Quantification of Urinary Metabolites of Toluene and Xylene Isomers as Biological Indices of Occupational Exposure in Printing Industry Workers

Abstract

Background:In the printing industry, workers are occupationally exposed to an extensive variety of chemical solvents, including toluene and xylene. Biological monitoring is an essential tool for assessing occupational health risk. Objectives: The aim of the present study was to evaluate occupational exposure to toluene and xylene, as well as the biomarkers of exposure, in workers of the printing industry. Methods: The hippuric acid (HA) and o-, m-and p-methyl hippuric acids (o-, m-, p-MHAs) as the biomarkers of occupational exposure to toluene and each of the three xylene isomers, respectively, were determined in the urine samples of 84 subjects, including 44 printing workers and 40 non-exposed subjects. Results:The mean concentrations of toluene (37.64 ± 24.09 ppm) in the breathing zone of workers were higher, and the mean level of each of the three isomers of xylene (o-, m-, and p-xylene) was less than the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit values (TLVs). In addition, the levels of urinary HA, o-MHA, and m-and p-MHA in the exposed group were 0.15 ± 0.04, 0.11 ± 0.01, and 0.19 ± 0.07 g g -1 creatinine, respectively. Printing workers showed a significant increase in the levels of urinary HA compared to the non-exposed subjects (P < 0.001). The correlation analysis demonstrated significant correlations between the intensity of the occupational exposure to toluene and xylene and the level of exposure biomarkers in the urine. Conclusions: The results indicated that although all the urinary biomarkers of exposure were below the Biological Exposure Indices (BEIs) recommended by ACGIH, the levels of the urinary metabolites of toluene and xylene were increased in printing workers. Therefore, monitoring of occupational exposure to toluene and xylene is helpful in the following-up of affected workers in the printing industry.

Evaluation of Blood Lead Levels and Their Effects on Hematological Parameters and Renal Function in Iranian Lead Mine Workers

“…Lead generally inhibits the delta-aminolevulinic acid dehydratase activity, which enhances ALA in blood plasma and urine, and it is considered the most sensitive biomarker for the adverse effects of lead exposure. It should be noted that heme biosynthesis in the human body is not decreased until ALAD activity is largely inhibited (8,14). On the other hand, a significant rise in ZPP in the exposed group indicated the disturbance in the final step of heme biosynthesis.…”

“…Acute exposure to lead (PbB levels ≥ 50 µg/dL) quickly affects red blood cells and decreases their counts shortly after exposure due to the inhibition of ALAD activity. However, the heme-biosynthesis does not decrease until the activity of ALAD is inhibited by 80 -90% (8).…”

“…In Press(In Press):e95917. eases and PbB levels, but some of the relationships have not posed this association (8,14,(22)(23)(24)(25)(26)(27). Therefore, in the present matched case-control study, the occupational and biological exposures to lead were assessed to examine the association of occupational PbB levels with hematological parameters and kidney function in mine workers.…”

“…Lead toxicity has been reported in different biological systems and functions (7). Overexposure to lead is associated with anemia, high blood pressure, impotence, infertility, and reduced sexual performance, as well as damage to the kidneys and nervous system (8). The carcinogenic effects of lead on humans are unknown, but the International Agency for Research on Cancer (IARC) has classified lead and inorganic lead compounds in Group 2B (as possible human carcinogens) (9).…”

Personal NO2 and Volatile Organic Compounds Exposure Levels are Associated with Markers of Cardiovascular Risk in Women in the Cape Town Region of South Africa

“…3+4MHA appeared to be a prominent urinary metabolite/tracer for exposure in our study as it strongly correlated with all personal exposure levels (Table A1). 3+4MHA is a urinary marker for toluene (80% inhaled toluene metabolized to BMA or MHA) and the primary metabolite for xylene exposure (95% inhaled xylene metabolized to MHA post-exposure) [38,67,68,69,70]. Aside from being a diesel exhaust derivative, xylene is also often used as a solvent in industrial and household products (e.g., adhesives, coatings, degreasers, detergents, dyes, ink, paint, pesticides, polishes, and solvents) [18,56,57,58,59].…”