Estudo retrospectivo dos níveis de ácido hipúrico urinário em exames de toxicologia ocupacional / A retrospective study analysis of urinary hippuric acid levels in occupational toxicology exams

O ácido hipúrico é o principal metabólito do tolueno, solvente amplamente utilizado em processos industriais e com importantes efeitos tóxicos, fato que justifica a preocupação em monitorar regularmente sujeitos com risco de exposição ocupacional a este solvente. O objetivo deste trabalho foi avaliar os níveis de ácido hipúrico encontrados em trabalhadores submetidos à monitorização biológica. Foi realizado um estudo retrospectivo com dados dos anos de 2002 a 2005, no qual foram analisados os resultados e a situação do empregado na oportunidade do exame (periódico, demissional e admissional). Os resultados indicam uma redução significativa nos níveis de ácido hipúrico em 2005. Exames periódicos obtiveram resultados superiores aos exames admissionais e demissionais, e não foi verificada diferença significativa nas proporções dos sujeitos agrupados de acordo com a situação funcional em cada um dos intervalos estabelecidos segundo o valor de referência e o índice biológico máximo permitido. Os níveis de ácido hipúrico detectados indicam um baixo de risco de exposição ao tolueno na população avaliada, provavelmente em decorrência da preocupação crescente com a implantação de medidas de higiene ocupacional.

Hippuric acid is the primary metabolite of toluene, a solvent widely used in industrial processes with considerable toxic effects, a fact which justifies regularly monitoring individuals with occupational exposure to this solvent. This work aims at evaluating urinary hippuric acid levels found in workers subject to biological monitoring. A retrospective study was carried out with data referring from 2002 to 2005, in which exams results and employment status were analyzed (periodic, post-employment, and pre-employment exams). Results indicate a significant reduction in hippuric acid levels for 2005. Periodic exams presented higher results than pre-employment and post-employment exams. No significant difference was found in individuals grouped according to their status in each of the established intervals, their reference numbers, and maximum biological levels allowed. Hippuric acid levels detected indicate low risk of toluene exposure for the population under evaluation, probably due to a growing concern with the deployment of measures regarding occupational hygiene.

[Correlation between toluene environmental monitoring and biological index of urinary hippuric acid of workers in the coke industry]

Toluene is an organic solvent that it is one of the byproducts in the coke industry. Exposure to toluene causes central nervous system dysfunction and others disorders. Many workers are exposed to toluene due to leakage from tracks. Therefore the aim of this study was to determine the levels of exposure through environmental and biological monitoring of toluene Air toluene sampling of air inhaled by 36 coke oven workers was done by using activated charcoal tubes and personal sampling pumps. At the e[1id of the shift, urine samples of workers and control group were collected by urine samplers. Air toluene was determined by GC, urinary hippuric acid by FIPLC and urine creatinine level was determined by auto analyzer. The mean of air toluene and urinary hippuric acid levels in exposed and control samples were 14.34 ppm, 0.33 and 0.28 g/g creatinine. Air toluene and urinary hippuric acid showed a correlation of r = 0.8. Toluene TWA was lower than the TLV-TWA [p=0.000]. Urinary hippuric acid concentration was also lower than the BEI [p=0.008]. Difference between exposed and unexposed group was not significant. This study showed that hippuric acid because of its interaction with background factors can not be used as a sensitive biomarker for biomonitoring

Criterios para la vigilancia biológica en la exposición laboral al tolueno / Criteria for surveillance of work-related exposure to toluene

Se detectaron en los exámenes periódicos del personal con riesgo de exposición a tolueno, valores alterados en su estudio específico de control biológico (ácido hipúrico en orina), sin correlato clínico. El objetivo de este estudio fue revisar los datos disponibles relacionados con la seguridad y eficacia del rastreo de ácido hipúrico en orina como control y determinar el estado actual de la población en estudio, respecto de si se encuentra o no expuesta al tolueno, mediante rastreos que testifiquen datos más confiables. Se partió de la hipótesis de que el ácido hipúrico en orina es un examen de baja especificidad e influenciado por múltiples factores confundidores, lo cual implica una tasa de falsos positivos alta. Para aumentar la especificidad, se agregó otro test de control de exposición al tolueno consistente en la determinación de ortocresol en orina. Posteriormente se compararon los niveles de ácido hipúrico y ortocresol en 35 trabajadores expuestos y 5 no expuestos. En los primeros, 12 (12/35) presentaron ácido hipúrico sobre la norma, en tanto los segundos mostraron uno (1/5) alterado. El ortocresol resultó normal en todos los sujetos estudiados. Los niveles de exposición estuvieron bajo la norma en todos ellos. El estudio confirmaría la baja especificidad del ácido hipúrico como control de exposición, lo que implica una tasa alta de falsos positivos. El análisis de ortocresol es, en principio, más preciso y exacto. Aunque desconocemos la especificidad del mismo medida en poblaciones de tamaño suficiente, sería más sensible para detectar expuestos. La suma de ambos aumentaría la especificidad total y disminuiría la tasa de falsos positivos. Se propone, en consecuencia, un nuevo programa de vigilancia biológica.

