Pathology reevaluation of the Kociba et al. (1978) bioassay of 2,3,7,8-TCDD: implications for risk assessment

Advances in pediatric anesthesia services over the past 10 years in French-speaking sub-Saharan Africa

INTRODUCTION

To improve and maintain quality and safety in anesthesia, standards have been proposed regarding human resources, facilities and equipment, medications and intravenous fluids, monitoring, and the conduct of anesthesia. Compliance with these standards remains a challenge in French-speaking sub-Saharan Africa (SSA) and results in high morbidity and mortality particularly in children. This aim of this study was to assess the progress made in improving the pediatric anesthesia infrastructures, human resources, education, medications, and equipment in French-speaking SSA over the past 10 years (2013-2022).

METHODS

This is a descriptive, multicenter, cross-sectional study with retrospective data collection, conducted from September 1 to November 5, 2023. Comparative data from 2012 to 2022 were collected through an online survey. Descriptive statistics were used to summarize data.

RESULTS

Data were obtained from 12 countries out of 14. The number of hospitals providing pediatric surgery and anesthesia rose from 94 in 2012 to 142 in 2022 (+51%). The total number of physician anesthesiologists rose from 293 (0.1 physician anesthesiologists/100 000 inhabitants) in 2012 to 597 (0.2 physician anesthesiologists/100 000 inhabitants) in 2022 (+103.7%). Five (0.006 physician anesthesiologists/100 000 children) had completed a fellowship in pediatric anesthesia and intensive care in 2012, and 15 (0.01 physician anesthesiologists/100 000 children) in 2022 (+200%). Five physician anesthesiologists had an exclusive pediatric anesthesia practice in 2012, whereas they were 32 in 2022 (+540%). There is no specialized training in pediatric anesthesia and intensive care in any of these countries. Halothane was always available in 81.5% of the hospitals in 2012, and in 50.4% of the hospitals in 2022. Sevoflurane was always available in 5% of the hospitals in 2012, and in 36.2% in 2022. Morphine was always available in 32.2% in 2012, whereas it was available in 52.9% of them in 2022. Pediatric pulse oximeter sensors were available in 36% of the hospitals in 2012, and in 63.4% in 2022. Capnography was available in 5.3% of the hospitals in 2012, and in 48% in 2022.

CONCLUSION

Progress have been made over the last 10 years in French-speaking SSA to improve infrastructures, human resources, education, medications, and equipment for pediatric anesthesia in French-speaking SSA. However, major efforts must be continued. Standards adapted to the local context should be formulated.

Assessment of human health risks posed by consumption of fish from the Lower Passaic River, New Jersey

The Lower Passaic River (LPR) in New Jersey has been impacted by variety of human activities over the course of the last two centuries. In this risk assessment, we assessed potential human health risks associated with consumption of fish from the LPR, the human exposure pathway of greatest concern when addressing contaminated sediments. Our risk assessment incorporates fish consumption information gathered during a year-long, intercept-style creel angler survey and representative fish tissue concentrations for 156 chemicals of potential concern (COPCs) obtained from USEPA's public database (OurPassaic website: http://www.ourpassaic.org/projectsites/premis_public/index.cfm?fuseaction=contaminants). Due to the large number of COPCs investigated, this risk assessment was divided into two phases: (1) identification of COPCs that contribute to the majority of overall excess cancer risk and hazard estimates using deterministic and probabilistic methods, and (2) probabilistic characterization of risk using distributions of chemical concentration and cooking loss for those compounds identified in Phase 1. Phase 1 relied on point estimates of COPC concentrations and demonstrated that PCDD/Fs and PCBs (dioxin-like and non-dioxin-like) are the greatest contributors to cancer risk, while non-dioxin-like PCBs are the primary contributors to non-cancer hazard estimates. Total excess cancer risks for adult and child and receptors estimated in Phase 1 were within USEPA's acceptable excess cancer risk range, with the exception of RME child (3.0 x 10(-4) and 1.3 x 10(-4) for deterministic and probabilistic approaches, respectively). Phase 2 focused on PCDD, PCDF, and PCBs and used distributions of chemical concentrations in fish. The results showed that all excess cancer risk estimates were within the acceptable risk range, although non-cancer hazard estimates for PCBs slightly exceeded a Hazard Index of 1. This HHRA of LPR fish ingestion represents the most comprehensive evaluation conducted to date, and demonstrates that measured concentrations of COPCs are not likely to pose a health risk to people who currently consume fish from the LPR.

