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At least 343 records · Page 19Linked to original sources
PubMed2004

Solvent-specific photolytic behavior of octachlorodibenzo-p-dioxin.

The photolysis of octachlorodibenzo-p-dioxin (OCDD) was investigated in various organic solvents under lambda > 300 nm irradiation. The rates of OCDD photolysis were highly solvent-specific. OCDD was photodegraded rapidly in toluene, n-hexane, CCl4, and 1-octanol, whereas it underwent negligible photodegradation in acetonitrile, acetone, and methanol. Both OCDD photolysis and fluorescence emission did not take place in very polar solvents because polar solvent molecules efficiently quenched the excited OCDD (OCDD*). The addition of acetonitrile to an OCDD solution in toluene rapidly quenched both the fluorescence emission and the photolysis rate, which can be described by Stern-Volmer analysis. The efficient photolysis in nonpolar (or less polar) solvents seems to be mediated through a charge-transfer path where the solvent and OCDD* act as an electron donor and acceptor, respectively. However, OCDD photolysis in CCl4 seems to represent the opposite case in which the solvent is an electron acceptor and OCDD* is an electron donor. Hammett sigma constants that approximately represent the electron-donating power in structurally related aromatic solvents show a good correlation with the photolysis rates. We propose that the solvent specificity in OCDD photolysis is mainly ascribed to the difference in the electron donating (or accepting) tendency among various solvents. When triethylamine that easily donates an electron to form a charge-transfer exciplex with OCDD* was added, a marked enhancement in the photolysis rate was observed.

Electrons↗
PubMed2003

Mobile phase compensation to improve NMR spectral properties during solvent gradients.

A solvent compensation method based on flow injection analysis is used to obtain high quality nuclear magnetic resonance (NMR) spectra during solvent gradients. Using a binary solvent system containing D2O and CD3OD, NMR line broadening and chemical shift changes are observed with a 10% methanol per min solvent composition gradient. However, by creating a second equal but reverse gradient and combining the two solvent gradients before the NMR detector, the composition of solvent reaching the NMR flow cell is kept constant. We demonstrate a system using flow injection analysis of combining solvent gradients and show constant NMR spectral performance as a function of time as the combined flow has a constant solvent composition irrespective of the initial solvent gradient. Using this approach, methods can be developed to measure high quality NMR spectra during on-flow gradient LC-NMR experiments. The ultimate ability of this approach depends on the ability to compensate for the disturbance of the solvent gradient and reverse gradient by a pair of LC columns (the analytical and reverse gradient columns).

Chromatography, High Pressure Liquid↗
PubMed2003

Membrane separation in green chemical processing: solvent nanofiltration in liquid phase organic synthesis reactions.

This paper describes ideas together with preliminary experimental results for applying solvent nanofiltration to liquid phase organic synthesis reactions. Membranes for organic solvent nanofiltration have only recently (during the 1990s) become available and, to date, have been applied primarily to food processing (vegetable oil processing, in particular) and refinery processes. Applications to organic synthesis, even at a laboratory feasibility level, are few. However, these membranes have great potential to improve the environmental performance of many liquid phase synthesis reactions by reducing the need for complex solvent handling operations. Examples that are shown to be feasible are solvent exchanges, where it is desired to swap a high molecular weight molecule from one solvent to another between separate stages in a complex synthesis, and recycle and reuse of homogeneous catalysts. In solvent exchanges, nanofiltration is shown to provide a fast and effective means of swapping from a high boiling point solvent to a solvent with a lower boiling point-this is a difficult operation by means of distillation. Solvent nanofiltration is shown to be able to separate two distinct types of homogeneous catalysts, phase transfer catalysts and organometallic catalysts, from their respective reaction products. In both cases the application of organic solvent nanofiltration allows several reuses of the same catalyst. Catalyst stability is shown to be an essential requirement for this technique to be effective. Finally, we present a discussion of scale-up aspects including membrane flux and process economics.

Biotechnology↗
PubMed1991

Spectroscopic observation of solvent interaction with selected retinal Schiff bases.

