Subchronic and chronic inhalation toxicity of antimony trioxide in the rat

Modeling of local and systemic exposure to metals and metalloids after inhalation exposure: Recommended update to the USEPA metals framework

The USEPA issued the "Framework for Metal Risk Assessment" in 2007, recognizing that human and environmental exposure to metals and metalloids (MMEs) poses challenges risk assessment. Inhalation of aerosols containing MMEs is a primary pathway for exposure in the occupational setting, for consumer exposure, and to general population exposure associated with point-source emissions or ambient sources. The impacts of inhalation can be at the point of deposition (local exposure) or may manifest after uptake into the body (systemic exposure). Both local and systemic exposure can vary with factors that determine the regional deposition of MME-containing aerosols. Aerosol characteristics such as particle size combine with species-specific characteristics of airway morphology and lung function to modulate the deposition and clearance of MME particulates. In contrast to oral exposure, often monitored by measuring MME levels in blood or urine, inhalation exposure can produce local pulmonary impacts in the absence of significant systemic distribution. Exposure assessment for nutritionally essential MMEs can be further complicated by homeostatic controls that regulate systemic MME levels. Predictions of local exposure can be facilitated by computer models that estimate regional patterns of aerosol deposition, permitting calculation of exposure intensity in different regions of the respiratory tract. The utility of deposition modeling has been demonstrated in assessments of nutritionally essential MMEs regulated by homeostatic controls and in the comparison of results from inhalation studies in experimental animals. This facilitates extrapolation from animal data to humans and comparisons of exposures possessing mechanistic linkages to pulmonary toxicity and carcinogenesis. Pulmonary deposition models have significantly advanced and have been applied by USEPA in evaluations of particulate matter. However, regional deposition modeling has yet to be incorporated into the general guidance offered by the agency for evaluating inhalation exposure. Integr Environ Assess Manag 2023;00:1-13. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Short-term effects of the chemical components of fine particulate matter on pulmonary function: A repeated panel study among adolescents

The effects of the chemical components of fine particulate matter (PM2.5) have been drawing attention. However, information regarding the impact of low PM2.5 concentrations is limited. Hence, we aimed to investigate the short-term effects of the chemical components of PM2.5 on pulmonary function and their seasonal differences in healthy adolescents living on an isolated island without major artificial sources of air pollution. A panel study was repeatedly conducted twice a year for one month every spring and fall from October 2014 to November 2016 on an isolated island in the Seto Inland Sea, which has no major artificial sources of air pollution. Daily measurements of peak expiratory flow (PEF) and forced expiratory volume in 1 s (FEV1) were performed in 47 healthy college students, and the concentrations of 35 chemical components of PM2.5 were analyzed every 24 h. Using a mixed-effects model, the relationship between pulmonary function values and concentrations of PM2.5 components was analyzed. Significant associations were observed between several PM2.5 components and decreased pulmonary function. Among the ionic components, sulfate was strongly related to decreases in PEF and FEV1 (-4.20 L/min [95 % confidence interval (CI): -6.40 to -2.00] and - 0.04 L [95 % CI: -0.05 to -0.02] per interquartile range increase, respectively). Among the elemental components, potassium induced the greatest reduction in PEF and FEV1. Therefore, PEF and FEV1 were significantly reduced as the concentrations of several PM2.5 components increased during fall, with minimal changes observed during spring. Several chemical components of PM2.5 were significantly associated with decreased pulmonary function among healthy adolescents. The concentrations of PM2.5 chemical components differed by season, suggesting the occurrence of distinct effects on the respiratory system depending on the type of component.

Availability, Toxicology and Medical Significance of Antimony

Antimony has been known and used since ancient times, but its applications have increased significantly during the last two centuries. Aside from its few medical applications, it also has industrial applications, acting as a flame retardant and a catalyst. Geologically, native antimony is rare, and it is mostly found in sulfide ores. The main ore minerals of antimony are antimonite and jamesonite. The extensive mining and use of antimony have led to its introduction into the biosphere, where it can be hazardous, depending on its bioavailability and absorption. Detailed studies exist both from active and abandoned mining sites, and from urban settings, which document the environmental impact of antimony pollution and its impact on human physiology. Despite its evident and pronounced toxicity, it has also been used in some drugs, initially tartar emetics and subsequently antimonials. The latter are used to treat tropical diseases and their therapeutic potential for leishmaniasis means that they will not be soon phased out, despite the fact the antimonial resistance is beginning to be documented. The mechanisms by which antimony is introduced into human cells and subsequently excreted are still the subject of research; their elucidation will enable us to better understand antimony toxicity and, hopefully, to improve the nature and delivery method of antimonial drugs.

