The 2005 World Health Organization Reevaluation of Human and Mammalian Toxic Equivalency Factors for Dioxins and Dioxin-Like Compounds

In June 2005, a World Health Organization (WHO)-International Programme on Chemical Safety expert meeting was held in Geneva during which the toxic equivalency factors (TEFs) for dioxin-like compounds, including some polychlorinated biphenyls (PCBs), were reevaluated. For this reevaluation process, the refined TEF database recently published by Haws et al. (2006, Toxicol. Sci. 89, 4-30) was used as a starting point. Decisions about a TEF value were made based on a combination of unweighted relative effect potency (REP) distributions from this database, expert judgment, and point estimates. Previous TEFs were assigned in increments of 0.01, 0.05, 0.1, etc., but for this reevaluation, it was decided to use half order of magnitude increments on a logarithmic scale of 0.03, 0.1, 0.3, etc. Changes were decided by the expert panel for 2,3,4,7,8-pentachlorodibenzofuran (PeCDF) (TEF = 0.3), 1,2,3,7,8-pentachlorodibenzofuran (PeCDF) (TEF = 0.03), octachlorodibenzo-p-dioxin and octachlorodibenzofuran (TEFs = 0.0003), 3,4,4′,5-tetrachlorbiphenyl (PCB 81) (TEF = 0.0003), 3,3′,4,4′,5,5′-hexachlorobiphenyl (PCB 169) (TEF = 0.03), and a single TEF value (0.00003) for all relevant mono-ortho-substituted PCBs. Additivity, an important prerequisite of the TEF concept was again confirmed by results from recent in vivo mixture studies. Some experimental evidence shows that non-dioxin-like aryl hydrocarbon receptor agonists/antagonists are able to impact the overall toxic potency of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds, and this needs to be investigated further. Certain individual and groups of compounds were identified for possible future inclusion in the TEF concept, including 3,4,4′-TCB (PCB 37), polybrominated dibenzo-p-dioxins and dibenzofurans, mixed polyhalogenated dibenzo-p-dioxins and dibenzofurans, polyhalogenated naphthalenes, and polybrominated biphenyls. Concern was expressed about direct application of the TEF/total toxic equivalency (TEQ) approach to abiotic matrices, such as soil, sediment, etc., for direct application in human risk assessment. This is problematic as the present TEF scheme and TEQ methodology are primarily intended for estimating exposure and risks via oral ingestion (e.g., by dietary intake). A number of future approaches to determine alternative or additional TEFs were also identified. These included the use of a probabilistic methodology to determine TEFs that better describe the associated levels of uncertainty and "systemic” TEFs for blood and adipose tissue and TEQ for body burde

Prevalencia de sífilis y características del comportamiento de los jóvenes indígenas del Paraguay, 2016

El objetivo fue determinar la prevalencia de sífilis y características de comportamiento de los jóvenes indígenas del Paraguay en el 2016. Se realizó un estudio observacional, descriptivo de corte transversal con muestro probabilístico estratificado bietapico, que incluyó a jóvenes indígenas de 15 a 18 años de cinco familias lingüísticas de Paraguay. Se utilizó un cuestionario estructurado y para el tamizaje de sífilis se utilizó una test rápido treponémico y para confirmar los resultados reactivos se realizó VDRL, considerando como resultado positivo si el test rápido era positivo + VDRL positivo a una dilución de 1:4 o mayor y si la VDRL era menor a 1:4 con TPHA positivo. Los resultados se expresan como medidas de tendencia central, dispersión y proporciones. Ingresaron al estudio 546 jóvenes de 15 a 18 años, el 67,03% era del sexo femenino. Se identificaron 36 casos de sífilis, que representa una prevalencia de 6,6% [IC95%: 4,7-9,0]. Mayor prevalencia de sífilis se observó en los jóvenes que consumieron alcohol en la última relación sexual 20,6% (14/68) (p<0,001), sexo transaccional 40% (2/5) (p=0,010) y no utilización de condón 20,6% (14/68) (p<0,001). Se encontró una alta prevalencia de sífilis en la población juvenil indígena, relacionada al consumo de alcohol en la última relación, práctica de sexo transaccional y no utilización de preservativos. Se recomienda la implementación de estrategias específicas con abordaje intercultural apropiadas para una población joven, orientadas a disminuir las prácticas de riesgo y promocionar la utilización de preservativos

The 2005 World Health Organization reevaluation of human and mammalian toxic equivalency factors for dioxins and dioxin-like compounds

In June 2005 a WHO-IPCS expert meeting was held in Geneva during which the toxic equivalency factors (TEFs) for dioxin like compounds, including some polychlorinated biphenyls (PCBs), were re-evaluated. For this re-evaluation process the refined TEF database recently published by Haws and coworkers (Toxicol. Sci. 2006, 89:4-30) was used as a starting point. Decisions about a TEF value were made based on a combination of unweighted relative effect potency (REP) distributions from this database, expert judgement and point estimates. Previous TEFs were assigned in increments of 0.01, 0.05, 0.1, etc., but for this re-evaluation it was decided to use half order of magnitude increments on a logarithmic scale of 0.03, 0.1, 0.3 etc. Changes were decided by the expert panel for 2,3,4,7,8-pentachlorodibenzofuran (PeCDF) (TEF=0.3), 1,2,3,7,8-pentachlorodibenzofuran (PeCDF) (TEF=0.03), octachlorodibenzo-p-dioxin (OCDD) and octachlorodibenzofuran (OCDF) (TEFs=0.0003), 3,4,4’,5-tetrachlorbiphenyl (PCB 81) (TEF=0.0003), 3,3’,4,4’,5,5’-hexachlorobiphenyl (PCB 169) (TEF=0.03) and a single TEF value (0.00003) for all relevant mono-ortho substituted PCBs. Additivity, an important prerequisite of the TEF concept was again confirmed by results from recent in vivo mixture studies. Some experimental evidence shows that nondioxin-like aryl hydrocarbon receptor (AhR) agonists/antagonists are able to impact the overall toxic potency of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds and this needs to be investigated further. Certain individual and groups of compounds were identified for possible future inclusion in the TEF concept, including 3,4,4’-TCB (PCB 37), polybrominated dibenzo-p-dioxins (PBDDs) and dibenzofurans (PBDFs), mixed polyhalogenated dibenzo-p-dioxins and dibenzofurans, polyhalogenated naphthalenes and polybrominated biphenyls (PBBs). Concern was expressed about direct application of the TEF/TEQ approach to abiotic matrices such as soil, sediment etc., for direct application in human risk assessment. This is problematic, as the present TEF scheme and TEQ methodology is primarily intended for estimating exposure and risks via oral ingestion (e.g., by dietary intake). A number of future approaches to determine alternative or additional TEFs were also identified. These included the use of a probabilistic methodology to determine TEFs that better describe the associated levels of uncertainty and ‘systemic’ TEFs for blood and adipose tissue and total toxic equivalency (TEQ) for body burden