scholarly journals Estimating the no-observed-adverse-effect-level (NOAEL) of hormetic dose-response relationships in meta-data evaluations

MethodsX ◽  
2021 ◽  
pp. 101568
Author(s):  
Evgenios Agathokleous ◽  
Michael N Moore ◽  
Edward J Calabrese
Keyword(s):  
Adverse Effect ◽  
Dose Response ◽  
Meta Data ◽  
Adverse Effect Level ◽  
Effect Level

scholarly journals Estimation of Benchmark Dose of Cumulative Cadmium Exposure for Renal Tubular Effect

2021 ◽  
Vol 18 (10) ◽  
pp. 5177
Author(s):  
Kazuhiro Nogawa ◽  
Yasushi Suwazono ◽  
Yuuka Watanabe ◽  
Carl-Gustaf Elinder
Keyword(s):  
Adverse Effect ◽  
Least Squares ◽  
Dose Response ◽  
Cadmium Exposure ◽  
Benchmark Dose ◽  
Tubular Damage ◽  
Limit Values ◽  
Adverse Effect Level ◽  
Effect Level ◽  
Renal Tubular

Objectives: The aim of this study was to determine the no observed adverse effect level (NOAEL), the lowest observed adverse effect level (LOAEL) and the benchmark dose low (BMDL) of cadmium exposure by re-evaluation of the dose–response relationship between cumulative cadmium exposure and renal tubular damage reported previously. Methods: The participants were workers (326 men and 114 women) employed for at least three months between 1931 and 1982. Blood cadmium (Cd-B) and air cadmium (Cd-A) were collected at regular intervals with urinary β2-microglobulin as the tubular effect marker. Cumulative Cd-A and Cd-B were estimated by multiplying concentration and working period. The BMDL was calculated using Benchmark Dose Software (version 3.1.2). The benchmark response (BMR) was set at 5% or 10%. Results: By logistic regression, the NOAEL of mean cumulative Cd-B was 7122 months nmol/L. The LOAEL of cumulative Cd-A and least-squares cumulative Cd-B was 691 yrs μg/m3 and 8586 months nmol/L, respectively. Among various models for dose–response relationships, a probit model was adopted as the best fitting model. The obtained BMDLs of cumulative Cd-A were 272.3 yrs µg/m3 (BMR5%) and 707.5 yrs µg/m3 (BMR10%). The BMDLs of mean cumulative Cd-B were 3967.2 months nmol/L (BMR5%) and 7798.1 months nmol/L (BMR10%). The BMDLs of least-squares cumulative Cd-B were 3588.6 months nmol/L (BMR5%) and 8616.3 months nmol/L (BMR10%). Assuming a working period of 40 years, the BMDLs for BMR10% corresponded to 17.7 µg/m3 (Cd-A) and 1.8~2.0 µg/L (Cd-B). Discussion: This study provides new valuable information to enhance the reliability of limit values and thereby make a significant contribution to preventing the health effects of Cd in exposed workers.

scholarly journals Hormesis Shifts the No-Observed-Adverse-Effect Level (NOAEL)

Dose-Response ◽  
2021 ◽  
Vol 19 (1) ◽  
pp. 155932582110016
Author(s):  
Evgenios Agathokleous ◽  
Costas Saitanis ◽  
Athina Markouizou
Keyword(s):  
Adverse Effect ◽  
Anticancer Drug ◽  
Dose Response ◽  
Cancer Tissue ◽  
Toxicological Studies ◽  
Adverse Effect Level ◽  
Effect Level ◽  
Tissue Cells

Data from recent dose-response toxicological studies suggest that the no-observed-adverse-effect-level (NOAEL) may depend upon whether hormesis is present. A further examination of these data supports this hypothesis by showing that the NOAEL was greater for living units (organisms or cells) showing hormesis than for living units showing no hormesis. For example, some cancer tissue cells may exhibit hormetic responses to an anticancer drug while some other cancer tissue cells may not. These findings suggest that living units showing hormesis may also be less susceptible than living units not showing hormesis. However, these findings are preliminary and cannot be generalized or assumed to be a norm yet. New studies are needed to evaluate how NOAEL shifts depending on the occurrence of hormesis.

