The urinary concentration of solvents as a biological indicator of exposure: proposal for the biological equivalent exposure limit for nine solvents

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.

[Proposal of the biological monitoring of inhalation anesthetics]

The long-term occupational exposure to inhalation anaesthetics might represent a health hazard; mainly it may have an adverse effect on the reproductive outcome. Nitrous oxide is the anaesthetic employed in the largest amount during general anaesthesia and it can be used as an indicator of occupational exposure to all the components the mixture; but if the pattern of dispersion of them (when leaking into the operating theater) are not the same, two indicators should be used: N2O (gas) + another component the mixture (vapour). Our results concern practically 5 points: --Analysis of N2O by means of a diffusive personal sampler (comparison with a conventional sampling method) --Analysis of N2O in urine collected after 4 hours of exposure during routine anaesthetic work (headspace method) --Comparison of environmental and biological data concerning N2O --Comparison of environmental and biological data concerning a component of the anaesthetic mixture, forane --Proposal of biological exposure indices for nitrous oxide and forane. A close relationship between air and urine was found in 363 subjects occupationally exposed to N2O and 45 subjects exposed to forane (r: 0.95 and 0.90 respectively). On the basis of such a relationship the biological exposure index for N2O corresponding to an ambient concentration of 100 ppm (European limit) turned out to be 55 micrograms/L; the ones for forane corresponding to ambient concentrations of 2 or 10 ppm are respectively 3.4 or 14.5 micrograms/L (urinary concentrations in samples collected after 4 hours of exposure).

[Use of gas chromatography with flame ionization (GC-FID) in the measurement of solvents in the urine]

The urinary concentration of some solvents (acetone, cyclohexane, 1,2 dichloropropane, n-hexane, methyl ethyl ketone, perchloroethylene, styrene, toluene, 1,1,1, trichloroethane) was measured by means of a gas chromatography Hewlett-Packard 5890 supplied with a flame ionization detector (GC-FID, DANI HS 3950). The coefficient of variation of the method was lower than 5%. The sensitivity of the GC-FID was very similar to what of mass spectrometer detector (GC-MSD, HP 5970 A).

Urinary elimination of acetone in experimental and occupational exposure

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.

[Relationship of environmental levels, respiratory absorption and urinary concentrations of various solvents: effects of work load]

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).

Effects of dimethylformamide (DMF) on coagulation and platelet activity

The effects of dimethylformamide (DMF) on hemostatic functions, especially on platelet activity, were examined both in vitro and in vivo in 15 workers exposed to DMF (27 mg/m3, median value). Twenty-eight control subjects who were not exposed to DMF, but comparable for age, anthropometric data, and smoking habits, were also studied. Workers exposed to DMF showed a decrease in the number of platelets and had longer coagulation times, probably due to a change caused by DMF on the membrane receptor of platelets and on the phospholipid components of the clotting system.

Urinary elimination of styrene in experimental and occupational exposure

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.

[Exposure to acetone: experimental study of absorption and pulmonary elimination in normal subjects]

Alveolar (CA) and mixed expired air (CE) acetone concentrations were measured in 15 healthy volunteer subjects, exposed to acetone (CI) in an exposure chamber (exposure range: 48-565 mg/m3) both at rest and during exercise (50 W). The Relative Uptake (R = 1-CE/CI) was 0.54 at rest (120' and 240') and 0.55 during exercise (120', 50 W). Ca:CI ratio was 0.24 at rest. CE:CI and CA:CI ratio was constant throughout the exposure time, both at rest and during exercise.

Urinary elimination of p-dichlorobenzene (p-DCB) and weighted exposure concentration

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.

n-Hexane urine elimination and weighted exposure concentration

The concentration of n-hexane in urine was determined in 30 subjects occupationally exposed to n-hexane (median value 59.6 mg/m3) in a shoe factory. The measurement of the substance was performed by means of a Hewlett-Packard 5880 gas chromatograph supplied with a Hewlett-Packard 5970 Mass Selective Detector. The analyses were performed by the head space method (constant volume method, after determination of the urine partition coefficient by the multiple phase equilibration method). The authors found a significant correlation between the n-hexane urine concentrations (microgram/l, Cu) and the n-hexane environmental concentrations (mg/m3, Ci) (r = 0.84; Cu = 0.0669 X Ci + 0.8396).

[Stability of esters in the blood in vitro]

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.

[Changes induced by dimethylformamide on platelet function and coagulation activity]

The effect of Dimethylformamide on platelet function and on clotting system has been studied on eight workers exposed to the product, widely used in industry as a solvent of acrylic resins. A significant reduction of the number of the platelets and a drawing out of PTT and PT has been noticed. Such informations has been explained as chronical peripheral use or as modification of phospholipid components induced by DMF instead of synthesis defect, as no significant variation of the fibrinogen and of AT III values, proteins synthetized by liver, has been observed. The platelet aggregation has pointed out, in vivo, a reduction of ADP aggregation in the exposed subjects; in vitro, increasing quantities have determined an increasing reduction of the primary ADP and adrenaline aggregation.

[N-hexane and toluene in the urine of occupationally exposed subjects. Measurement and significance of its presence]

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.

[An open system for exposure to noted and controlled concentrations of aeriform substances]

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 measurement of the solubility coefficients of gases in the blood. III. Other solvents of toxicological importance]

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.

[Measurement of the coefficient of solubility of airborne substances in blood. II. Solvents of wide industrial use]

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.

[Evaluation of a new alveolar air sampler]

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).

[The measurement of the solubility coefficients of aeriforms in the blood or other solvent liquids. I. The methods]

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.

[Determination of urinary phenol by means of HPLC]

We describe the determination of urinary phenol by liquid chromatography with fluorescence detection. The fluorescence response is linear with injected phenol concentration over at least five orders of magnitude. The detection limit is 20 pg which correspond to a minimum detectable concentration of 0.5 mg/l.