Association between urinary BTEX metabolites and dyslexic odds among school-aged children.

Benzene, toluene, ethylbenzene, and xylene (BTEX) are ubiquitous in the environment, and all of them can cause neurotoxicity. However, the association between BTEX exposure and dyslexia, a disorder with language network-related regions in left hemisphere affected, remains unclear. We aimed to assess the relationship between BTEX exposure and dyslexic odds among school-aged children. A case-control study, including 355 dyslexics and 390 controls from three cities in China, was conducted. Six BTEX metabolites were measured in their urine samples. Logistic regression model was used to explore the association between the BTEX metabolites and the dyslexic odds. Urinary trans,trans-muconic acid (MU: a metabolite of benzene) was significantly associated with an increased dyslexic odds [odds ratio (OR) = 1.23, 95% confidence interval (CI): 1.01, 1.50], and the adjusted OR of the dyslexic odds in the third tertile was 1.72 (95% CI: 1.06, 2.77) compared to that in the lowest tertile regarding urinary MU concentration. Furthermore, the association between urinary MU level and the dyslexic odds was more pronounced among children from low-income families based on stratified analyses. Urinary metabolite levels of toluene, ethylbenzene, and xylene were not found to be associated with the dyslexic odds. In summary, elevated MU concentrations may be associated with an increased dyslexic odds. We should take measures to reduce MU related exposure among children, particularly those with low family income.

Rapid determination of hippuric acid as an exposure biomarker of toluene using a colorimetric assay and comparison with high-performance liquid chromatography.

Occupational exposure to toluene is associated with health risks that require reliable monitoring methods. Hippuric acid (HA), a urinary metabolite of toluene, serves as a valuable biomarker for such exposure. Colorimetric methods for the quantitative determination of HA have gained prominence due to their simplicity, cost-effectiveness, and suitability for field application. In the present study, a simple colorimetric technique was optimized for the determination of HA in the urine sample, and compared with a usual HPLC technique. The central composite design (CCD) was applied to examine the effective parameters on the colorimetric determination of HA. The calibration curve for HA was established within the concentration range of 6 to 100 mg L-1 with R2 = 0.97. The detection limit (LOD) and quantification limit (LOQ) were determined to be 1.8 mg L-1 and 6 mg L-1 respectively. The relative standard deviation (RSD%) was less than 5%, and the recovery% (R%) was 90.5-100.1. The overall results showed good agreement between the colorimetric and HPLC results. There was a significant relationship between the results obtained from HPLC and colorimetric methods especially for higher concentration levels of HA (≥ 500 mg/g creatinine). In conclusion, our optimized colorimetric method is a simple, cost-effective, and rapid method for determination of HA in occupational exposure, which is comparable with the HPLC technique.

Niveles urinarios de ácido trans, trans mucónico y orto cresol en una población infanto-juvenil residente en Ciudad Autónoma de Buenos Aires y Conurbano Bonaerense / Urinary levels of trans, trans muconic and ortho cresol in an infant-juvenile population resident in the Autonomous City of Buenos Aires and the Conurbano of Buenos Aires

Introducción: la exposición crónica al benceno y tolueno produce alteraciones sobre la médula ósea y el sistema nervioso central, entre otros. En orina, el ácido trans, trans mucónico (t, t-MA) es uno de los biomarcadores de exposición al benceno y el o-cresol (oCre) al tolueno. Objetivo: analizar los resultados de los niveles de t, t-MA y oCre urinarios en una población infanto-juvenil residente en Ciudad Autónoma de Buenos Aires y Conurbano Bonaerense potencialmente expuesta a benceno y tolueno ambiental. Materiales y métodos: se realizó un estudio retrospectivo de los resultados de t, t-MA y oCre urinarios. Las muestras de orina ingresaron al laboratorio con solicitud de t, t-MA (n=1519) y oCre (n=1447) durante el período 2011-2017 (rango etario entre 0 a 19 años). El t, t-MA se cuantificó por UFLC con detector de arreglo de diodos y el oCre por CG con detector de ionización por llama. Resultados: la edad promedio de los pacientes fue de 4,8 años y la mediana 4,6 años.Las concentraciones de t, t-MA urinario fueron: menor de 50 μg/l (44,8%); entre 50-500 μg/l (52,1%) y mayores de 500 μg/l (3,1%). Expresadas por gramo de creatinina: entre 15-163 μg/g creatinina (60,4%) y mayores de 163 μg/g creatinina (39,6%). El límite de cuantificación de t, t-MA fue de 50 μg/l. Las concentraciones de oCre urinario fueron: menor de 0,20 mg/l (97,7%) y entre 0,20-0,50 mg/l (2,3%) y mayor de 0,50 mg/l (0%). Expresadas por gramo de creatinina: menor de 0,30 mg/g creatinina en el 0,8% y mayores de 0,30 mg/g creatinina en el 1,5%. El límite de cuantificación de oCre fue de 0,20 mg/l. Conclusiones: los resultados del trabajo podrían indicar una contaminación ambiental persistente, en especial en el Conurbano Bonaerense, donde debería continuarse el monitoreo de algunas zonas. Pero, por otro lado, es de vital importancia tener en cuenta los factores de confusión, tales como la dieta, la exposición al humo de tabaco ambiental (fumador pasivo) y la tasa de excreción renal que llevarían a una sobre-estimación de los resultados y a una incorrecta toma de decisiones.

