational exposure to volatile chemicals. To investigate whether exposure to styrene was associated with olfactory impairment, olfactory function was examined in workers with a minimum of 4 years exposure to styrene in the reinforced-plastics industry (current mean exposure: 26 ppm, range: 10-60 ppm; historic mean dose: 156 ppm-years, range: 13.8-328 ppm-years) and in a group of age- and gender-matched, unexposed controls. METHODS: Olfactory function was assessed using a standardized battery that included tests of threshold sensitivity for phenylethyl alcohol (PEA), odor identification ability, and retronasal odor perception. Odor detection thresholds for styrene were also obtained as a measure of specific adaptation to the work environment. RESULTS: No differences were observed between exposed workers and controls on tests of olfactory function. Elevation of styrene odor detection thresholds among exposed workers indicated exposure-induced adaptation. CONCLUSIONS: The present study found no evidence among a cross-section of reinforced-plastics industry workers that current or historical exposure to styrene was associated with impairment of olfactory function. Taken together with anatomical differences between rodent and human airways and the lack of evidence for styrene metabolism in human nasal tissue, the results strongly suggest that at these concentrations, styrene is not an olfactory toxicant in humans.     

Divergent Kinetics of hsp70 Induction in Oniscus asellus (Isopoda) in Response to Four Environmentally Relevant Organic Chemicals (B[a]P, PCB52, γ-HCH, PCP): Suitability and Limits of a Biomarker

Mature specimens of the isopod Oniscus asellus were maintained on soil and leaf litter to which was added different concentrations of either benzo[a]pyren (B[a]P), 2,2′,5,5′-tetrachlorobiphenyl (PCB52), γ-hexachlorocyclohexane (γ-HCH), or pentachlorophenol (PCP) for a maximum of 14 days. Time-dependent investigation of the body level of the 70 kD stress protein group (hsp70) in the isopods revealed a significant but transient induction of the hsp70 response after about 24 h of exposure to PCB52 or B[a]P. Despite continuous exposure, the hsp70 level decreased subsequently and ended up close to or below the control level independent of the concentration of PCB52 or B[a]P in the substrate. All applied PCP or γ-HCH concentrations also resulted in an initial peak of hsp70 response after 24 h of exposure and a second peak after several days of exposure, as well as an elevated hsp70 level throughout the period of exposure. Although acute stress conditions posed by all four organic chemicals were monitored by stress protein induction, hsp70 can act as a biomarker of chronic exposure and effect for PCP and γ-HCH only. Received: 9 April 1998/Accepted: 16 August 1998     

Urinary N -acetyl-β-glucosaminidase as an indicator of renal dysfunction in electroplating workers

Objectives: To investigate chromium-induced renal dysfunction in electroplating workers. Methods: A cross-sectional study was used to evaluate four biochemical markers of renal function. A total of 178 workers were divided into 3 comparable groups consisting of 34 hard-chrome plating workers, 98 nickel-chrome electroplating workers, and 46 aluminum anode-oxidation workers, who represented the reference group. Ambient and biological monitoring of urinary chromium were performed to measure exposure concentrations. Results: Overall, urinary chromium concentrations were highest among hard-chrome plating workers (geometric mean 2.44 μg/g creatinine), followed by nickel-chrome electroplating workers (0.31 μg/g creatinine) and aluminum workers (0.09 μg/g creatinine). Airborne chromium concentrations were also highest in the hard-chrome plating area (geometric mean 4.20 μg/m³), followed by the nickel-chrome electroplating area (0.58 μg/m³) and the aluminum area (0.43 μg/m³). A positive correlation was found between urinary chromium and airborne concentrations (r = 0.54, P < 0.01). Urinary concentrations of N-acetyl-β-d-glucosaminidase (NAG) were also highest among hard-chrome plating workers (geometric mean 4.9 IU/g creatinine), followed by nickel-chrome workers (3.4 IU/g creatinine) and aluminum workers (2.9 IU/g creatinine). The prevalence of “elevated” NAG (>7 IU/g creatinine) was significantly highest among hard-chrome plating workers (23.5%), then among nickel-chrome workers (7.1%) and aluminum workers (8.7%). Differences in β₂-microglobulin, total protein, and microalbumin were not significant. Conclusion: The author's evidence indicates that NAG is an early indicator of renal dysfunction in hard-chrome plating workers.     

