Search

trans, trans-Muconic acid (MA), a urinary ring-opened metabolite of benzene, is a newly proposed biological indicator of benzene exposurewhich should enable the assessment of low levels of exposure to thisubiquitous environmental pollutant. The presence of MA in the urine of non-occupationally exposed people is generally attributed to world-wide contamination of the environment by benzene (arising from such sources as smoking and other combustion, urban pollution from vehicles and maybe by food contamination). But, examination of the scientific literature reveals that a common food preservative and fungistatic agent, sorbic acid (SA), is also converted into MA, although in traceamounts. The permitted maximum concentration of SA in food ranges from 0.2 to 2 g.kg-1 and the acceptable daily intake (ADI-FAO/WHO) is 25 mg.kg-1 of body weight. The question, therefore, is whether the amount of MA excreted as a metabolite of SA can make a significant contribution to the total MA excreted. If so, the specificity of MA as a biological indicator for benzene exposure assessment is in doubt. Four experiments in 2 subjects were set up to try to clarify the effect on the urinary excretion of MA of the experimental ingestion of SA (2 doses of 447 and 44.7 mg); urine samples were collected, in fractions as voided, for 24 h before and 48 (or 60 h) after SA ingestion. The total amounts of MA excreted during the 24 h before ingestion of SA were respectively 79 and 34 mg in the 2 subjects; after ingestion of 447 or 44.7 mg of SA the total excretion of MA was at least respectively 20 and 2 times the background levels (when the single dose of SA was ingested) and at least 10 and 3 times (when the SA was given in divided doses). The elimination of MA after ingestion of SA was complete in 24 h; the peak concentrations always appeared in the first urine sample after the ingestion of the substance and they were more than 90 times and more than 3 times the basal levelsres [ABSTRACT FROM AUTHOR]

S-Phenylmercapturic acid (PMA), a urinary metabolite which derives from the conjugation of benzene epoxide with glutathione, has been recently included in the list of the biological markers of benzene exposure. We have evaluated the urinary PMA levels in 145 workers exposed to benzene and in 87 subjects not occupationally exposed to the solvent (45 smokers and 42 non-smokers). In non-exposed persons, the background PMA excretion was nearly constant during one day (urine samples were collected in the morning, afternoon, and evening) and in smokers the mean PMA levels were higher than in non-smokers (9.6 vs 1.3 micrograms/g creatinine). This difference was presumably due to the extra-exposure to benzene (from cigarette smoke) in smokers compared with non-smokers, in fact a close relationship was found between PMA excretion and urinary benzene concentration (r = 0.86). Urine samples from workers exposed to benzene (airborne mean concentration = 0.52 ppm) showed higher mean levels of PMA (37.6 micrograms/g creatinine) than samples taken from not occupationally exposed subjects, both smokers and non-smokers. The mean biotransformation rate of benzene to PMA was 0.073%, with a large inter-individual variability (range = 0.002-0.21%). Also, statistical analysis of data revealed a clear bimodal distribution pattern of the conversion rate frequencies in the population examined: this is consistent with the hypothesis of the presence of "slow" and "fast" converters, due to the polymorphism of glutathione-S-transferase isozymes.

In the first part of this report the theory of the heat exchange between human body and external environment is developed. In particular, the problems concerning energy expenditure and heat production [metabolic heat] during physical activity, the heat exchange between internal organs and body surface, and its elimination are considered. Proposal of heat exchange equations (in case of conduction, convection, evaporation, radiation transport) are made, and the involved parameters and constants are indicated. Some pages are devoted to heat exchange through the lung and to "perspiratio insensibilis". In the second part the problems concerning the wellbeing and the thermal discomfort are discussed. A description of some widely employed indices of thermal stress, strain and comfort concludes the report [P4SR index, HSI index, ITS index, TTL index, HR index, WBGT index, TE indices]. In the end, the Fanger equations of thermal comfort are presented and discussed.