Electrocardiogram abnormalities in antimony exposed workers in the automotive brake lining manufacturing industry: a case report

Background

Antimony is used in catalysts, pesticides, brake systems, pharmaceuticals, and synthetic fire retardants in the plastic, paint, and rubber industries. Accumulation of trivalent antimony compounds in the body can cause cardiotoxic effects and increase the risk of electrocardiogram (ECG) abnormalities and sudden death. Antimony exposure can result in action potential prolongation, causing a cardiac repolarization delay, which appears as QTc prolongation and T-wave abnormalities on the ECG. There are no studies on antimony-associated cardiac toxicity in Korea.

Case presentation

Accordingly, the present study reports cases of ECG abnormalities in workers handling antimony trisulfide at a company located in the Gyeongsangbuk-do region. Nineteen workers employed at an automobile brake lining manufacturer were exposed to antimony trisulfide dust through thermoforming, grinding, and drilling processes. In 2020, the workers were reported to work 12-hour shifts, 5 days a week. The time-weighted average (TWA) of antimony trisulfide exposure measured in workers was 0.0028 mg/m³. Two workers were excluded from the analysis due to pre-existing medical conditions (cardiovascular disease). Of the remaining 17 workers, ECG abnormalities were found in 41% (seven out of 17: four with QTc prolongation and T-wave abnormalities; two with only T-wave abnormalities; and one with only QTc prolongation).

Conclusions

This case report outlines the first few cases in Korea in which potential cardiac toxicity caused by occupational exposure to antimony was identified. However, data regarding cardiac toxicity caused by antimony exposure are still lacking in Korea; thus, additional studies are needed to identify causal relationships.

Occupational exposure to antimony trioxide: a risk assessment

OBJECTIVES

The US National Toxicology Program (NTP) recently recommended in its Report on Carcinogens Monograph for Antimony Trioxide that antimony trioxide be listed as 'reasonably anticipated to be a human carcinogen' based on sufficient evidence of carcinogenicity in experimental animals and supporting evidence from mechanistic studies. Our goal was to estimate the possible human cancer risk from occupational exposure to antimony trioxide.

METHODS

We selected data from 2-year inhalation studies in male and female mice conducted by the NTP and performed cancer dose-response analyses using cancer models and benchmark dose methods developed by the US Environmental Protection Agency. In these analyses, we generated benchmark doses and cancer slope factors for antimony trioxide, and then estimated human cancer risk under various exposure scenarios. Typical and worst-case inhalation scenarios in multiple occupational settings were used in risk estimation.

RESULTS

In typical case scenarios, the occupational cancer risk from antimony trioxide was estimated to be 0.025 (25 in 1000) for persons working with flame retardants in plastics and textiles for 40 years. Under worst-case scenarios, the occupational cancer risk was estimated to be 0.11 (110 in 1000) for persons working with flame retardants in plastics and textiles. At the current Occupational Safety and Health Administration Permissible Exposure Limit, the cancer risk for occupational inhalation exposure of antimony trioxide was estimated to be 0.096 (96 in 1000).

CONCLUSION

The risk estimates calculated in this study suggest that exposure to antimony trioxide at levels present in certain occupational settings results in a large increase in the risk of developing cancer.

Antimony and its compounds: Health impacts related to pulmonary toxicity, cancer, and genotoxicity

Although occupational exposure to antimony and its compounds can produce pulmonary toxicity, human carcinogenic impacts have not been observed. Inhalation studies with respirable antimony trioxide particles administered to rats and mice have, however, induced carcinogenic responses in the lungs and related tissue sites. Genotoxicity studies conducted to elucidate mechanism(s) for tumor induction have produced mixed results. Antimony compounds do not induce gene mutations in bacteria or cultured mammalian cells, but chromosome aberrations and micronuclei have been observed, usually at highly cytotoxic concentrations. Indirect mechanisms of genotoxicity have been proposed to mediate these responses. In vivo genotoxicity tests have generally yielded negative results although several positive studies of marginal quality have been reported. Genotoxic effects may be related to indirect modes of action such as the generation of excessive reactive oxygen species (ROS), altered gene expression or interference with DNA repair processes. Such indirect mechanisms may exhibit dose-response thresholds. For example, interaction of ROS with in vivo antioxidant systems could yield a threshold for genotoxicity (and cancer) only at concentrations above the capacity of antioxidant defense mechanisms to control and/or eliminate damage from ROS.