The acute lethality and endocrine effect of 1,2,3,7,8-PeCDD in juvenile goldfish (Carassius auratus) in vivo

1,2,3,7,8-PeCDD was administrated to juvenile goldfish (Carassius auratus) by peritoneal injections to explore the acute lethality and endocrine effects of 1,2,3,7,8-PeCDD in vivo. The value of acute median lethal dosage (LD50) of 1,2,3,7,8-PeCDD was determined in acute lethality tests. The endocrine effect of 1,2,3,7,8-PeCDD, whose exposed concentrations were determined based on the LD50 (1.84 mg/kg), was studied by measuring the plasma vitellogenin (Vtg) content in juvenile male goldfish with enzyme-linked immunosorbent assays (ELISA). Due to its significant induction of the plasma Vtg after one week's exposure in vivo in the 1/2 LD50 and LD30 groups, 1,2,3,7,8-PeCDD might be one of the important contributors to the estrogenic effect of PCDDs in the environment. The values of 1/2 LD50 and LD30 were within the range of the effective dosages of 1,2,3,7,8-PeCDD, indicating that there was a certain relationship between the estrogenic effective dosages and the LD50.

Nutritional hormesis

OBJECTIVE

Hormesis, the biological and toxicological concept that small quantities have opposite effects from large quantities, is reviewed with emphasis on its relevance to nutrition.

RESULTS

Hormetic and other dose-response relationships are categorized, depicted, and discussed. Evidence for nutritional hormesis is presented for essential vitamin and mineral nutrients, dietary restriction, alcohol (ethanol), natural dietary and some synthetic pesticides, some herbicides, and acrylamide. Some of the different hormetic mechanisms that have been proposed are reviewed.

CONCLUSIONS

The credence and relevance of hormesis to nutrition are considered to be established. The roles of hormesis in nutritional research and in formulating nutritional guidelines are discussed.

SPONSORSHIP

The New York City Department of Health and Mental Hygiene.

Identifying soil cleanup criteria for dioxins in urban residential soils: how have 20 years of research and risk assessment experience affected the analysis?

This article reviews the scientific evidence and methodologies that have been used to assess the risks posed by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and presents a probabilistic analysis for identifying virtually safe concentrations of TCDD toxicity equivalents (TEQ) in residential soils. Updated data distributions that consider state-of-the-science cancer and noncancer toxicity criteria, child soil ingestion and dermal uptake, bioavailability in soil, and residential exposure duration are incorporated. The probabilistic analysis shows that the most sensitive determinants of dose and risk are childhood soil ingestion, exposure duration, and the selected TCDD cancer potency factor. It also shows that the cancer risk at 1 per 100,000 predicted more conservative (lower) soil criteria values than did the noncancer hazard (e.g., developmental and reproductive effects). In this analysis, acceptable or tolerable soil dioxin concentrations (TCDD TEQ) ranged from 0.4 to 5.5 ppb at the 95th percentile for cancer potency factors from 9600 to 156,000 (mg/kg/d)(-1) with site-specific adjustments not included. Various possible soil guidelines based on cancer and noncancer risks are presented and discussed. In the main, the current toxicology, epidemiology, and exposure assessment data indicate that the historical 1 ppb TEQ soil guidance value remains a reasonable screening value for most residential sites. This analysis provides risk managers with a thorough and transparent methodology, as well as a comprehensive information base, for making informed decisions about selecting soil cleanup values for PCDD/Fs in urban residential settings.

An updated evaluation of the carcinogenic potential of 1,4-dioxane

This paper presents a critical review of the information pertaining to the potential carcinogenicity of 1,4-dioxane. The primary target organs for cancer via the oral route are the liver and the nasal cavity, however, the relevance of nasal cavity tumors to human exposures has been questioned. Liver tumors were accompanied by degenerative changes and appear only to occur at high doses where clearance mechanisms are saturated and liver toxicity is significant. Genetic toxicity data suggests that 1,4-dioxane is a very weak genotoxin. An increase in hepatocyte cell proliferation was reported and 1,4-dioxane was shown to act as a tumor promoter in rat liver and mouse skin carcinogenicity assays. Two reports are available from the literature regarding physiologically based pharmacokinetic (PBPK) modeling approaches to assess the risk of liver cancer for 1,4-dioxane. A comparison of cancer risk estimates from linear and nonlinear models in the presence or absence of PBPK modeling suggests that USEPAs current cancer slope factor significantly overestimates the potential cancer risk from 1,4-dioxane. This critical review of the scientific literature indicates that a formal reevaluation of the carcinogenic potency of 1,4-dioxane is warranted.