Background: The specificity of trans,trans-muconic acid (MA) as a biomarker of exposure to low benzene levels and the role of sorbic acid (SA) as a confounding factor were evaluated. MA, a urinary ring-opened metabolite of benzene, has been recently proposed for the biological monitoring of populations exposed to low levels of this chemical. The usual presence of MA in urine of non-occupationally exposed people is generally attributed to benzene world-wide contamination (mainly by smoking habits, urban pollution, and maybe by food contamination). However, the scientific literature reveals that the common food preservative and fungistatic agent SA is converted into MA though in trace amounts., Methods: Urinary benzene and MA before and after administration of SA were measured in smokers and non-smokers. Benzene dissolved in urine was analyzed injecting a headspace sample in a gas-chromatografic system. Urinary MA was measured by means of a HPLC apparatus., Results: The mean background values of MA were about 60 mg/L (or 50 mg/g creat.); after experimental administration of SA (447 mg), the mean urinary MA concentration became more than 20 times higher. The biotransformation rates of SA into MA after ingestion of 447 mg of SA ranged from 0.05 to 0.51%. The ratio between unmetabolized benzene in the two groups of smokers and non-smokers was significantly different from the ratio between MA in the same two groups., Discussion: Other sources of MA excretion, different from benzene, influence the urinary concentration of the metabolite: only 25% of MA background values can be attributed to benzene. The urinary MA induced by 100 mg of ingested MA is 77% of that expected after an 8-hour benzene exposure to 0.5 ppm (current threshold limit value according to ACGIH). In conclusion, MA is not a sufficiently specific biomarker of low benzene exposure; a significant effect of SA ingestion is predictable.

The biological monitoring of inhalation anaesthetics. Occupational exposure to inhalation anaesthetics is an undesired consequence of the work in the operating theatre. Anaesthesia is currently practised using nitrous oxide associated with one or more potent anaesthetics (halothane, enflurane, isoflurane). In the present study we evaluated the occupational exposure to inhalation anaesthetics during anaesthesia in 190 operating theatres of 41 hospitals in Italy. Nitrous oxide, halothane, enflurane, isoflurane were detected in the urine of 1521 exposed subjects (anaesthetists, surgeons and nurses). Significant correlations were found between the anaesthetic concentrations in urine produced during the shift (Cu) and anaesthetic environmental concentrations (CI). The results show that the urinary anaesthetic concentration can be used as an appropriate biological exposure index. The biological threshold values (urinary concentration values) proposed are the following: nitrous oxide, 15, 28 and 57 micrograms/L for an environmental exposure of 25, 50 and 100 ppm respectively; halothane, 97 micrograms/L (for an environmental exposure of 50 ppm), 6.1 micrograms/L (for an environmental exposure of 2 ppm) and 3.3 micrograms/L (for an environmental exposure of 0.5 ppm); enflurane, 145 micrograms/L (for an environmental exposure of 50 ppm), 22.7 micrograms/L (for an environmental exposure of 10 ppm), 3.7 micrograms/L (for an environmental exposure of 1 ppm); isoflurane, 5.3 micrograms/L (for an environmental exposure of 2 ppm) and 1.8 micrograms/L (for an environmental exposure of 0.5 ppm). These values apply to urine samples collected at the end of 4-hours' exposure to the anaesthetics.

The knowledge of the partition coefficients between the air and arterial blood and between the blood and the different physiological compartments of the body are essential to the mathematical modelling of the respiratory uptake and elimination of toxic vapours. Partition coefficients of methyl tertbutyl ether (MTBE) in saline, olive oil, urine and human blood, and various rat tissues were calculated after gas-chromatographic quantification of MTBE in the air phase. The blood/air, urine/air saline/air, fat/air and oil/air partition coefficients (lambda) are respectively: 20.0, 15.6, 15.3, 142.0 and 138.