Risk of Cancer for Workers Exposed to Antimony Compounds: A Systematic Review

BACKGROUND

Antimony (Sb) trioxide and antimony trisulfide are "2B: Possibly carcinogenic to humans" and "3: Unclassifiable" according to the International Agency for Research on Cancer (IARC). The U.S. National Toxicology Program (NTP) concluded that antimony trioxide "is reasonably anticipated to be a human carcinogen based on studies in rats and mice". We investigated the cancer hazard of antimony compounds for workers, a population with high exposure to antimony substances.

METHODS

Using the "Guidelines for performing systematic reviews in the development of toxicity factors" (Texas Commission on Environmental Quality (TCEQ) 2017) as a guidance, we established a human and an animal toxicology data stream in Medline and ToxLine. Data from this review were applied in a human health risk assessment.

RESULTS

A final pool of 10 occupational and 13 animal toxicology articles resulted after application of TCEQ guidelines.

CONCLUSIONS

Antimony carcinogenicity evidence involving workers is inadequate, based on confounding, small sample sizes, incomparability across studies, and inadequate reference populations. An increased lung cancer risk cannot be excluded. Evidence for lung neoplasms caused by antimony trioxide inhalation in experimental animals is sufficient. Overall, carcinogenicity in workers is probable (International Agency for Research on Cancer (IARC) 2A). It remains unclear from what occupational exposure duration and dose this effect arises and whether exposure threshold values should be reconsidered.

Antimony-Induced Neurobehavioral and Biochemical Perturbations in Mice

Groundwater used for drinking has been contaminated with naturally occurring inorganic arsenic and other metals, and metal-contaminated drinking water is the biggest threat to public health in Bangladesh. Toxic metals present in the drinking water have a strong relationship with chronic diseases in humans. Antimony (Sb), a naturally occurring metal, has been reported to be present in the drinking water along with other heavy metals in Bangladesh. Although Sb is present in the environment, very little attention has been given to the toxic effects of Sb. The present study was designed to investigate the in vivo effects of Sb on neurobehavioral changes like anxiety, learning and memory impairment, and blood indices related to organ dysfunction. Mice exposed to antimony potassium-tartrate hydrate (Sb) (10 mg/kg body weight) significantly (p < 0.05) decreased the time spent in open arms while increased the time spent in closed arms compared to the control mice in elevated plus maze. The mean latency time of control group to find the platform decreased (p < 0.05) significantly during 7 days learning as compared to Sb-treated group in Morris water maze test, and Sb-exposed group spent significantly (p < 0.05) less time in the desired quadrant as compared to the control group in probe trial. Sb treatment also significantly altered blood indices related to liver and kidney dysfunction. Additionally, Sb-induced biochemical alterations were associated with significant perturbations in histological architecture of liver and kidney of Sb-exposed mice. These data suggest that Sb has a toxic effect on neurobehavioral and biochemical changes in mice.

The application of non-default uncertainty factors in the U.S. EPA's Integrated Risk Information System (IRIS). Part I: UF(L), UF(S), and "other uncertainty factors"

The United States Environmental Protection Agency's Integrated Risk Information System (IRIS) includes hazard identification and dose-response assessment values developed by Agency scientists. Uncertainty factors (UFs) are used in the development of IRIS values to address the lack of information in five main areas. The standard UFs account for interspecies uncertainty (UF(A)) and intraspecies variability (UF(H)). The UF(A) addresses uncertainty related to the extrapolation of data from animals to humans, whereas the UF(H) addresses variability amongst individuals (i.e., intrahuman). Additional UFs have been employed to account for database incompleteness, extrapolations from a lowest-observed-adverse-effect level in the absence of a no-observed-adverse-effect level (UF(L)), and subchronic-to-chronic extrapolation (UF(S)). A sixth UF designated as "other uncertainty factors" (UF(O)) has also been applied in place of the UF(L) to account for uncertainty with the adversity of points of departure obtained using benchmark dose modeling. This review will discuss how UF(L), UF(S), and UF(O) have been applied in IRIS assessments, along with the rationale used to describe the choice of UF values that deviate from the standard default of 10.

Long term lung retention studies of 125Sb aerosols in humans

This paper describes the retention of 125Sb oxide aerosols in human lungs based on the data obtained from a group of seven accidental inhalation exposure cases. Long-term follow-up studies for periods of time ranging from 1 to 3 d post intake to 199 to 2,422 d post intake have indicated the biological lung clearance half-time of this material ranging from about 600 to 1,100 d for non-smokers and 1,700 to 3,700 d for smokers. The retention in the lungs after 180 d in all the seven cases is found to be much more than 51% of the estimated initial alveolar deposit, which is consistent with the present ICRP criteria of assignment to the lung absorption Type S. There is little previously reported human data on this radionuclide compound. In these studies reliable information on actual time of intake, the likely type of material, and the amount of retained body/lung activity in initial days after the incident was also available, which adds to the importance of these data. The results of these studies provide a basis for firm classification and suggest that oxides of antimony need to be removed from absorption Type M (earlier class W) where these are presently listed by ICRP and be placed in absorption Type S (earlier class Y). The range of measured retained lung activities after the initial rapid clearance phase (7 d post exposure) was about 3 to 14 kBq, which was sufficient for long-term follow up studies using the whole body counters.