Balancing risks in the management of contaminated first nations fisheries

In the 1980s and 1990s, the Government of Canada closed and/or issued advisories for a number of shellfish fisheries in coastal areas of British Columbia because of dioxin contamination. Only the direct health risks (i.e., cancer) of consuming contaminated shellfish for the general population were considered by the Government in the formulation of risk management options. A focus on the direct risks does not provide an adequate basis for risk decisions as the countervailing risks which may be created from management measures may easily be overlooked. This study describes the potential health impacts of risk management options for aboriginal coastal peoples in the management of dioxin contamination. Gold River and Powell River in British Columbia, Canada, are the areas of focus. The cancer risks of consuming dioxin contaminated shellfish for these sites are estimated. To assess the countervailing risks of management decisions for comparison, a scenario was developed in which First Nations peoples substitute shellfish with store-bought foods in their diets in the event of a fishery closure or advisory. Increases in mortality due to coronary heart disease are estimated. The results suggest that the health risks of dietary changes among aboriginal peoples may be as significant as those related to eating dioxin contaminated shellfish.

Preliminary assessment of PCB risks to human and ecological health in the lower Passaic River

Concentrations of Aroclor mixtures and specific polychlorinated biphenyl (PCB) congeners were measured in surface sediments and aquatic biota (striped bass fillet, mummichog, and blue crab muscle and hepatopancreas) collected from the lower Passaic River. Several of the 47 surface sediment samples contained Aroclor concentrations that exceeded a National Oceanic and Atmospheric Administration (NOAA) benchmark level for "total PCBs" (22.7 micrograms/kg). Each of the 18 PCB congeners analyzed in aquatic biota was detected in one or more tissue samples, and numerous congeners were detected in every sample (IUPAC numbers 77, 105, 114, 118, 123, 126, 156, 157, 167, and 189). PCB congener concentrations were similar to those that have been reported in fish from other waterways that contain elevated levels of PCBs. Congener 118 was present at the highest concentration in almost all samples, and constituted 14-60% of the total PCB mass (sum of all congener masses) measured in any given tissue sample. In spite of the prevalence of PCB congeners in biota tissues (up to 1314 micrograms/kg total PCBs), Aroclors were not detected in bass or crab samples at a limit of detection of 33-55 micrograms/kg. This anomaly may be due to selective degradation of certain PCB congeners that are used to analytically recognize and quantitate Aroclors. Using the measured sediment concentrations, a food web model accurately predicted blue crab muscle concentrations of individual PCB congeners (typically within a factor of two) and was also fairly accurate for mummichog (typically within an order of magnitude). Concentrations in striped bass fillet were underestimated by factors of approximately 20-140. Increased cancer risk estimates associated with fish and crab consumption were obtained using four different methods. Using Aroclor tissue concentrations (one-half the limit of detection) and an Aroclor slope factor, total risks were 2.6 x 10(-6); using the "total PCB" measurements and an Aroclor slope factor, total risks were 1.9 x 10(-5); the "PCB-TEQ" method yielded total risks of 6.5 x 10(-4); and USEPA's recent suggested approach for evaluating "dioxin-like" and non-"dioxin-like" effects resulted in a total risk of 6.6 x 10(-4). This wide range in risk estimates indicates that it is critical to the risk management decision-making process that data requirements and risk assessment objectives be carefully evaluated early in the investigation process.

Reassessment of the carcinogenicity of polychlorinated biphenyls (PCBS)

The current policy for regulating polychlorinated biphenyls (PCBs) is based on one chronic bioassay that examined the carcinogenicity of a 60% chlorinated PCB (Norback & Weltman, 1985). All studies originally considered by the U.S. Environmental Protection Agency (EPA) for use in calculating a cancer slope factor (CSF) for PCBs were reevaluated and new CSFs calculated based on the results of a pathology reassessment (Moore et al., 1994). When studies of 60% chlorine PCBs from 3 different laboratories were compared, there was no scientific basis for selecting only 1 data set for deriving CSF estimates. Using a geometric mean to calculate a CSF based on all studies of PCBs with 60% chlorine replaces the current value of 7.7 (mg/kg/d)(-1) with a value of 1.9 (mg/kg/d)(-1). CSFs for PCBs containing less than 60% chlorine (54% and 42%) were less than 1.0 (mg/kg/d)(-1). Using a toxic equivalency factor (TEF) approach similar to that of 2,3,7,8-tetrachlorodibenzo-p-dioxin shows no correlation between toxic equivalent dose and CSFs, indicating that use of TEFs is not predictive of cancer potency for PCBs. Based on these findings, PCB cancer risk assessment policy would more closely reflect scientific data if (1) separate risk assessments were developed for each major PCB formulation and (2) all appropriate data were used when calculating cancer potency for PCB mixtures of 60% chlorine.