The aim of this study was to determine if a relationship existed between some inhalation anesthetics airborne exposure levels (Cl) and the concentration of anesthetics in samples of urine produced throughout the exposure time (Cu). The concentrations of nitrous oxide (N2O), halothane (fluothane), enflurane (ethrane), and isoflurane (forane) in the ambient atmosphere were determined in 190 operating theaters of 41 hospitals in Italy. Nitrous oxide, halothane, enflurane and isoflurane were detected in the urine of 1521 exposed subjects (anesthetists, surgeons, and nurses). The environmental measurements were performed using personal passive samplers, and the biological measurements were performed using the head space method. Significant correlations were found between the anesthetics concentration in urine produced during the shift collected after a 4-h exposure (Cu, microgram/L) and anesthetics environmental concentration (Cl, ppm). The results show that the urinary anesthetic concentration can be used as an appropriate biological exposure index. The biological values (urinary concentration values) proposed are the following: nitrous oxide, 25 micrograms/L, for an environmental value of 50 ppm; halothane, 97 micrograms/L, corresponding to 50 ppm of environmental exposure; 6.2 micrograms/L, corresponding to 2 ppm of environmental exposure; enflurane, 145 micrograms/L for an environmental exposure of 75 ppm and 5.6 micrograms/L for an environmental exposure of 2 ppm; isoflurane, 5.3 micrograms/L for an environmental exposure of 2 ppm. The values proposed are the respectively 95% lower confidence limit and therefore should be considered as a protection for the individual, especially if each biological value is corrected according to analytical variability of the measurements. In our opinion, the method of choice in the assessment of occupational exposure to inhalation anesthetics is the measurement of the urinary anesthetic concentration.

Biological monitoring of occupational exposure to enflurane (ethrane) can be achieved by measuring concentrations of inorganic fluorides in the blood and urine and of enflurane in alveolar air and venous blood. Measurement of these concentrations, however, has limitations. Another method for monitoring exposure to enflurane is to measure its concentration in urine throughout the period of exposure. In this study, we measured the environmental and urinary concentrations of enflurane. Enflurane in the ambient atmosphere was determined in 18 operating theaters of eight hospitals in Italy. Ambient air concentrations exceeded the National Institute for Occupational Safety and Health-recommended time-weighted average exposure level of 1 ppm (median: 1.31 ppm). Enflurane was detected in urine of 159 exposed subjects (anesthetists, surgeons, and nurses). A significant correlation was found between enflurane concentration in urine produced during the shift and environmental concentration (r = 0.77, p = .0001). The results showed that urinary enflurane concentration can be used as an appropriate biological exposure index. The biological values proposed are 153 micrograms/l, corresponding to 75 ppm of environmental exposure; 22 micrograms/l, corresponding to 10 ppm of environmental exposure; and 3.5 micrograms/l, corresponding to 1 ppm of environmental exposure. The proposed values can be regarded as time-weighted average samples, reflecting exposure for a 4-h period.

Workplace pollutants, inhaled by exposed people, can be subsequently excreted by the kidney as biotransformed or by the lung as parent substances. In both cases the concentration values need to be corrected to a given hydration level (the urinary metabolites) or to a value adjusting the effects of respiratory manoeuvres and those of the mixing between alveolar and dead space air (the volatile substances eliminated through the respiratory tract). The classical methods of standardization of urinary values lie in expressing the data as a value adjusted to a constant specific gravity of urine (1.020) or as a creatinine-adjusted concentration (amount of a compound in urine per gram of urinary creatinine). In the light of the recent researches, such adjustment would not be sufficient to correct the effects of the variability due to urinary volume or flow rate. New formulas to standardize the crude values of urinary concentration have been proposed; such adjustment should be more suitable. The concentration of volatile compounds present in expiratory air samples can be modified by hyperventilation or hypoventilation during sampling manoeuvres (1st factor) and by the mixing between dead space and alveolar air (2nd factor). These two factors similarly affect the CO2 concentration or CO2 partial pressure. Then, a proper standardization of the concentration of the pollutants in expired air samples might be their adjustment to a value corresponding to the normal level of alveolar CO2 partial pressure (PACO2 = 40 mmHg) or alveolar CO2 concentration (FACO2 approximately 0.055 or 5.5%).