Selective Vulnerability of Dopaminergic Systems To Industrial Chemicals: Risk Assessment of Related Neuroendocrine Changes

1998 ◽  
Vol 14 (1-2) ◽  
pp. 311-323 ◽  
Author(s):  
Antonio Mutti ◽  
Audrey Smargiassi
Keyword(s):  
Adverse Effect ◽  
Selective Vulnerability ◽  
Common Finding ◽  
Serum Prolactin ◽  
Industrial Chemicals ◽  
Limit Values ◽  
Reference Limit ◽  
Individual Level ◽  
Adverse Effect Level ◽  
Effect Level

Increased serum prolactin (PRL) is a common finding among subjects exposed to styrene, perchloroethylene, lead (Pb), and manganese (Mn) at levels below the current threshold limit values. On a group basis, abnormally high basal PRL shows a dose-related distribution among workers exposed to styrene, Pb, and Mn. On the basis of dose-response relationships, the benchmark doses (BMD) for styrene metabolites in urine, lead in blood (Pb-B), and Mn in urine (Mn-U), are 4 mg/g creatinine, 112 μg/L, and 0.3 μg/L, respectively. Noteworthy, the BMD for Mn-U and Pb-B is well below the upper reference limit. A shift in the distribution but not in the prevalence of abnormally high values of serum PRL was observed among perchloroethylene-exposed dry cleaners, which makes interpretation in terms of risk difficult. The measurement of PRL thus provides opportunities for early identification of excess exposure to neurotoxic chemicals affecting dopaminergic control of pituitary secretion. For styrene, Pb, and Mn the BMD provides an objective and statistically determined threshold, which seems to be in good agreement with the estimated no-observed-adverse-effect-level (NOAEL). The NOAEL, however, is based on traditional approaches that require the application of uncertainty factors, e.g., a default factor of 10 when extrapolating the NOAEL from the lowest-observed- adverse-effect-level (LOAEL). Due to its sensitivity to a number of potential confounders, caution must be exercised when using PRL as a screening test at the individual level. Also, age and sex dependent variations in susceptibility may hamper extrapolations from the occupational settings to the general population.

scholarly journals Lowest observed adverse effect level of pulmonary pathological alterations due to nitrous acid exposure in guinea pigs

2020 ◽  
Vol 25 (1) ◽  
Author(s):  
Masayuki Ohyama ◽  
Hiroshi Nishimura ◽  
Kenichi Azuma ◽  
Chika Minejima ◽  
Norimichi Takenaka ◽  
...  
Keyword(s):  
Adverse Effect ◽  
Smooth Muscle ◽  
Electron Microscope ◽  
Epithelial Cells ◽  
Guinea Pigs ◽  
Pulmonary Emphysema ◽  
Nitrous Acid ◽  
Bronchial Epithelial ◽  
Adverse Effect Level ◽  
Effect Level

Abstract Background We previously demonstrated that continuous exposure to nitrous acid gas (HONO) for 4 weeks, at a concentration of 3.6 parts per million (ppm), induced pulmonary emphysema-like alterations in guinea pigs. In addition, we found that HONO affected asthma symptoms, based on the measurement of respiratory function in rats exposed to 5.8 ppm HONO. This study aimed to investigate the dose-response effects of HONO exposure on the histopathological alterations in the respiratory tract of guinea pigs to determine the lowest observed adverse effect level (LOAEL) of HONO. Methods We continuously exposed male Hartley guinea pigs (n = 5) to four different concentrations of HONO (0.0, 0.1, 0.4, and 1.7 ppm) for 4 weeks (24 h/day). We performed histopathological analysis by observing lung tissue samples. We examined samples from three guinea pigs in each group under a light microscope and measured the alveolar mean linear intercept (Lm) and the thickness of the bronchial smooth muscle layer. We further examined samples from two guinea pigs in each group under a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Results We observed the following dose-dependent changes: pulmonary emphysema-like alterations in the centriacinar regions of alveolar ducts, significant increase in Lm in the 1.7 ppm HONO-exposure group, tendency for hyperplasia and pseudostratification of bronchial epithelial cells, and extension of the bronchial epithelial cells and smooth muscle cells in the alveolar duct regions. Conclusions These histopathological findings suggest that the LOAEL of HONO is < 0.1 ppm.