Selected lesions of dioxin in laboratory rodents

Dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin) has been the subject of intensive investigations in laboratory animals during the last 2 decades. Toxicity studies have been conducted in several species of rodents and include several carcinogenicity studies as well as numerous mechanistic studies initiated to elucidate dioxin's mode of action, as both a carcinogen and a toxicant. Hepatotoxicity is a primary effect of dioxin. There has been an increase in hepatocellular tumors reported in both rats and mice exposed to dioxin. In addition to neoplastic changes, dioxin causes a spectrum of toxic changes in the liver. Additional neoplastic changes include subcutaneous fibrosarcomas and thyroid follicular cell tumors in both rats and mice and histiocytic sarcomas in mice. Dioxin causes developmental effects in the palate and kidney of mice. Changes in the female reproductive tract include ovarian atrophy, sertoliform hyperplasia, and Sertoli cell tumors. Dosing in utero results in gross malformations of the external genetalia. The effects of dioxin on the rodent model of endometriosis are described. In males, there are lowered sperm counts in the epididymis and minor testicular effects following gestational administration of dioxin. Both estrogenic and antiestrogenic-like effects have been ascribed to dioxin in laboratory animals; these activities are the result of dioxin-specific pathways resulting in the same end points as classic reproductive toxicants.

Tumor-promoting effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin and phenobarbital in initiated weanling Sprague-Dawley rats: a quantitative, phenotypic, and ras p21 protein study

In an initiation-promotion protocol, female weanling Sprague-Dawley rats were initiated with 10 mg/kg nitrosodiethylamine and promotion was started after 30 days. Promotion regimens were as follows: 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD; 150 ppt in diet) continuously until day 450; phenobarbital (PB; 500 ppm in diet) until day 170; PB until day 170, followed by TCDD until day 240; and PB until day 170, followed by a basal diet (BD) until day 240 and subsequently TCDD from days 240 to 450. TCDD fed to initiated rats had a promoting effect on the development of adenosine triphosphatase-negative altered hepatocellular foci (AHF). At 450 days, the volume fraction of liver occupied by AHF was increased in initiated rats given TCDD continuously and in those given PB followed by TCDD, whereas the mean volume of AHF was significantly larger in initiated rats given TCDD continuously. PB and TCDD promoted similar phenotypes of AHF as seen in hemotoxylin and eosin-stained sections, but the eosinophilic phenotype most closely correlated with the development of hepatocellular neoplasms. The protooncogene product ras p21 protein was present in the majority of PB- and TCDD-promoted AHF, hepatocellular adenomas, and hepatocellular carcinomas. Eosinophilic AHF and ras p21 protein expression most closely correlated with neoplastic development, suggesting that these cell populations, when promoted, may be at greater risks for developing into neoplasms.

Assessment of dioxin-related health risks for the Melbourne metropolitan area

A community health risk assessment was conducted during 1990 in Melbourne for polychlorinated dibenzo-para-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) released in Laverton North by Nufarm Limited, an agricultural chemicals manufacturer. This risk assessment incorporated current scientific knowledge into hazard identification, dose-response assessment, exposure assessment and risk characterisation sections, according to the four-step framework used by the United States Environmental Protection Agency. The hazard identification showed that health effects are unlikely to result from general population exposures to PCDDs and PCDFs. The dose-response assessment supported a safety-factor approach for PCDD and PCDF risk assessment. The exposure assessment incorporated exaggerated assumptions to estimate both total daily exposure (203 pg total toxic equivalents of PCDDs and PCDFs, or 2.9 pg/kg body weight) and daily exposure attributable to Nufarm (56.4 pg, or 0.80 pg/kg body weight) under a worst-case scenario. The risk characterisation section found that exposures under 20 pg/kg body weight per day should not induce the aryl hydrocarbon hydroxylase system, which appears to be the starting point for PCDD and PCDF toxicity. We concluded that the general population exposure to PCDDs and PCDFs in Melbourne was within the range of acceptable daily intakes used by European and Canadian governments and the World Health Organization, as well as within the range of acceptable daily intakes derived using current scientific knowledge.