Introduction: Chronic exposure to benzene and toluene produces alterations in the bone marrow and the central nervous system, among other effects. In urine, trans, trans muconic acid (t, t-MA) is one of the biomarkers of exposure to benzene and o-cresol (oCre), to toluene. Objective: To analyze the results of urinary t, t-MA and oCre levels in an infant-juvenile population resident in the Autonomous City of Buenos Aires and the Conurbano Bonaerense, potentially exposed to environmental benzene and toluene. Materials and methods: A retrospective study of urinary t, t-MA and oCre results was performed. The urine samples entered the laboratory with the request of t, t-MA (n = 1519) and oCre (n = 1447) during the period 2011- 2017. The age range of the population was between 0 and 19 years. The t, t-MA was quantified by UFLC with diode array detector and the oCre by GC with flame ionization detector. Results: The average age of the patients was 4.8 years and the median age was 4.6 years. The urinary concentrations of t, t-MA were: below 50 μg/l (44.8%); between 50-500 μg/l (52.1%) and above 500 μg/l (3.1%). Expressed per gram of creatinine: between 15-163 μg/g creatinine (60.4%) and greater 163 μg/g creatinine (39.6%). The limit of quantification of t, t-MA was 50 μg/l. The urinary oCre concentrations were: less than 0.20 mg/l (97.7%) and between 0.20-0.50 mg/l (2.3%). Expressed per gram of creatinine: less than 0.30 mg/g creatinine in 0.8% and greater than 0.30 mg/g creatinine in 1.5%. The limit of quantification of oCre was 0.20mg/l. Conclusions: The results of the study could indicate persistent environmental contamination, especially in the Conurbano Bonaerense, where monitoring of some areas should be continued. However, it is of vital importance to take into account the confounding factors, such as diet, exposure to environmental tobacco smoke (passive smoking) and the rate of renal excretion, which would lead to an over-estimation of the results and to incorrect decision-making.

Determinacao de orto-cresol urinario por cromatografia em fase gasosa utilizando-se detector de ionizacao de chama / Gas-chromatographic determination of orto-cresol in urine using flame ionization detector

O tolueno e um solvente aromatico com larga utilizacao industrial, sendo usado na fabricacao de varios produtos como cola, tiner, tintas e outras. Sua acao neurotoxica constitui-se no principal risco a saude dos trabalhadores, tornando-se indispensavel medidas de controle e avaliacao da exposicao ocupacional. A monitorizacao biologica do tolueno e realizada frequentemente, atraves da determinacao de seu principal produto de biotransformacao na urina, o acido hipurico, que esta tambem, presente em urina de individuos nao expostos ao solvente. Pequena fracao do tolueno absorvido e oxidado a compostos aromaticos incluindo o orto-cresol, o qual nao e encontrado significativamente, em urina de nao expostos. objetivando padronizar metodologia analitica para a determinacao deste metabolito em urina de individuos expostos e nao expostos ocupacionalmente ao tolueno, foi elaborado o presente trabalho. A tecnica selecionada foi a cromatografia em fase gasosa acoplada a detector de ionizacao de chama (CG/DIC). O metodo analitico apresentou boa precisao (CV intra e interensaio na faixa de 2,4 a 5,4 por cento) e recuperacao media de 98,0 por cento. O metodo apresentou linearidade na faixa de 0,2 a 3,0 micragrama/mL, sendo o limite de quantificacao o valor de 0,2 micragrama/ml

Valores de referência do ácido hipúrico urinário na regiäo metropolitana de Belo Horizonte / Urinary hippuric acid reference values in Belo Horizonte metropolitan area, Brazil

Objetivando estabelecer a faixa de valor referência para o ácido hipúrico na regiäo metropolitana de Belo Horizonte, urinas de indivíduos näo expostos ocupacionalmente ao tolueno foram analisadas por cromatografia em fase gasosa, utilizando-se detector de ionizaçäo de chama. Os valores encontrados experimentalmente (n=281) variaram de <0,1 a 2,79 g/L, mas a aplicaçäo de estudo estatístico delimita como faixa de referência,a nível de significância de 95 porcento, os valores de 0,361 a 0,481 g/L. Säo descritas, também, as condiçöes analíticas padronizadas para a determinaçäo cromatográfica do ácido hipúrico urinário