Iodide salts of several N-retinylidenedialkylamines were prepared and their UV-VIS spectra recorded. Their lambda max values increased as the number of hydrogen atoms on the carbons alpha to nitrogen increased. In separate experiments, iodide salts of N-retinylidene-n-butylammonium (1) and N-retinylidene-n-butylmethylammonium (2) were prepared, and their excitation energies (delta E) were measured in selected solvents of varying dielectric constant (epsilon). Data from each compound gave a straight line which converged at epsilon = 0. On the other hand, when delta E values of the iodide and bromide of 2 were plotted vs solvent epsilon, parallel rather than convergent lines were obtained. When lambda max values of 1 and 2 were measured in a greater number of solvents, the solvents fell into four main groups. The first group, regular solvents, are rigid, have fixed dipoles, neither donate nor accept H-bonds, and the delta E of 1 and 2 decreases linearly as solvent epsilon increases. This line for 2 is taken as a standard against which other solvents are judged. A second class of solvents that are good H-bond donors like CHCl3, whose dipole moment coincides with the C-H bond axis, is located in an area below the standard line. A third group, nucleophilic solvents like tetrahydrofuran, whose dipole moment is coincident with a strongly nucleophilic oxygen atom are good H-bond acceptors and are found above the standard line. Solvents with unpredictable spectroscopic behavior are classed as anomalous.

Bromides↗
PubMed2002

Mechanisms of solvent tolerance in gram-negative bacteria.

Organic solvents can be toxic to microorganisms, depending on the inherent toxicity of the solvent and the intrinsic tolerance of the bacterial species and strains. The toxicity of a given solvent correlates with the logarithm of its partition coefficient in n-octanol and water (log Pow). Organic solvents with a log Pow between 1.5 and 4.0 are extremely toxic for microorganisms and other living cells because they partition preferentially in the cytoplasmic membrane, disorganizing its structure and impairing vital functions. Several possible mechanisms leading to solvent-tolerance in gram-negative bacteria have been proposed: (a) adaptive alterations of the membrane fatty acids and phospholipid headgroup composition, (b) formation of vesicles loaded with toxic compounds, and (c) energy-dependent active efflux pumps belonging to the resistance-nodulation-cell division (RND) family, which export toxic organic solvents to the external medium. In these mechanisms, changes in the phospholipid profile and extrusion of the solvents seem to be shared by different strains. The most significant changes in phospholipids are an increase in the melting temperature of the membranes by rapid cis-to-trans isomerization of unsaturated fatty acids and modifications in the phospholipid headgroups. Toluene efflux pumps are involved in solvent tolerance in several gram-negative strains, e.g., Escherichia coli, Pseudomonas putida, and Pseudomonas aeruginosa. The AcrAB-TolC and AcrEF-TolC efflux pumps are important for n-hexane tolerance in E. coli. A number of P. putida strains have been isolated that tolerate toxic hydrocarbons such as toluene, styrene, and p-xylene. At least three efflux pumps (TtgABC, TtgDEF, and TtgGHI) are present in the most extensively characterized solvent-tolerant strain, P. putida DOT-T1E, and the number of efflux pumps has been found to correlate with the degree of solvent tolerance in different P. putida strains. The operation of these efflux pumps seems to be coupled to the proton motive force via the TonB system, although the intimate mechanism of energy transfer remains elusive. Specific and global regulators control the expression of the efflux pump operons of E. coli and P. putida at the transcriptional level.

Adaptation, Physiological↗
PubMed2003

The acid-base equilibrium constants of some azine compounds in various aqueous-organic solvent mixtures.

The acid dissociation constants of the protonated form of some azine compounds (acridine, acridine orange and neutral red, BH+) were determined pH-metrically at 25 degrees C and at the constant ionic strength I = 0.1 mol l(-1) (KNO3) in pure water as well as in various aqueous mixtures having different proportions (w/w%) of organic solvents. The organic solvents used are methanol, ethanol (as amphiprotic solvents), N,N-dimethylformamide, dimethylsulfoxide (as dipolar aprotic solvents) and acetonitrile (as a low basic solvent). The results obtained indicated that the pKa values decrease as the content of the organic solvent in the medium is increased. It is deduced that, the major effect responsible for this behaviour is the differences in stabilization of the free base (B) by dispersion forces and of the proton by its interaction with solvent and water molecules in aqueous-organic solvent mixtures (ion-solvent interaction). Moreover, it is concluded that the ability of the solvent to accept hydrogen bond from the protonated form (BH+) contributes significantly to the deprotonation process of the compounds.

Acridine Orange↗
PubMedDate not supplied

[Solvent pollution in shoe factories].

