Association of exposure to benzene and smoking with oxidative damage to nucleic acids by means of biological monitoring of general population volunteers

In this study, the validation of liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) isotopic dilution method for the determination of benzene and nicotine metabolites in urine was carried out. Limit of detection are 0.026 μg/L for S-phenylmercapturic acid (SPMA), 0.55 μg/L for t,t-muconic acid (t,t-MA), and 12.41 μg/L for the cotinine, and the relative combined uncertainty was also calculated. The study involves 446 healthy volunteer residents since at least 10 years in an area of central Italy. SPMA resulted to be strongly correlated with cotinine (p = 0.75), its concentration in smokers (93) being about ten times than in non/ex-smokers (197/156), while the t,t-MA of smokers is about twice the non/ex-smokers value. A cutoff value for the definition of smoker is set at 100 μg/g creat. Oxidative stress was studied in smokers and non- and ex-smokers by means of the determination of the biomarkers 8-Oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), 8-Oxo-7,8-dihydroguanosine (8-oxoGuo), and 8-Oxo-7,8-dihydroguanine (8-oxoGua): no significant differences were found between smokers and non/ex-smokers, but when subjects are classified according to the cotinine cutoff value, a correlation in smokers' urinary 8-oxodGuo is found with SPMA and cotinine (p = 0.60 and p = 0.57). Results were confirmed by chemometric analysis that also identified the experimental variables most contributing the discrimination as cotinine and t,t-MA.

Oxidative stress biomarkers and otoacoustic emissions in humans exposed to styrene and noise

OBJECTIVE

Evaluating the correlation between otoacoustic emission levels, styrene exposure, and oxidative stress biomarkers concentration in styrene-exposed subjects, to investigate the role of oxidative stress in outer hair cell damage.

DESIGN

Distortion product otoacoustic emissions were measured in the exposed workers and in a control group. Separation between the distortion and reflection otoacoustic components was performed by time-frequency-domain filtering. The urinary concentration of the DNA and RNA oxidation products, namely 8-oxo-7,8-dihydroguanine (oxoGua), 8-oxo-7,8-dihydro-2'-deoxyguanosine (oxodGuo), and 8-oxo-7,8-dihydroguanosine (oxoGuo), were evaluated.

STUDY SAMPLE

Nine subjects exposed to styrene in a fiberglass factory, eight control subjects. The two groups were statistically equivalent in mean age.

RESULTS

Statistically significant differences were found in the distortion component levels between the exposed and the control group. High levels of the oxidative damage biomarkers were found in the workers exposed to high levels of styrene. Significant negative correlation was found between the otoacoustic emission distortion component levels and the concentration of the oxoGuo biomarker.

CONCLUSIONS

Exposure-induced damage of the cochlear amplifier is shown in the mid-frequency range, confirming animal experiments, in which hair cells in the cochlear middle turn were damaged. Hearing damage is consistent with the outer hair cell apoptosis pathway associated with oxidative stress.

Otoacoustic emission sensitivity to exposure to styrene and noise

The ototoxic effect of the exposure to styrene is evaluated, also in the presence of simultaneous exposure to noise, using otoacoustic emissions as biomarkers of mild cochlear damage. Transient-evoked and distortion product otoacoustic emissions were recorded and analyzed in a sample of workers (15 subjects) exposed to styrene and noise in a fiberglass manufacturing facility and in a control group of 13 non-exposed subjects. Individual exposure monitoring of the airborne styrene concentrations was performed, as well as biological monitoring, based on the urinary concentration of two styrene metabolites, the Mandelic and Phenylglyoxylic acids. Noise exposure was evaluated using wearable phonometers, and hearing loss with pure tone audiometry. Due to their different job tasks, one group of workers was exposed to high noise and low styrene levels, another group to higher styrene levels, close to the limit of 20 ppm, and to low noise levels. A significant negative correlation was found between the otoacoustic emission levels and the concentration of the styrene urinary metabolites. Otoacoustic emissions, and particularly distortion products, were able to discriminate the exposed workers from the controls, providing also a rough estimate of the slope of the dose-response relation between otoacoustic levels and styrene exposure.

[Synergistic exposure to noise and styrene and cochlear functionality in a sample of exposed workers: preliminary results]

This study is aimed at testing the cochlear functionality using otoacoustic emissions, analyzing the synergistic effects of simultaneous exposure to noise and organic solvents EBTx on workers of a glass-reinforced plastic products factory. Exposure to organic solvents was assessed using ambiental measurements and evaluation of the salivary concentration. Biological monitoring was performed evaluating the urinary concentration of the styrene metabolites. Statistical analysis shows that otoacoustic tests can discriminate between different exposure groups. Significant differences were found between controls and subjects exposed to high styrene and low noise levels, showing the ototoxic effect (at sub-clinical level) of the styrene exposure.