1,1,2,2-Tetrafluoroethane (HFC-134) (2018)

2019 ◽  
Vol 35 (3) ◽  
pp. 196-203
Keyword(s):  
Adverse Effect ◽  
Adverse Effects ◽  
Toxicity Study ◽  
Whole Body ◽  
Exposure Level ◽  
Inhalation Toxicity ◽  
Hfc 134A ◽  
Adverse Effect Level ◽  
Effect Level ◽  
Whole Body Inhalation

1,1,2,2-Tetrafluoroethane (HFC-134) is a colorless gas used as a foam expansion agent and heat transfer fluid. HFC-134 has a low acute inhalation toxicity with an LC50 of >244,000 ppm. The no-observed adverse effect level (NOAEL) and lowest-observed adverse effect level for cardiac sensitization (in epinephrine-challenged beagle dogs) were 75,000 and 100,000 ppm, respectively. A subacute 4-week GLP inhalation toxicity study exposed male and female Crl: CD®BR rats (10/sex) to 0, 2000, 10,000, or 50,000 ppm via whole-body inhalation. Transient and non-dose-response–related body weight changes were observed throughout the exposure period, but no statistically significant, test substance-related adverse effects were observed in any clinical observations, chemistry, hematology, or pathology. This study identified a NOAEL for HFC-134 of 50,000 ppm, the highest exposure level tested. HFC-134 is not genotoxic in in vitro studies; however, no in vivo studies are available. No developmental or maternal toxicity was found in female rats exposed to HFC-134 up to 50,000 ppm via whole-body inhalation in two different studies. Based on data for a similar material (HFC-134a), HFC-134 is not expected to be extensively metabolized or to cause genetic toxicity or carcinogenicity. The HFC-134 workplace environmental exposure level (WEEL) is based primarily on the subacute 4-week inhalation toxicity study in rats with the NOAEL of 50,000 ppm selected as the point of departure for the derivation of the 8-h TWA, health-based WEEL value. The developmental toxicity study also had a NOAEL of 50,000 ppm and was the highest exposure level tested. The subacute inhalation NOAEL was adjusted to account for interindividual variability, subacute to chronic duration, animal to human extrapolation, daily duration of exposure, and residual uncertainty. In addition, the lack of adverse effects noted in the toxicology studies for HFC-134a was considered. The resulting 8-h TWA WEEL value of 1000 ppm is expected to provide a significant margin of safety against the production of any potential adverse health effects in workers following long-term inhalation exposure to HFC-134.

Toxicity Assessment of 4-Amino-2-Nitrotoluene

2013 ◽  
Vol 32 (2) ◽  
pp. 113-122 ◽  
Author(s):  
John T. Houpt ◽  
Glenn J. Leach ◽  
Larry R. Williams ◽  
Mark S. Johnson ◽  
Gunda Reddy
Keyword(s):  
Adverse Effect ◽  
Body Weight ◽  
Weight Gain ◽  
Body Weight Gain ◽  
Toxicity Study ◽  
Female Rats ◽  
Male Rats ◽  
Toxicity Data ◽  
Adverse Effect Level ◽  
Effect Level

4-Amino-2-nitrotoluene (4A2NT; CAS 119-32-4) is a degradation product of 2,4-dinitrotoluene. The toxicity data on 4A2NT are limited. Therefore, we collected toxicity data from rats to assess environmental and human health effects from exposures. The approximate lethal dose for both sexes was 5000 mg/kg. A 14-day toxicity study in rats was conducted with 4A2NT in the feed at concentrations of 0, 125, 250, 500, 1000, and 2000 ppm. Based on a 14-day oral dose range toxicity study with 4A2NT in the feed, 2000 ppm was selected as highest concentration for a subsequent 90-day study. An oral 90-day subchronic toxicity study in rats was conducted with concentrations of 0, 500, 1000, or 2000 ppm of 4A2NT in the feed. The calculated consumed doses of 4A2NT in the feed were 0, 27, 52, or 115 mg/kg/d for males and 0, 32, 65, or 138 mg/kg/d for females. A no-observed adverse effect level could not be determined. The lowest observed adverse effect level was 27 mg/kg/d for males and 32 mg/kg/d for female rats based upon decreased body weight gain. The decreased body weight gain in male rats was the most sensitive adverse event observed in this study and was used to derive a benchmark dose (BMD). A BMD of 23.1 mg/kg/d and BMD with 10% effect level of 15.5 mg/kg/d were calculated for male rats, which were used to derive an oral reference dose (RfD). The human RfD of 1.26 μg/kg/d was derived using current United States Environmental Protection Agency guidelines.

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