In order to study solvent exposure in shoe factories, 43 kinds of glues and 22 solvent products used in footwear manufacturing were analyzed. A gas chromatographic spectrometric method was used to identify the mixtures of solvents contained in glues and their diluents. Acetone, ethylacetate and cyclohexane were the solvents more frequently found in glues. Cyclohexane represented on average about 40% of the solvent mixture. Methyl ethyl ketone, 3-methylpentane and 2-methylpentane were often present in glues (45-52% of the samples), but only in a few cases were they associated with n-hexane. N-hexane and methylcyclopentane were found in 32% of the glue samples. N-hexane represented 47% of the solvents only in one glue. Most of the glues contained less than 10% n-hexane. Other solvents (dichloropropane, toluene, trichloroethane, butyl acetate, iso-butyl acetate and 2,2-dimethylbutane) were found in few glue samples or in low percentages. The 22 solvents used as glue diluents were mainly acetone, ethylacetate, dichloromethane and methyl ethyl ketone. The results suggest that solvent exposure in shoe factories has changed compared with data reported about 10 years ago. Biological monitoring of shoe factory workers should measure exposures to the specific solvents found in each factory, especially acetone, cyclohexane, ethylacetate and methyl ethyl ketone.

Adhesives↗
PubMed1988

The continuing problem of youthful solvent abuse in New York State.

The major finding in the comparison of surveys of New York State secondary school students is the increasing use of solvents in this population over time. What in 1974-75 seemed to be limited use, by 1983 was found to be of widespread use. Very much like the survey of 1974-75 and the findings in the literature, age of first use together with the recentness of use appears to cluster in the preteens or the early teen years and tapers off during the teen years. Of interest is the fact that, along with the general upward rate of use over the surveys, those 18 years or older also show an upward trend. Some evidence in the recent literature indicates that adults, too, are found to have a problem with inhalants. Similar to the 1974-75 survey, but unlike findings in the literature, males and females continue to show similar rates of solvent use. Although males do generally surpass females in these use rates, the differences are usually not significant. In light of the literature on solvent abuse among Hispanic youth, the 1978 and 1983 surveys indicated mixed findings. Hispanic students in New York City consistently showed intermediate levels of solvent use; whereas, in 1983, Hispanic students residing in areas of the state outside of New York City showed excessive rates of solvent use. To the extent that the problem of acculturation among poor Hispanic youth may contribute to solvent abuse, an explanation may be found in the contrasts between living in New York City and living in the rest of the State. In New York City, which has an extremely large Hispanic population (about 20 percent of the population), feelings of isolation and cultural distance may not be so profound. In the rest of the state, where the proportion of Hispanics is quite small (about 2 percent of the population), these cultural problems may be more of a factor. Reasons, however, for the extraordinary increase in solvent use among those Hispanic youth, specifically between 1978 and 1983, are difficult to offer. Again, very similar to the 1974-75 findings, the 1978 and 1983 surveys found a strong relationship between solvent use and poor academic performance. Furthermore, the early findings relating to solvent use to a lack of family cohesion was supported by the 1978 survey where comparable information was gathered. The pattern of drug-using or polydrug use found among solvent users in the 1974-75 survey was underscored by the findings in the subsequent surveys.(ABSTRACT TRUNCATED AT 400 WORDS)

Administration, Inhalation↗
PubMed1983

[Effect of various solvents on the extraction of protein fractions of beans (Phaseolus vulgaris)].

A study was carried out to determine the effect of different solvents on the extraction of protein fractions in beans. Black bean protein was extracted with the following solvents: distilled water, 0.01 M sodium hydroxide, 0.05 M sodium chloride, and 70% ethanol. By using each solvent under different conditions, it was possible to establish the optimum ones for the best extraction and fractionation of proteins from leguminous seeds. These conditions were the following: one hour agitation at room temperature, three successive extractions with the same solvent, and a ratio of solid to solvent of 1:20 W/V. The effect of 24 different sequences of solvents upon the extraction of protein was also investigated. From the extraction point of view, the best sequence of solvents for extracting the protein was that where NaOH constituted the first solvent used; this sequence, however, has the disadvantage of extracting all the protein from the seed, making it impossible to separate other protein fractions by another solvent. If the purpose of the extraction is to separate different protein fractions, the best sequence of solvents is distilled water or sodium chloride in the first place, followed by ethanol and sodium hydroxide. The need for using standardized methodology for the fractionation of protein from seeds in order to obtain comparable data between research laboratories is emphasized.

Ethanol↗
PubMed1994

Has the Scandinavian solvent syndrome controversy been solved?