The authors report the parameters which rule the absorption and elimination of polluting solvent vapours in exposed subjects (ventilation, pulmonary capillary flow, solubility coefficients, environmental concentration, exposure times). These parameters are included in the equations showing the absorption and elimination indexes and lung clearances. The absorption and elimination indexes implied are discussed stressing their practical usefulness in the field of biological monitoring, industrial hygiene and in preventive medicine.

A simple method for assessing the physical working capacity [in terms of maximal work capacity, loss of work capacity in diseased people, long-term work capacity (or critical power), endurance time] is proposed. The method consists in performing two "6 minutes workload" of different but known power and in measuring the corresponding heart rates and O2 uptakes at steady state. The effort was a "step-test" at different height of the step and rate of ascent and descent from it. The O2 uptake was measured either directly or indirectly from a nomogram (starting from the step height and the frequency of the up and down). The measured and estimated values of O2- uptake were very well correlated and this might be an indication for the method to be used in not equipped factory ambulatory or directly in workplaces. The maximal capacity to perform an effort was calculated on the basis of the linear regression between heart rate and O2-uptake, calculating the O2 maximal values (VO2MAX) from the predicted maximal heart rate (FMAX); analogously, the critical power was obtained by calculating the O2 critical values (VO2CRIT) from the predicted critical heart rate (FCRIT); the loss of work capacity is the difference between two maximal powers, the theoretical and the measured one. The endurance time was measured on the basis of the hypothesis of a linear regression between level of an effort and logarithm of the time to perform it. Finally, a few procedures to assess the actual work capacity in subjects with pulmonary or blood diseases are discussed; in these subjects the O2 transfer might be limited by ventilation disorders or by low content of haemoglobin.

Data on long-term biological monitoring in two groups of workers engaged in cleaning operations in a wool factory and exposed to methylchloroform are presented. The longitudinal survey lasted one year and brought about 19 random systematic sampling (once or twice a month for everyone of the 13 subjects monitored). The biological marker adopted was the urinary concentration of the solvent as such, according to a previously studied method. The collected data allowed to measure: the annual average level of exposure (estimated by the long term geometric mean); the day to day variation of the true daily exposure averages (estimated by the geometric standard deviation); the probability of overexposure (daily exposures exceeding the biological exposure limit) and the yearly number of work shifts of overexposure. The usefulness of performing long-term surveys of occupational exposure to the chemical substances by mean of longitudinal biological monitoring is discussed.

Benzene is a widely diffuse solvent (atmosphere, cigarette smoke, some foods); in the industrial environment benzene is currently present at concentrations of ppm. A valid method of biological monitoring that is easy to perform is needed for assessing occupational and non-occupational exposures. A new method has been developed to evaluate low concentrations of benzene in urine samples by means of a "dynamic" headspace (50 ml of urine in a 120 ml vial). The urine is saturated with anhydrous Na2SO4 in order to support the entrance of benzene in the air over the urine. The solvent is stripped from the urine surface and concentrated on an adsorbent substrate (Carbotrap 100 tube) by means of a suction pump (150 ml/min). A simultaneous intake of filtered air through a charcoal tube allows wash-up of the headspace. Benzene is thermically desorbed and injected in a column (Thermal tube desorber-Supelco; 370 degrees C thermal flash; borosilicate capillary glass column SPB-1 60 m length, 0.75 mm I.D., 1 micron film thickness; G.C. Dani 8580-FID). The detection limit of the method is about 50 ng/l and the variation coefficient is 4.7%. The method was checked on urine samples of 5 non-smokers and 5 smokers: mean values of 135 and 944 ng/l respectively were obtained. A further analysis on urine samples of 60 smokers revealed a significant relationship (p less than 0.001) between urinary benzene concentrations and C0 alveolar concentrations (r = 0.626). A close relationship between benzene exposure levels and urinary concentrations was found in a group of workers exposed to low environmental benzene concentrations (mean value 1200 micrograms/m3) (r = 0.763).