Effects of Air Pollutants on Childhood Asthma

Epidemiologic studies have suggested the association between environmental exposure to volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) and the increased risk of incurring asthma. Yet there is little data regarding the relationship between personal exposure to air pollution and the incidence of asthma in children. This study was designed to evaluate the effect of exposure to air pollution on children with asthma by using exposure biomarkers. We assessed the exposure level to VOCs by measuring urinary concentrations of hippuric acid and muconic acid, and PAHs by 1-OH pyrene and 2-naphthol in 30 children with asthma and 30 children without asthma (control). The mean level of hippuric acid was 0.158+/-0.169micromol/mol creatinine in the asthma group and 0.148+/-0.249micromol/mol creatinine in the control group, with no statistical significance noted (p=0.30). The mean concentration of muconic acid was higher in the asthma group than in the control group (7.630+/-8.915micromol/mol creatinine vs. 3.390+/-4.526micromol/mol creatinine p=0.01). The mean level of urinary 1-OHP was higher in the asthma group (0.430+/-0.343micromol/mol creatinine) than the control group (0.239+/-0.175micromol/mol creatinine), which was statistically significant (p=0.03). There was no difference in the mean concentration of 2-NAP between the two groups (9.864+/-10.037micromol/mol in the asthma group vs. 9.157+/-9.640micromol/mol in the control group, p=0.96). In conclusion, this study suggests that VOCs and PAHs have some role in asthma.

High levels of hippuric acid in the urine of Thai press workers.

Toluene is an important toxic volatile agent found in many modern industrial processes. Toluene exposure is of particular concern because of the ongoing exposure of thousands of workers in industrial plants and recent research has indicated that toluene/exposure can result in chronic toxicity. The monitoring and control of toluene exposure among at-risk workers is necessary. Urine hippuric acid determination is a helpful test monitoring groups of at-risk workers. In this study, urine samples were obtained from 20 control subjects and 48 press workers from a factory in Bangkok. Each subject gave a specimen of urine; each specimen was analyzed for hippuric acid level by the Ohmori method. The average urine hippuric acid level in the control group was 0.23 +/- 0.15 mg/gCr (range = 0.05 - 0.58 mg/gCr) while that of the experimental group was 0.37 +/- 0.37 mg/gCr (range = 0.06 - 0.18 mg/gCr). A significant higher urine hippuric acid level among the press workers was found (p = 0.03). Based on this study, the prevention of exposure to toluene among high-risk workers is recommended.

Occupational exposure to toluene inhalant among young car-paint-workers

Forty young car-paint-workers from Mahalla El Kobra, Gharbia Governorate were selected from those who recently joined work [less than one week] at car workshops and were subjected to the following: a] complete personal, family, and medical history taking, b] Complete medical examination, c] Psychological assessment battery of 24 items, d] Complete blood picture, liver function tests, blood urea, serum calcium, potassium, magnesium, and acid phosphatase, and hippuric acid level in urine. Results showed disturbed general behavior. Of the studied cases 89.7% suffered from irritability, 68.9% from talk slow, 34.5% from depressed mood, 65.5% had illusionary misinterpretations, 72.4% had visual hallucinations, 24.2% had distorted body form perception, and 55.2% showed impaired recent memory. Serum magnesium and Hippuric acid level in urine showed significant increase after three-month period of exposure. Attention is drawn to the necessity for educational programs in this area

Electrokinetic energy conversion by aqueous oxalic acid, citric acid, ascorbic acid, hippuric acid, and acetyl salicylic acid across urinary bladder membranes.

Efficiency of energy conversion for electro-osmosis and streaming potential and the degree of coupling of acids across urinary bladder membranes of goat have been computed using non-equilibrium thermodynamic theory. The energy conversion maxima and degree of coupling for acids responsible for the formation of urinary calculi are found to be much low as compared to urea and urine.

Benzoic acid metabolism in presence of Schistosoma mansoni infection in mice.

The metabolism of benzoic acid was examined in S. mansoni infected CBA mouse. The result showed that control animals dosed with 150 mg/kg benzoic acid resulted in urinary excretion of two metabolites, hippuric acid and benzoic acid glucuronide. Administration of the same dose to animal carrying S. mansoni for a period of over 6 weeks resulted in decreased formation of hippuric acid and total elimination of benzoic acid by glucuronide pathway.