[Biological monitoring of the PAH exposure in the hardening of metals]

The hardening of metals involves the immersion of hot components in mineral oil with production of aerosols containing PAHs, to wich workers can be exposed. The determination of airborne PAHs and urinary 1-hydroxypyrene (1-OHPy) was performed for a group of workers and the latter resulted within the reference values. However, the average 1-OHPy concentration on metal workers (0.07 microg/g creatinine) was statistically different from the average value obtained for a group of employees (0.03 microg/g creatinine), highlighting the risk of exposure to PAHs. Therefore, being these potentially carcinogenic compounds, interventions were prescribed in order to reduce the risk of occupational exposure.

Determination of free and totalS-phenylmercapturic acid by HPLC/MS/MS in the biological monitoring of benzene exposure

Urinary S-phenylmercapturic acid (SPMA) is a biomarker suggested by the American Conference of Governmental Industrial Hygienists (ACGIH) for assessing occupational exposure to benzene. A possible cause of the miscorrelation between environmental monitoring and biological monitoring for benzene exposure, which many authors complain about, is the existence of a urinary metabolite that turns into SPMA by acid hydrolysis. Forty urine samples were tested to determine which concentration value would correspond to the ACGIH Biological Exposure Index (BEI) of 25 microg g(-1) creatinine if exposure assessment was based on the determination of SPMA after quantitative hydrolysis of its precursor. An aliquot of each sample was hydrolysed with 9 M H2SO4, a second one was brought to pH 2 and a third one was used as it was (free SPMA). SPMA was determined by high-performance liquid chromatography/tandem mass spectrometric technique (HPLC/MS/MS) using an internal standard. The analytical method was validated in the range 0.5-50 microg 1(-1). The average SPMA in pH 2 samples is 45-60% of the total, while free SPMA varies from 1% to 66%. The hydrolysis of pre-SPMA reduces the likelihood of variability in the results by reducing pH differences in urine samples and increasing the amount of measured SPMA. The BEI limit value would be about 50 microg g(-1) creatinine.

[Salivary analyses for biologic monitoring: possibility and perspectives]

The use of saliva for biological monitoring offers several interesting advantages, in terms of cost, non-invasive sampling, no risk of infection and little likelihood of the sample being polluted. Tests for measuring chemicals in saliva are available for many endogenous analytes, and xenobiotics. Saliva tests for inorganic compounds have so far not given satisfactory results, even using highly sensitive methods such as ICP/MS or atomic absorption. However, testing saliva for pesticides holds promise: the close correlation between the plasma compartment and saliva for some of these compounds has led to proposals for assaying diazinon, trichloropyridinol, atrazine, and paraquat, for instance, in saliva as biological indicators of occupational exposure. In industrial settings too significant correlations have been found between blood, urine and saliva assays. Investigations of exposure, for example, to plastifiers (phthalates), methanol, isopropanol and m-xylene have given comparable, equally reliable data, although highly sensitive instrumentation is needed. This approach appears to offer a wide range of applications, and certainly merits further study.

[Study on the interaction between the skin detoxifying enzyme glutathione S-transferase and the substances listed in the CE/39/2000 rules with the "skin" annotation, finalized to the biological monitoring of exposed subjects]

The interaction among chemicals listed in the Directive CE/39/2000 with skin notation and glutathione S-transferase (GSTP1-1) was studied by following two different experimental approaches. The compounds were incubated with the purified GST isoenzyme GSTP1-1 as well as with the human keratinocytes (PR5) selectively expressing GSTP1-1. Some of the molecules affected the enzymatic activity of both the purified and the intracellular GSTP1-1. In particular, 1,2-dichlorobenzene (DCB), ethylbenzene (ETB), cumene, Sulphotep and 2-eptanone (2-EPT) behaved as inhibitors of the purified GSTP1-1 enzyme, with different inhibition properties according to molecular structure. With the exception of Sulphotep showing a Ki value of 0.2 mM, all compounds reported above were characterized by high Ki values (between 2 and 16 mM) and therefore by low affinity towards GSTP1-1. These results make unlikely the use of a biosensor, based on immobilized GSTP1-1, for the detection of these molecules. On the contrary, Sulphotep can be the object of future investigations. It has to be stressed that the above listed compounds were effective on human keratinocytes, at concentrations two order of magnitude lower than that effective on purified GSTP1-1. In particular, cumene and DCB triggered a clear increase of the intracellular GSTP1-1 activity at concentrations lower than 0.1mM. These interesting results let to hypothesize the use of GSTP1-1 present in the keratinocytes as a marker for biological monitoring of workers exposed to these compounds as well as to evaluate the skin permeability of toxic compounds, not yet identified with a skin notation.