This article discusses the "Scandinavian solvent syndrome" and reviews epidemiologic studies on occupational solvent exposure and two related outcomes. High cumulative exposure to organic solvents in the 1960-1970s was related to early retirement from neuropsychiatric disorders, but solvent exposure alone was an unlikely cause of more severe dementia conditions. Heavy alcohol consumption seemed to modify the effect on solvent-related brain disorders strongly, but no reports exist of alcohol consumption as a confounding factor. Many cross-sectional and experimental studies support functional impairment from high solvent exposure. The mists and myths around the "Scandinavian solvent syndrome" can now be cleared up: it was not a uniform syndrome, it might be reversible in many cases, it is not confined to the Scandinavian countries, the risk of more severe dementia is substantial for combined high solvent exposure and excessive alcohol consumption, and many solvent-exposed workers receive early retirement due to solvent-related neuropsychiatric disorders.

Air Pollutants, Occupational↗
PubMed2006

Electron transfer in a radical ion pair: quantum calculations of the solvent reorganization energy.

Results are presented for an investigation of intermolecular electron transfer (ET) in solution by means of quantum calculations. The two molecules that are involved in the ET reaction form a solvent-separated radical ion pair. The solvent plays an important role in the ET between the two molecules. In particular, it can give rise to specific solute-solvent interactions with the solutes. An example of specific interactions is the formation of a hydrogen bond between a protic solvent and one of the molecules involved in the ET. We address the study of this system by means of quantum calculations on the solutes immersed in a continuum solvent. However, when the solvent can give rise to hydrogen bond formation with the negatively charged ion after ET, we explicitly consider solvent molecules in the solute cavity, determining the hydrogen bond energetic contribution to the overall interaction energy. Solute-solvent pair distribution functions, showing the different arrangement of solvent molecules before and after ET in the first solvation shell, are reported. We provide results of the solvent reorganization energy from quantum calculations for both the two isolated fragments and the ion pair in solution. Results are in agreement with available experimental data.

Journal Article↗
PubMed2004

Monte Carlo simulation of dendrimers in variable solvent quality.

We study via lattice Monte Carlo simulation and Flory theory the properties of g=1-6 dendrimers in variable solvent quality. For all the generations studied, we find that the radius of gyration R(g) collapses significantly (factor of 2) going from athermal to extreme poor solvent conditions, indicating that varying solvent quality is an effective means of controlling dendrimer size. We also find that in athermal, theta, and extreme poor solvent conditions, the radius of gyration of dendrimers scales with the total number of monomers roughly as R(g) approximately N(1/3). However, a more careful analysis shows that in athermal and theta solvents, there is, in fact, a small but systematic deviation of R(g) from R(g) approximately N(1/3) scaling and the simulation data is described better by the Flory theory prediction of R(g) approximately N(1/5)[(g+1)m](2/5) in athermal solvents and R(g) approximately N(1/4)[(g+1)m](1/4) in theta solvents. We also find for our simulation data that stronger deviations from constant density scaling are possible, with scaling behavior as shallow as R(g) approximately N(0.26) possible for solvent conditions in between theta and the completely collapsed state. It is evident therefore that dendrimers do not obey (or even approximately obey) R(g) approximately N(1/3) scaling under all solvent conditions. Under all solvent conditions, we find that the intramolecular density is dense corelike (i.e., the density maximum is in the interior of the dendrimer) and terminal groups are delocalized throughout the dendrimer.

Journal Article↗
PubMed2002

Can a continuum solvent model reproduce the free energy landscape of a beta -hairpin folding in water?

The folding free energy landscape of the C-terminal beta-hairpin of protein G is explored using the surface-generalized Born (SGB) implicit solvent model, and the results are compared with the landscape from an earlier study with explicit solvent model. The OPLSAA force field is used for the beta-hairpin in both implicit and explicit solvent simulations, and the conformational space sampling is carried out with a highly parallel replica-exchange method. Surprisingly, we find from exhaustive conformation space sampling that the free energy landscape from the implicit solvent model is quite different from that of the explicit solvent model. In the implicit solvent model some nonnative states are heavily overweighted, and more importantly, the lowest free energy state is no longer the native beta-strand structure. An overly strong salt-bridge effect between charged residues (E42, D46, D47, E56, and K50) is found to be responsible for this behavior in the implicit solvent model. Despite this, we find that the OPLSAA/SGB energies of all the nonnative structures are higher than that of the native structure; thus the OPLSAA/SGB energy is still a good scoring function for structure prediction for this beta-hairpin. Furthermore, the beta-hairpin population at 282 K is found to be less than 40% from the implicit solvent model, which is much smaller than the 72% from the explicit solvent model and approximately equal 80% from experiment. On the other hand, both implicit and explicit solvent simulations with the OPLSAA force field exhibit no meaningful helical content during the folding process, which is in contrast to some very recent studies using other force fields.