A proposed approach to regulating contaminated soil: identify safe concentrations for seven of the most frequently encountered exposure scenarios

Since 1980, more than 10,000 sites in the United States have been shown to contain soil which has elevated concentrations of various xenobiotics. Since that time, guidelines for deciding whether the level of contamination is worthy of concern have been proposed or promulgated by dozens of local, state, and federal regulatory agencies. Unfortunately, there has been little consistency in the guidelines suggested for each soil contaminant. For example, (a) the basis or rationale for some of the cleanup levels is unclear, (b) approaches to setting cleanup levels vary between states and agencies, (c) cleanup objectives often vary among agencies within the same state, and (d) the cleanup levels are usually set in a scientifically haphazard manner. This paper proposes that the most cost-effective and efficient way to quickly regulate contaminated soil is to establish "safe" concentrations for each chemical for the seven most common exposure scenarios. These exposure scenarios include (1) residential, (2) industrial, (3) agricultural, (4) recreational, (5) groundwater, (6) wildlife and aquatic species, and (7) runoff/erosion of particulates to waterways. The scientific approach and rationale for calculating the cleanup criteria are illustrated by evaluating dioxin and benzene, toluene, and xylene (BTX). The methods suggested here indicate that levels of dioxin of 25 and 50 ppb in residential and industrial soils, respectively, should be acceptable. The predominant concern for the agricultural and recreational scenarios is the runoff of particulates to waterways. For BTX, benzene will dictate the degree of cleanup and the primary hazard at most residential sites will be the inhalation of vapors. Benzene concentrations of 2.5, 14, and 250 ppm should be acceptable for residential, industrial, and recreational soils, respectively. Depending on the depth to groundwater and aquifer use, protection of groundwater may be the driving concern for establishing BTX cleanup levels and must be determined using site-specific factors.

Recent developments on the hazards posed by 2,3,7,8-tetrachlorodibenzo-p-dioxin in soil: implications for setting risk-based cleanup levels at residential and industrial sites

Since the publication of the Times Beach risk assessment in 1984, which suggested that residential soils were of concern when the level of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was in excess of 1 ppb, there has been continued interest in this topic. Studies conducted within the past 5 yr on the environmental and toxicological behavior of TCDD, as well as refinement of parameters regarding human exposure, indicate that previous assessments of the risk to humans posed by TCDD-contaminated soil were overestimated. In this paper, recent information drawn from nearly 100 recently published articles regarding the histopathology interpretation of the Kociba bioassay, environmental fate and half-life of TCDD in soil, and estimates of human exposure via soil ingestion, dermal contact, inhalation, surface runoff, and the consumption of fish were incorporated into a risk assessment. Cleanup levels for TCDD in residential and industrial soils were calculated based on most likely exposure scenarios. Probability distributions of key exposure parameters were incorporated into a Monte Carlo uncertainty analysis to predict the range and probability of TCDD uptake and corresponding cleanup levels in soil. This analysis demonstrated that the most significant route of human exposure to TCDD is through dermal contact with soil, followed by soil ingestion, fish consumption, and inhalation of airborne particulates. At residential sites, soils containing 20 parts per billion (ppb) of TCDD were found to pose a lifetime cancer risk no greater than 1 in 100,000 (10(-5) risk) under typical exposure conditions. Based on the Monte Carlo analysis, soil concentrations for the 75th and 95th percentile person were 12 and 7 ppb (10(-5) risk), respectively. In industrial soils, TCDD concentrations ranged between 131 and 582 ppb (10(-5) risk), depending on the amount of time spent outdoors under typical exposure conditions. Industrial soil concentrations of approximately 93 and 46 ppb (10(-5) risk) were calculated for the 75th and 95th percentile worker, respectively, engaged in outdoor activities. The range of TCDD concentrations in industrial soils was not reduced significantly when the consumption of fish from a neighboring waterway by off-site receptors was considered. While cleanup levels for TCDD should be derived on a site-specific basis, this analysis indicated that soil cleanup standards can be generally higher than those implemented over the past 8 yr.