[Isotopic dilution HPLC/MS/MS urinary trans, trans-muconic quantitative analysis among refinery workers]

The determination of trans, trans muconic acid (t,t-MA) in human urine, a biomarker suggested by the American Conference of Governmental Industrial Hygienists for occupational benzene exposure, with a limit value of 500 microg/g creatinine, is usually performed by means of gas or liquid chromatographic methods. Almost all the HPLC methods make use of strong ionic exchange cartridges for sample cleaning, reverse phase separation and detection either by UV at lambda = 259 nm or; more recently, by electrospray tandem mass spectrometry: yet, not all of these methods have been validated for quantitative analysis considering also the matrix effect. This paper presents the quantitative analysis of t,t-MA in 94 end-shift urine samples from workers of an oil refinery performed by means of an HPLC/MS/MS analytical method that uses a commercially available deuterium labeled isotope as internal standard, that during the validation has highlited the problem of interferences due to urine ion suppression effect and to the interference from isobaric ions both for the analyte and the internal standared. The following mean values have been obtained: 47.37 microg/g creatinine for non smokers non occupationally exposed to benzene, 97.40 microg/g creatinine for non smokers exposed to benzene, 142.38 microg/g creatinine for smokers non occupationally exposed and 149.08 microg/g creatinine for smokers occupationally exposed to benzene. The results obtained demonstrate that using this analytical method for urinary t,t,MA it is possible to discriminate among groups with different levels of benzene exposure, due to all the possible benzenene sources: environmetal, occupational, due to smoking, and their possible combinations.

[Feasibility study of biological monitoring of chemical agents by means of evaluation of the effects on their in vitro effects on the complement system]

Immunological methods for the study of the plasma complement system have been standardized in order to be good and reproducible indicators of some biological effects of the substances under study in in vitro experiments. The substances tested were not capable of interfering within 10 times the possible hypothetical plasma concentration reached in vivo with the function of the different reagents used in the study of complement. Five substances (Skin-ACGIH) have been studied for their effects on the complement system in vitro; four of them could be fully studied (allylic alcohol, cyclohexanone, phenol, dimethylacetamide). After this deep insight we can conclude that: 1. These substances are capable of interfering with the immune response through their complement activating capacity 2. These substances, throughout complement activation, can induce inflammation and reduction of important defensive functions that are complement mediated. 3. The results obtained encourage to study the complement system and especially CH50 in workers exposed to the selected substances in order to verify the possibility to enclose this test in the medical surveillance program.

[Determination of free and total S-phenylmercapturic acid in the biologic monitoring of exposure to benzene]

One of the biomarkers suggested by the ACGIH to assess the professional exposure to benzene is the S-phenylmercapturic acid in the end-shift urine. The existence in the urine of N-acetyl-S(1,2-dihydro-2hydroxypHenyl)-L-Cysteine, a precursor of SPMA that can be turned into it by acid hydrolysis, is a possible cause of miscorrelation between environmental and biological monitoring. The amount of measured SPMA depends on the degree of hydrolysis and therefore it is a function both of the urine PH and of the storage conditions of the sample. 40 urine samples have been collected from workers exposed to benzene, both smokers and not smokers, and for each sample the percentage of SPMA measurable at pH 2 and without pH correction (free SPMA) has been calculated with respect to the SPMA measured after quantitative hydrolysis, with the objectives to determine if a correct assessment of the exposure requires the determination of total SPMA and which concentration value could correspond to the BEI of 25 microg/g of creatinine established by the ACGIH. An aliquot of the urine samples has been treated with 9M H2SO4, a second one is brought to pH 2 and a third one is analyzed as it is. All samples are analyzed by HPLC/MS/MS in negative ions/MRM mode, and quantitative analysis is performed using the internal standard method. The percentage found in samples treated at pH 2 is on average 45% of the total SPMA for smokers and 60% for non smokers, while the free SPMA varies from 1% to 66% due to the urine pH variability and to the lower concentrations detected. The determination of total SPMA allows the standardization of the preanalyticalfactors and the dosage with analytical methods less sensitive than HPLC/MS/MS.

