Indicadores biológicos de exposição a solventes orgânicos e sua inter-relação com o estresse oxidativo

Abstract

The use of organic solvents in the work environment represents a significant risk to workers health. The painters composed, among others, a group of individuals who are in direct contact with solvents through the respiratory and dermal route. The biological monitoring, through biological exposure index (BEI) determination, can ensure the emergence of chronic occupational diseases, even in a long-term exposure. Thus, it was aimed to optimize and validate a methodology using high performance liquid chromatography with ultraviolet detector (HPLC-UV), for the simultaneous quantification of the following BEI: hippuric acid (HA), 3-methylhippuric acid (3mHA), mandelic acid (MA) and phenylglyoxylic acid (PGA) in urine to the solvents toluene, xylene, styrene (MA and PGA) and ethylbenzene (MA) respectively. In addition, there are reports that organic solvents, among other agents, cause imbalance in pro - and antioxidant defenses of the body, causing damage to the health of workers due to the oxidative stress. So, we quantified some blood biomarkers of oxidative stress, and its possible relationship to the levels of BEI in painters (n = 50) of an industry in Caxias do Sul, Brazil, and compared with non-exposed subjects. Thus, the biomarkers analyzed were: endogenous antioxidants such as reduced glutathione (GSH), the enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx); exogenous antioxidants such as vitamins C and E; in addition we determined two biomarkers of oxidation, in lipid peroxidation, we evaluate the levels of malondialdehyde (MDA) and in oxidation of proteins, we analysed protein carbonyl (PCO). The analytical parameters evaluated were linearity, accuracy, recovery and limits of detection (LOD) and quantification (LOQ). For all the analysed BEI, the linear regression coefficient > 0.99; CV% < 6 %; bias% < ± 10; recovery > 95%; LOD between 0.001 to 0.009 g.L-1 and LOQ between 0.04 to 0.02 g.L-1. In the application of the method, in exposed group (n=50), everyone had urinary concentration of HA; 2.5% of those were above the reference values (RV) and only 8% of these, had values above the biological exposure limit (BEL). Methylhippuric acid was found in 96%, PGA in 30%, and MA in 26% of the samples analyzed, those values, were all below the BEL. Among non-exposed ones, only urinary HA has been found, the values were 0.058 to 0.23 g / g creatinine. In relation to the oxidative stress biomarkers, the levels of plasma MDA and serum PCO were significantly increased compared to controls (p <0.01). The levels of erythrocyte GSH (p<0.05); blood SOD, CAT and GPx (p<0.001) were also significantly increased, showing an increase in antioxidant system in response to the deleterious effects of exposure to paints. The levels of exogenous antioxidants, such as vitamin C and vitamin E were significantly reduced in these subjects (p<0.05) compared to control. Moreover, it was observed a correlation between the biomarkers of oxidative stress and some BEI. The urinary mandelic acid, biological exposure index for styrene and ethylbenzene, showed a positive correlation with the enzymes SOD and CAT, and the MDA (p<0.01) and a negative correlation with vitamin E (p<0. 05). The hippuric acid found in urine samples showed a positive correlation with the blood levels of GPx (p<0.001). Furthermore, a positive correlation was found between MDA and PCO (p<0.001), and negative correlation between PCO with GPx, with vitamin C and with E (p <0.05). The results of the validation methodology showed linearity, precision and accuracy, allowing conclude that the method is reliable to quantify the biological exposure indices, HA, mHA, MA and PGA, simultaneously. Furthermore, the levels of these BEI showed to be within the biological exposure limits. The biomarkers of oxidative stress related to lipid peroxidation and the oxidation of proteins were significantly increased even with an increase in endogenous antioxidants analyzed, GSH, SOD, CAT and GPx. Moreover, there was a depletion of exogenous antioxidants, such as vitamins C and E. So with this work we can suggest that the biological exposure limit for the metabolites of toluene, xylene, styrene and ethylbenzene analyzed, failed to ensure the balance in antioxidant/oxidant status to exposed workers.