The AA describe the realise of an open circuit exposure chamber: it enables to reach solvent concentration levels that are continuously monitored and kept within the limits of acceptability. The room can be employed in studies and experimental researches on the respiratory absorption levels of airborne pollutants in man. The following data are reported: on microclimatic parameters, on the monitoring of CO2 concentration in the room when someone is inside, on the solvent concentration measures in different points of the room, on the monitoring of the quickness to reach the steady-state and wash-out in the room, on the available concentration ranges.

The aim of this paper was to evaluate the lambda values of this group of solvents experimentally, by means of an analytical method which has already been used for other solvents. During our experiments we found that most acetates we tested (n-butyl-acetate; sec.butyl-acetate; ter-butyl-acetate; ethyl-acetate; amyl-acetate; methyl-acetate; n-propyl-acetate) were particularly unstable and hydrolyzed rapidly in alcohol and in the corresponding acid. The "in vitro" behaviour of these substances allow to draw the following conclusions: 1) For the acetates it is not possible to measure the values since the involved substances are chemically unstable in blood. 2) As it was shown by the half-life times of the "in vitro" acetates, the alcohols and the corresponding acids, are released rapidly in blood. 3) The biological monitoring of the acetates in expired air is not very significant; perhaps it is better to measure the corresponding alcohol in expired air. 4) In some cases the TLV of the alcohols is much lower than for the corresponding acetates; this finding and the rapid biotransformation we observed make us think that the TLV's proposed for some acetates are too high.

The results are reported of a retrospective study carried out by the authors on 717 workers of a chemical industry whose exposure was diversified and quantified through a work environment survey. A comparison between "risk indicators" and both objective (respiratory function changes) and subjective (chronic bronchopneumopathy symptoms) "risks" showed a significant probability of the causal role played by work environment pollution in respect of the repiratory changes found by the authors.

N-hexane and toluene in the urine of occupationally exposed subjects. Measurement and significance of their presence. The determination of n-hexane and toluene in urine was performed in 23 subjects who were occupationally exposed to n-hexane and in 8 subjects exposed to toluene, by means of the head space technique. A Hewlett-Packard 5880 A gas chromatograph supplied with Hewlett-Packard 5970 A Mass Selective Detector was employed. The Authors found significant correlations between urine concentration of the substance and environmental concentration (for n-hexane r = 0,866; for toluene r = 0,770.

Fifteen volunteers were exposed to an acetone vapor concentration of 964-8, 610 mumol/m3 (56-500 mg/m3) for 2-4 h in an exposure chamber. Ten subjects were at rest during the exposure, and five were exposed at alternate rest and light physical exercise. Subsequently 104 workers occupationally exposed to acetone were studied. The relative uptake averaged about 53%, and the ratio of the alveolar concentration to the environmental concentration averaged about 0.28. Both for the experimentally exposed subjects and the occupationally exposed workers the urinary acetone concentration showed a linear relationship to the corresponding environmental time-weighted average concentration. A linear equation also existed between urinary concentrations and the amounts of acetone absorbed. The findings enable a consideration of the urinary concentration of the unaltered acetone as an appropriate exposure indicator and the proposal of a "biological equivalent threshold" to be used in the field of biological monitoring.

The Authors describe some methods (at constant pressure and constant volume) which can be used when solubility coefficients of gas and vapours in liquids (water, blood, oil etc.) are to be measured; they are easily performed methods, which are based on the validity of Henry's law.