Comparison between external and internal standard calibration in the validation of an analytical method for 1-hydroxypyrene in human urine by high-performance liquid chromatography/tandem mass spectrometry

1-Hydroxypyrene is a metabolite of pyrene, a member of the class of polycyclic aromatic hydrocarbons (PAHs) whose toxic properties in some cases include carcinogenicity. The determination of 1-hydroxypyrene in human urine is used as a biological indicator for exposure to PAHs, which is related to the combustion of organic materials, like smoking, living in urban environments, and eating grilled or smoked food. The determination of 1-hydroxypyrene by high-performance liquid chromatography (HPLC) with fluorescence detection has very good sensitivity but it is not highly specific: this can reduce accuracy in the quantitative determination of low levels of analyte in a complex matrix like urine. An HPLC method that uses triple quadrupole mass detection has been validated with the objective both to improve the signal-to-noise (S/N) ratio and to achieve the maximum specificity for the analyte in those urine samples that are richer in possible inteferents. The calibration range for 1-hydroxypyrene is from 0.005-0.1 microg/L in the urine of non-smoking healthy volunteers. After solid-phase extraction, samples were analyzed by HPLC/tandem mass spectrometry (MS/MS) in the multiple reaction monitoring (MRM) mode. In order to obtain reliable results quantitative analysis must be performed by means of the internal standard method (we used deuterium-labelled 1-hydroxypyrene): the method accuracy is not less than 85%. The S/N ratio at a concentration of 0.1 microg/L is about 10, and therefore this can be considered the lowest limit of quantitation. The method performance does not change if urine samples are measured using a calibration curve prepared in methanol, thus reducing the time of analysis and costs.

Pesticides re-entry dermal exposure of workers in greenhouses

This research has the aim to evaluate the risk of pesticide dermal exposure for workers in greenhouses. We considered the following crops: tomato, cucumber and strawberry, largely spread in Bracciano lake district. The pesticides monitored were: tetradifon on strawberry: metalaxyl, azoxystrobin and fenarimol on cucumber; acrinathrin, azoxystrobin and chlorpyrifos ethyl on tomato. The dermal exposure was evaluated by Dislodgeable Foliar Residue (DFR) measurements employing transfer coefficients got from literature. For risk evaluation, we have compared the dermal exposures with Acceptable Operator Exposure Levels (AOEL). The re-entry time were obtained intercepting the dose decay curves with AOEL values. The re-entry times result higher than two days in the cases of chlorpyrifos on tomato (re-entry time: 3 days), azoxystrobin on tomato (4 days), and tetradifon on strawberry (8 days). The need of measuring specific transfer coefficients is pointed out.

High-performance liquid chromatographic determination of n-methylformamide, a biological index for occupational exposure to dimethylformamide

This report describes an analytical method for the biological monitoring of workers exposed to N,N-dimethylformamide (DMF), a solvent widely used in the chemical industry. The human main metabolites of DMF are N-hydroxymethyl-N-methylformamide (HMMF) and the minor metabolites N-methylformamide (NMF) and N-acetyl-S-(N-methylcarbamoyl)cysteine. The metabolite selected by the American Conference of Governmental Hygienists for occupational biomonitoring purposes, is NMF measured by gas chromatographic analysis, as during it HMMF may be converted to the minor metabolite NMF. HMMF and NFM can be measured independently using HPLC analysis. The procedure proposed here involves the thermal transformation of the primary metabolite HMMF into the minor metabolite NMF, which is then determined by HPLC. This method makes it possible to determine, using HPLC, both metabolites of DMF by measuring only one peak, thus offering two major advantages: (i) it increases the sensitivity of the test and (ii) it deploys only one reference standard.

[Criteria and methods for the study of occupational exposure to antineoplastic agents]

Risk assessment for occupational exposure to antiblastic chemotherapeutic drugs (ACD) is carried out by means of environmental and biological monitoring. These practices are not widespread and furthermore their results are frequently difficult to interpret. This paper discusses some of the most important aspects of risk assessment for ACD and in particular for their exposure evaluation. The following guidelines are proposed: a) working rooms, working procedures, type and quantity of drugs, and preventive measures must be checked using a standardized scheme for collecting data: an example of a check list experimented in some Italian hospitals is presented; b) cyclophosphamide, 5-fluorouracil, and Pt coordination compounds have been identified as tracers of drug mixtures usually administered, and their determination is recommended both in environmental and biological samples; c) for a correct evaluation of exposure, ACD should be determined firstly on the contaminated surfaces or on work clothes and secondly in urine of workers; the measurement of ACD in air must be limited to well documented conditions of high exposure and the urinary mutagenicity tests should be avoided; d) the biological monitoring practices should be enhanced, in particular the determination of ACD adducts to proteins and nucleic acids as promising indicators of effective dose.