Animals↗
PubMed1993

Entropy maximization constrained by solvent flatness: a new method for macromolecular phase extension and map improvement.

A practical generally applicable procedure for exponential modeling to maximum likelihood of macromolecular data sets constrained by a moderately large basis set of reliable phases and a molecular envelope is described, based on the computer program MICE [Bricogne & Gilmore (1990). Acta Cryst. A46, 284-297]. Procedures were first tested with simulated data sets. Exact and randomly perturbed amplitudes and phases were generated, together with a known envelope for solvent-free protein and for protein in an electron-dense crystal mother liquor typical of many real protein crystals. These experiments established useful guidelines and values for various parameters. Tests with basis sets chosen from the largest amplitudes indicate that exponential models with considerable correct extrapolated phase and amplitude information can be constructed from as few as 16% of the total number of reflections, with mean phase errors of about 30 degrees, at resolution limits of either 5 or 3 A. When the shape of the solvent channels in macromolecular crystals is known, it offers an important additional source of information. MICE was, therefore, adapted to average the density outside the molecular boundary defined by an input envelope. This flattening process imposes a uniform density distribution in solvent-filled channels as an additional constraint on the exponential model and is analogous to the treatment of solvent in conventional solvent flattening. Experimental data for cytidine deaminase, a structure recently solved by making extensive use of conventional solvent flattening, provides an example of the performance of maximum-entropy methods in a real situation and a compelling comparison of this method to standard procedures. Exponential models of the electron density constrained by the most reliable phases obtained by multiple isomorphous replacement with anomalous scattering (MIRAS) (figure of merit > 0.7, representing 34% of the total number of reflections) and by the envelope give rise to centroid electron-density maps which are quantitatively superior by numerous statistical criteria to conventionally solvent-flattened density. Similarity of these maps to the 2F(obs) - F(calc) map calculated with phases obtained after crystallographic refinement of the model implies that maximum-entropy extrapolation provides better phases for the remaining 66% of the reflections than the original centroid MIRAS distributions. Importantly, the solvent-flattened electron density, although it did permit interpretation of the map which was not readily accomplished with the MIRAS map, contains substantial errors. It is proposed that errors of this sort may account for previously noted deficiencies of the solvent-flattening method [Fenderson, Herriott & Adman (1990). J. Appl. Cryst. 23, 115-131] and for the occasional tendency of incorrect interpretations to be 'locked in' by crystallographic refinement [Brändén & Jones (1990). Nature (London), 343, 687-689, and references cited therein]. Solvent flattening with combined maximization of entropy and likelihood represents a phase-refinement path independent of atomic models, using the experimental amplitudes and the most reliable phases. It should, therefore, become a valuable and generally useful procedure in macromolecular crystal structure determination.

Journal Article↗
PubMed2004

Force between unlike star-polymers versus the solvent quality.

We re-examine here the computation of the effective force between two star-polymers A and B of different chemical nature, which are immersed in a common solvent. This force originates from the excluded-volume interactions and chemical segregation. We assume that the solvent quality may be different for the two unlike star-polymers, that is the solvent can be 1) a good solvent for A and B, 2) a good solvent for A and a Theta-solvent for B, or 3) a Theta-solvent for the two polymers. The purpose is a quantitative study of the effect of the solvent quality on the effective force, which is a function of the center-to-center distance. Calculations are achieved using the renormalization theory applied to the Edwards continuous model. We first show that, when the mutual interactions are present, the effective force decays as the inverse of distance, but with a universal amplitude depending on the solvent quality. Second, we demonstrate the existence of three kinds of forces related to situations 1), 2) and 3) described above, and give the third-order epsilon-expansions (epsilon = 4 - d, 4 is the critical dimension) of the corresponding amplitudes. These series can be resummed using the Borel-Leroy techniques to obtain the best three-dimensional values for the expected force amplitudes. Finally, this work must be regarded as a natural extension of a published one which dealt with the same problem, but where the solvent was assumed to be good for the two unlike star-polymers.

Journal Article↗
PubMedDate not supplied

Pregnancy outcome following gestational exposure to organic solvents: a prospective controlled study.