Twenty human volunteers were exposed to styrene vapor at 273-1 654 mumol/m3 (28.4-172.3 mg/m3) for a period of 1 to 3 h at rest (15 cases) and during light physical exercise (5 cases). Subsequently 51 workers occupationally exposed to styrene were studied during a workweek (median value 1 138 mumol/m3, geometric standard deviation 2.23). As expected, the relative uptake averaged about 65%, and the ratio of the alveolar concentration to the time-weighted average of the environmental concentration averaged about 0.15. Both in the experimentally exposed subjects and in the occupationally exposed workers the urinary styrene concentration showed a linear relationship to the corresponding environmental time-weighted average concentration. The correlation coefficients of the regression lines ranged between 0.88 (occupationally exposed group) and more than 0.93 (experimentally exposed groups). The regression coefficients were closely linked to the amount of styrene taken up and to the exposure times. The findings show that the urinary styrene concentration can be used as an appropriate biological exposure indicator whose meaning differs from that of other suggested indices. As an example, in occupationally exposed subjects performing moderate work the urinary styrene concentration corresponding to the time-weighted average of the threshold limit value is 815 nmol/l, and the 95% lower confidence limit (biological threshold) is 740 nmol/l.

Organic solvents are generally volatile substances that are absorbed mainly through the lungs; they are eliminated chiefly through the lungs and kidneys. In urine they are present as metabolites and, in very little part, as parent compound. The urinary concentration of solvent (Cu) can be used for the biological monitoring of exposed subjects to evaluate their exposure and correlate with the Threshold Limit Value (TLV) during the working day. The authors report some results obtained with workers occupationally exposed to solvents. The results concern the correlation between urinary concentration (Cu, micrograms/L) vs. average environmental concentration (Ci, mg/m3) measured in the breathing zone. For each solvent studied (acetone, 2-cyclohexane, 1,2-dichloropropane, n-hexane, methyl ethyl ketone, perchloroethylene, styrene, toluene, 1,1,1-trichloroethane) the authors propose a Biological Equivalent Exposure Limit (BEEL) corresponding to the environmental TLV.

The urine/air and blood/urine partition coefficients (lambda) of 43 commonly employed organic solvents (Aliphatic, Cyclic, Aromatic and Halogenated Hydrocarbons, Ketones, Alcohols and Esters) are reported. The analyses were performed by the multiple equilibration method (constant pressure method) using a Hewlett-Packard 5880 gas chromatograph. The lambda values proposed can be employed in the field of biological monitoring of subjects occupationally exposed to solvents vapors.

Some advantages of biological compared with environmental monitoring and some preparatory steps and difficulties to be overcome during the planning of a biological monitoring program are firstly discussed. Then the biological compartments, their peculiarities and their use in the field of biological monitoring are described. The problem concerning the biological thresholds of the reference normal values and the biological limits corresponding to environmental limits (biological equivalent limits, BEL) is the next topic, followed by the description of the methods for measuring the BELs (in case of linear regression between biological and environmental values) and of the methods for the upper and lower confidence limits (UCL, LCL) of a biological value. They are to be used for a decision of compliance or noncompliance biological exposure. Finally some ways of using biological UCL-LCL and variation coefficients during cross-sectional and longitudinal studies (biological monitoring strategies) are shown.

The authors report the parameters which rule the absorption and elimination of polluting solvent vapours in exposed subjects (Ventilation, Pulmonary Capillary Flow, Solubility Coefficients, Environmental Concentrations, Exposure Times). These parameters are included in the equations showing the absorption and elimination indexes and lung clearances. Some methods to measure the Solubility Coefficients of inert gases in biological media and the values referring to 51 industrial solvents, commonly employed or important from the toxicological point of view, are described. Finally the Authors report some experimental results obtained in exposure chamber on volunteers, and in occupationally exposed subjects directly in workplaces. The results are discussed stressing their practical usefulness in the field of biological monitoring, industrial hygiene and in preventive medicine.