Blood benzene concentrations in workers exposed to oxygenated fuel in Fairbanks,Alaska

 Objective: In November 1992 residents of Fairbanks, Alaska became concerned about the potential health effects of an oxygenated fuel program during which 15% (by volume) methyl tertiary butyl ether (MTBE) was added to gasoline. To address those concerns, we earlier completed a survey of occupational exposure to MTBE. We conducted a follow-up survey of workers’ exposure to benzene from gasoline in Fairbanks. Design: Cross-sectional exposure survey. Methods: We examined blood concentrations of benzene from a convenience sample of workers taken in December 1992 during the oxygenated fuel program and from another convenience sample of workers taken in February 1993 after the program was suspended. Results: In December, the median blood benzene concentration of samples taken from four mechanics after their workshift (postshift) was 1.32  μg/l (range, 0.84–2.61 μg/l), and seven nonmechanics (drivers and other garage workers) had a median postshift blood benzene concentration of 0.27 μg/l (range, 0.09– 0.45 μg/l). In February, nine mechanics had a median postshift blood benzene concentration of 1.99 μg/l (range, 0.92–3.23 μg/l), and nine nonmechanics had a median postshift blood benzene concentration of 0.26 μg/l (range, 0.2–0.46 μg/l). Conclusion: Mechanics had higher blood benzene concentrations than did nonmechanics, but further study is needed to determine the impact of the oxygenated fuel program on exposure to benzene. Received: 6 November 1995/Accepted: 2 April 1996     

Allylmercapturic acid as urinary biomarker of human exposure to allyl chloride.

OBJECTIVE: To evaluate the use of urinary mercapturic acids as a biomarker of human exposure to allyl chloride (3-chloropropene) (AC). During three regular shut down periods in a production factory for AC, both types of variables were measured in 136 workers involved in maintenance operations. METHODS: Potential airborne exposure to AC was measured by personal air monitoring in the breathing zone. In total 205 workshifts were evaluated. During 99 workshifts no respiratory protection equipment was used. Mercapturic acid metabolites were measured in urinary extracts by gas chromatography-mass spectrometry (GC-MS). RESULTS: During 86 work shifts when no respiratory protection was used the air concentrations of AC were below the Dutch eight hour time weighted average (8 h-TWA) occupational exposure limit (OEL) of AC (3 mg/m3), whereas in 13 workshifts the potential exposure, as measured by personal air monitoring, exceeded the OEL (3.3 to 17 mg/m3). With the aid of GC-MS, 3-hydroxypropylmercapturic acid (HPMA) was identified as a minor and allylmercapturic acid (ALMA) as a major metabolite of AC in urine samples from the maintenance workers exposed to AC. The concentrations of ALMA excreted were in a range from < 25 micrograms/l (detection limit) to 3550 micrograms/l. The increases in urinary ALMA concentrations during the workshifts correlated well with the 8h-TWA air concentrations of AC (r = 0.816, P = 0.0001, n = 39). Based on this correlation, for AC a biological exposure index (BEI) of 352 micrograms ALMA/g creatinine during an eight hour workshift is proposed. In some urine samples unexpectedly high concentrations of ALMA were found. Some of these could definitely be attributed to dermal exposure to AC. In other cases garlic consumption was identified as a confounding factor. CONCLUSION: The mercapturic acid ALMA was identified in urine of workers occupationally exposed to airborne AC and the increase in ALMA concentrations in urine during a workshift correlated well with the 8 h-TWA exposure to AC. Garlic consumption, but not smoking, is a potential confounding factor for this biomarker of human exposure to AC.     

Urinary cobalt as a measure of exposure in the wet sharpening of hard metal and stellite blades

 The measurement of urinary cobalt as an estimator of exposure to airborne cobalt was evaluated during the wet sharpening of hard metal and stellite blades. The following possible confounding factors were also studied: smoking habits, personal hygiene, cobalt absorption through the skin, beer drinking, and vitamin B₁₂ consumption. The study was conducted in 16 different workplaces manufacturing or maintaining blades and in laboratory experiments. Cobalt contamination and its removal from workers’ hands were studied with different hand-washing methods, and cobalt from used gloves was also analyzed. The Finnish biomonitoring action level of 600 nmol/l (35.4 μg/l) was exceeded in 4 of the 16 workplaces, and the mean concentration of urinary cobalt was 241 (8–2705) nmol/l [14.2 (0.5–160)  μg/l]. The coefficient of correlation between the cobalt concentrations in the air and in the workers’ urine was 0.753. The urinary cobalt concentration corresponding to the Finnish occupational exposure limit for airborne cobalt (0.05 mg/m³) was 686 nmol/l (40.5 μg/l). The level of personal hygiene affected the urinary cobalt concentrations, and cobalt was absorbed through the skin. Beer and vitamin B₁₂ consumption did not have any effect on the urinary levels of cobalt. The workers who smoked had higher urinary concentrations of cobalt than the nonsmoking workers. High concentrations of cobalt in coolants contaminated the workers’ skin, and hand-washing did not remove cobalt very effectively. The results indicate that urinary cobalt can be used reliably to assess workers’ exposure to airborne cobalt when wet-tip grinding processes are used. The results also show that workers’ exposure to cobalt can be reduced by improving skin protection and personal hygiene in workplaces. Received: 29 January 1996 / Accepted: 2 May 1996     

Odor thresholds and irritation levels of several chemical substances: a review

A collation of odor threshold data for approximately 450 chemical substances is presented. The range of odor thresholds reported in the literature is shown along with any reported threshold of irritation to humans. These data can assist the industrial hygienist in determining when an "odor" may be in excess of the Threshold Limit Value, when an organic vapor respirator is not acceptable due to the lack of an odor warning at the end of a cartridge life, and where odors may not indicate a hazard due to extremely low odor thresholds which may be well below the respective TLVs.