CONTEXT: Numerous women of childbearing age are exposed occupationally to organic solvents. Previous retrospective studies have reported conflicting results regarding teratogenic risk. OBJECTIVE: To evaluate pregnancy and fetal outcome following maternal occupational exposure to organic solvents. DESIGN: A prospective, observational, controlled study. SETTING: An antenatal counseling service in Toronto, Ontario. PATIENTS: One hundred twenty-five pregnant-women who were exposed occupationally to organic solvents and seen during the first trimester between 1987 and 1996. Each pregnant woman who was exposed to organic solvents was matched to a pregnant woman who was exposed to a nonteratogenic agent on age (+/-4 years), gravidity (+/-1), and smoking and drinking status. MAIN OUTCOME MEASURE: Occurrence of major congenital malformations. RESULTS: Significantly more major malformations occurred among fetuses of women exposed to organic solvents than controls (13 vs 1; relative risk, 13.0; 95% confidence interval, 1.8-99.5). Twelve malformations occurred among the 75 women who had symptoms temporally associated with their exposure, while none occurred among 43 asymptomatic exposed women (P<.001). (One malformation occurred in a woman for whom such information was missing.) More of these exposed women had previous miscarriage while working with organic solvents than controls (54/117 [46.2%] vs 24/125 [19.2%]; P<.001). However, exposed women who had a previous miscarriage had rates of major malformation that were similar to exposed women who had no previous miscarriage. CONCLUSIONS: Occupational exposure to organic solvents during pregnancy is associated with an increased risk of major fetal malformations. This risk appears to be increased among women who report symptoms associated with organic solvent exposure. Women's exposure to organic solvents should be minimized during pregnancy. Symptomatic exposure appears to predict higher fetal risk for malformations.

Abortion, Spontaneous↗
PubMed1985

Solvent interactions with test compounds and recommendations for testing to avoid artifacts.

Reports in the literature describing artifactual results owing to interactions of test materials with solvents are becoming more frequent. The present study was initiated to examine possible interactions of 1,1,3-trichloro-, 1,1,3,3-tetrachloro-, pentachloro- and hexachloroacetones with different solvents, since certain solvent effects with the last compound have been shown previously. Quantitative differences in levels of mutagenic potency were found for tri-, tetra-, and pentachloroacetone, dissolved in acetone or dimethyl sulfoxide (DMSO). On the other hand, hexachloroacetone without solvent was mutagenic, and this activity was enhanced when it was dissolved in DMSO; in acetone it was not mutagenic. A time-dependent reaction of hexachloroacetone with DMSO was the only test material-solvent interaction found in this study. The results show clearly that DMSO is not an appropriate solvent for hexachloroacetone. On the basis of these and previous results, we recommend consideration of the following strategy to help prevent reporting of artifactual results owing to interaction with solvents: Results from initial screening experiments should be confirmed in repeat experiments using a different solvent; and a different solvent should be used in confirming the findings of other investigators. Differences in results would indicate a need for further study.

Acetone↗
PubMed1992

Neurotoxicity of solvent mixtures in spray painters. I. Study design, workplace exposure, and questionnaire.

A multidisciplinary cross-sectional study was carried out in 105 spray painters with long-term solvent exposure (10-44 years) and in 58 control subjects not exposed to solvents. By means of air monitoring the solvent concentrations in the ambient air during spray painting were determined using charcoal and silicagel tubes with pumps and passive samplers. In general, the air concentrations of the individual compounds did not exceed the current limit values (MAK values). Aromatic hydrocarbons like toluene, xylene, ethylbenzene, trimethylbenzene, aliphatic hydrocarbons (e.g., heptane) and acetates (ethylacetate, butylacetate) were determined to be important components of paint solvents. However, in unfavorable work conditions the "exposure index" could exceed the permissible limits two or three times. To assess the body solvent load at the time of examination, biological monitoring (BM) was performed. The main finding was that there was no evidence of neurotoxicologically relevant solvent exposure. Only in the case of methyl hippuric acid in urine spot samples did the spray painters show a higher mean value (80 mg/l) than control subjects (below 20 mg/l), indicating recent xylene exposure. Elevated urinary chromium concentrations (maximum value 29 micrograms/l) were found in 28 spray painters as a result of using zinc chromate-containing wash primers without taking protective measures. To assess the degree of past solvent exposure a special questionnaire was used. This included variables like duration and amount of solvent exposure, the presence of a technical ventilation system, health complaints during painting, etc. Additionally, three "solvent exposure indices'' (SEI) were calculated and used for evaluation of "dose-effect relationships.''(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