The aim of the present work is to determine p-DCB concentration in the urine of exposed workers and to verify a possible correlation with the environmental exposure. The authors studied four subjects exposed to different p-DCB environmental concentrations during a working week. The measurement of the substances was performed by means of a Hewlett-Packard 5880 A gas-chromatograph supplied with a Hewlett-Packard 5970 A Mass Selective Detector. The analysis was performed by a head space method (after determining the urine/air partition coefficient (lambda) by the multiple phase equilibration method). The lambda value (urine/air) of p-DCB is 10.8. The Authors found a significant relationship between the difference of p-DCB urinary concentration at the beginning and end of a daily work delta Cu (microgram/l) and the p-DCB environmental concentration C-I (mg/m3) (r = 0.64) (P less than 0.01); delta Cu = 0,48C-I + 15.61. We found that with an environmental exposure of 44.7 mg/m3 median value (geometrical deviation 1.15) there is an increase of p-DCB concentration in the urine of workers during the working week. For a daily environmental exposure of 450 mg/m3 (ACGIH TLV, 1984), we think that it is possible to propose a Biological Exposure Index (B.E.I.) of 250 micrograms/l as difference between beginning and end of a daily work.

A list of industrial solvents largely employed and produced in Italy (and somewhere else too) is presented. Using two methods previously described, blood/air partition coefficient of such solvents have been measured. Then a discussion is made about the possibility of their employment in the field of biological monitoring of subjects professionally exposed to solvent vapours.

Solubility coefficients of 21 organic industrial solvents of toxicological importance are presented. Using a multiple phase equilibration method, blood/air partition coefficients (lambda) of such substances have been measured. The lambda-values proposed can be employed in the field of biological monitoring of subjects professionally exposed to solvent vapours.

The physical demand in the workplaces can be different depending on each specific job. This involves that workers exposed to the same environmental level of an airborne can absorb different amounts of it depending on their pulmonary ventilation. Starting from the relationship between the uptake (U) and the urinary concentration (Cu) of 6 solvents (Acetone, Styrene, Xylenes, Toluene, Methylchloroform, Tetrachloroethylene) and from the equation expressing their lung uptake the expected values of a biological index after a given time of exposure can be derived. Such values are a function not only of the environmental levels of exposure (CI) but also of the pulmonary ventilation (V) (V--dependent solvents) and of the retention index (R) (V--R--dependent solvents).

A new alveolar air sampler is described and tested; it can be used in monitoring subjects exposed to gas and vapours in their working places. The tests were made under different experimental conditions, using both vapours of industrial solvents as acetone, ethanol, trichloroethylene, methyl ethyl ketone, n-hexane, ethyl acetate and respiratory gas (O2, CO2).

Fifteen human volunteers were exposed to tetrachloroethylene (perchloroethylene, tetrachloroethene) vapor at 3.6-316 mg/m3 for 2-4 hr at rest (10 cases) and during light physical exercise (5 cases). Subsequently, 55 workers who were occupationally exposed to tetrachloroethylene in eight commercial dry cleaning facilities were studied (median value, 66 mg/m3; geometric standard deviation, 3.15 mg/m3). In both the experimentally exposed subjects and occupationally exposed workers the urinary concentration of tetrachloroethylene showed a linear relationship to the corresponding environmental time-weighted average concentration. The findings indicate that the urinary concentration of tetrachloroethylene can be used as an appropriate biological exposure indicator. In occupationally exposed subjects performing moderate work, the urinary tetrachloroethylene concentration corresponding to the time-weighted average of the threshold limit value proved to be 120 mcg/L and its 95% lower confidence limit (biological threshold) 100 mcg/L. The effects of workload on the tetrachloroethylene urinary elimination are also accounted for.

Longitudinal changes in some respiratory parameters (FEV1 and VC) have been examined in a sample of cement workers (163 male subjects differently exposed to cement dusts); the subjects have been surveyed over a period of 10 years performing yearly spirometric tests (Vital capacity--VC and Forced Expiratory Volume in 1 second--FEV1 measurements). Three possible risk indicators have been considered: occupational exposure, smoking habit and age. 65.6% and 60.7% of the cases showed significant individual annual decreases of VC and FEV1 throughout the time of follow up. According to our results the occupational risk indicator has not significantly influenced the normal trend of decreases of the respiratory parameters; instead age brings about an increase of longitudinal changes of VC and smoke habit an increase of longitudinal changes of FEV1, (but only in the younger group, people less than forty years old). 16 subjects characterized by abnormal losses (more than 100 ml/year) have been selected as "VC-FEV1, losers".