Relative cancer potencies of selected dioxin-like compounds on a body-burden basis: comparison to current toxic equivalency factors (TEFs)

Relative Effect Potency Estimates for Dioxin-Like Compounds in Pregnant Women with Gestational Diabetes Mellitus and Blood Glucose Outcomes Based on a Nested Case-control Study

To improve the applicability of the toxic equivalents principle for human health risk assessment, systemic relative effect potencies (REPs) for dioxin-like compounds (DLCs) deriving from human in vivo data are required. A prospective nested case-control study was performed to determine REPs from the human serum concentration of DLCs using gestational diabetes mellitus (GDM) and fasting blood glucose (FBG) as the end points of concern. Serum concentration of 29 DLCs from 77 cases and 154 controls were measured. Logistic and linear regression were used to estimate the effects of individual congeners on GDM and FBG, respectively. The REPs based on GDM and FBG were calculated from the ratios of regression coefficients, β_i (DLCs)/β_TCDD. Two sets of consistent human serum-based REPs, that is, GDM-REP and FBG-REP, were established and largely agree with REPs from other human studies. These human-serum REPs show much smaller variation compared to the 4 to 5 orders of magnitude span in REPs database for the present WHO-TEF determination. Moreover, the established REPs fitted well with WHO-TEFs, especially for polychlorinated dibenzo- p-dioxins, furans. These REPs reflecting real human exposure scenarios exhibited validity and could be used to improve health risk assessment of human body burden of DLCs.

Biomonitoring-based environmental public health indicators

This chapter discusses the use ofbiomonitoring-based indicators of exposure to environmental pollutants in environmental health information systems. Matrices for biomonitoring, organization and standardization of surveillance programs, the use of intake and body burden data, and the interpretation of surveillance data are discussed. The concept of environmental public health indicators is demonstrated using the "Persistent organic pollutants in human milk" indicator implemented in the Environment and Health Information System (ENHIS) of the WHO Regional Office for Europe. This indicator is based on the data from the WHO-coordinated surveillance of persistent organic pollutants in human milk as well as data from selected national studies. The WHO survey data demonstrate a steady decline in breast milk concentrations of dioxins across Europe. The data from biomonitoring surveys in Sweden also show a steady decline of breast milk concentrations of most persistent organic pollutants since 1970s with the exception of polybrominated diphenyl ethers (PBDEs) which increased rapidly until the late 1990s and then started to decline after the implementation of policy measures aiming at reducing exposures. The application of human biomonitoring data in support of environmental public health policy actions requires carefully designed standardized and sustainable surveillance, comprehensive interpretation of the data, and an effective communication strategy based on credible information presented in the form of indicator factsheets.

Derivation of biomonitoring equivalent (BE) values for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds: a screening tool for interpretation of biomonitoring data in a risk assessment context

Recent efforts by the U.S. Centers for Disease Control and Prevention and other researchers have resulted in a growing database of measured concentrations of dioxins and related compounds in blood samples taken from the general population. However, few tools exist to assist in the interpretation of the measured values in a health risk context. Biomonitoring equivalent (BE) values are defined as the concentration or range of concentrations of a chemical or its metabolite in a biological medium (blood, urine, or other medium) that is consistent with an existing health-based exposure guideline, and are derived by integrating available data on pharmacokinetics with existing chemical risk assessments This study reviews available health based exposure guidance values for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds from a variety of agencies including the World Health Organization Joint Expert Committee on Food Additives (JECFA), the European Commission Scientific Committee on Foods (ECSCF), the United Kingdom Committee on Toxicology (UKCOT), and the U.S. Agency for Toxic Substances and Disease Registry (ATSDR) to estimate corresponding BE values for dioxin-like compounds in blood on a serum lipid-adjusted basis. Based on data from the animal studies underlying the exposure guidance values, a serum lipid-adjusted dioxin toxicity equivalent (TEQ) concentration of approximately 15 ppt is consistent with the ATSDR minimal risk level (MRL) for dioxins. Serum lipid-adjusted TEQ concentrations of approximately 31 to 74 ppt are consistent with the tolerable intakes estimated by the other three agencies. These values may be used as screening tools for evaluation of biomonitoring data for dioxins in the context of existing risk assessments and for prioritization of the potential need for additional risk assessment efforts for dioxins.

Characterization and biological effect of Buenos Aires urban air particles on mice lungs

Exposure to increased levels of ambient air particulate matter (PM) is associated with increased cardiopulmonary morbidity and mortality. Its association with adverse health effects and the still unclear mechanisms of action are of concern worldwide. Our objective was to analyze air PM from downtown Buenos Aires (UAP-BA), and evaluate its biological impact on normal airways. We studied the inflammatory response to intranasal instillation of UAP-BA in a short-term-exposure mouse model. We analyzed UAP-BA morphology by scanning electron microscopy and characterized particle chemical composition by energy dispersive X-ray analysis and capillary gas chromatography. We evaluated lung changes by histomorphometry and histochemical methods. Regarding size, surface area and distribution, UAP-BA proved to be small spherical ultrafine particles: free, in clusters and associated to a matrix. The particles contained polycyclic aromatic hydrocarbons, polychlorinated biphenyls and almost no metal traces. Histologically, UAP-BA induced the recruitment of phagocytes, a reduction in air spaces, an increase in mucous PAS positive cells and weak incomplete elastic fiber network. Our results demonstrate that UAP-BA causes adverse biological effects on the respiratory tract generating inflammation that, in turn, may cause tissue injury or organ dysfunction and may contribute to the pathogenesis of lung diseases.

TCDD exposure-response analysis and risk assessment

We examined the relation between cancer mortality and time-dependent cumulative exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) estimated from a concentration- and age-dependent kinetic model of elimination, and we estimated incremental cancer risks at age 75. Data from the National Institute for Occupational Safety and Health study of 3,538 workers with occupational exposure to TCDD were analyzed using standardized mortality ratios and Cox regression procedures. Analyses adjusted for potential confounding by age, year of birth, and race and considered exposure lag periods of 0, 10, or 15 years. Other potential confounders including smoking and other occupational exposures were evaluated indirectly. To explore the influence of extreme values of cumulative TCDD ppt-years, we restricted the analysis to observations with exposure below the 95th percentile or used logarithmic (ln) transformed exposure values. We applied penalized smoothing splines to examine variation in the exposure-response relation across the exposure range. TCDD was not statistically significantly associated with cancer mortality using the full data set, regardless of the lag period. When we restricted the analysis to observations with exposure below the 95th percentile, TCDD was associated positively with cancer mortality, particularly when a 15-year lag was applied (untransformed exposure data: regression coefficient , standard error (s.e.) = 1.4 x 10(-6), p < 0.05; ln-transformed exposure data: , s.e. = 2.9 x 10(-2), p < 0.05). The estimated incremental lifetime risk of mortality at age 75 from all cancers was about 6 to more than 10 times lower than previous estimates derived from this cohort using exposure models that did not consider the age and concentration dependence of TCDD elimination.