Altered serum cytokine and immunoglobulin levels in the workers exposed to antimony

1 Antimony (Sb), an industrial and environmental toxicant, is known to cause dermatitis and pulmonary inflammations, but the immunomodulatory effects of environmental or occupational exposure to Sb have not been reported. To initiate investigation of Sb-induced alterations of the immune system, the concentrations of the IgG subclasses, IgE, interleukin-2, interferon-gamma, and interleukin-4 in sera obtained from workers exposed to Sb through antimony trioxide manufacture were determined and compared with those of control subjects. 2 The serum levels of IgG1, an immunoglobulin involved in host defense against many microbial infections, were significantly lower in the sera of Sb-exposed individuals than the controls. The serum concentrations of IgE, an immunoglobulin mediating allergic hypersensitivity, also were lower in the Sb-exposed workers than the controls. In addition, the levels of interleukin-2 and interferon-gamma, multifunctional cytokines for T-cell mediated immunity, were lowered in the factory workers. 3 A significant positive correlation between IgG4 and urine Sb levels was found among the Sb-exposed workers, indicating a possible role of IgG4 in Sb-mediated pulmonary or skin pathogenesis. 4 The present study provides the first report on immune alterations induced by occupational exposure to Sb and suggests that Sb exposure disturbs immunohomeostasis in humans observed as a function of aberrant serum cytokine and immunoglobulin levels, which could influence health.

Subchronic feeding study of antimony trioxide in rats

Diets containing antimony trioxide were fed to male and female Wistar rats of the Alpk:APSD strain over 90 days. Dose levels were 0 (control), 1000, 5000 and 20,000 ppm (equivalent to mean daily doses of 84, 421 and 1686 mg kg(-1) in males and 97, 494 and 1879 mg kg(-1) in females). There was no effect of compound on growth or growth rate, food consumption or clinical signs. Minor changes in haematology and urine biochemistry were considered incidental to treatment. Small reductions in plasma alkaline phosphatase activity and increases in aspartate aminotransferase activity at the high dose, together with a small (ca. 10%) increase in liver weight, could be indicative of a minor effect on the liver, but in the absence of any histological effects these changes are also considered incidental to treatment. This study confirms the inert nature of antimony trioxide.

Effects of antimony on rats following 90-day exposure via drinking water

The subchronic toxicity of antimony in drinking water was studied in the rat. Male and female Sprague-Dawley rats (127-135 g body weight, 15 animals per group) were exposed to a soluble trivalent antimony salt, potassium antimony tartrate, in drinking water at concentrations of 0.5, 5, 50 and 500 ppm for 13 wk. Control rats received tap water as drinking water. An additional 10 male and 10 female rats were included in each of the control and 500 ppm groups and were given tap water for a further 4-wk recovery period after the 13-week treatment period. During treatment, the highest dose animals of both sexes consumed significantly less water and showed suppressed body weight gain. During recovery, water intake was quickly restored to that of the control groups and body weight gain was accelerated. At termination, one highest dose male had a cirrhotic liver, and three highest dose males exhibited gross haematuria. Female rats showed a dose-related decrease in serum glucose starting at 5 ppm, and rats of both sexes in the highest dose group had slightly decreased alkaline phosphatase activity and creatinine. The highest dose males had decreased red blood cell and platelet counts and increased mean corpuscular volume. Hepatic glutathione S-transferase activity was increased in the highest dose males and females and ethoxyresorufin-O-deethylase activity was increased in the highest dose males. In the highest dose groups, mild adaptive histological changes were observed in the thyroid, liver and pituitary gland of both sexes, and in the spleen of male rats and thymus of female rats. After a 4-wk recovery period, the pituitary gland of both sexes appeared normal and the changes in the liver and thyroid of both sexes became less severe. On the other hand, minimal changes persisted in the spleen of both sexes and in the thymus of males. Tissue antimony levels were dose-related and follow the order: red blood cells > > spleen, liver > kidney > brain, fat > serum. After the recovery period, antimony level in the highest dose animals decreased for all tissues except the spleen, which remained the same as before recovery. A NOAEL of 0.5 ppm antimony in drinking water, equivalent to an average intake of 0.06 mg/kg body weight/day, was established on the basis of the histological and biochemical changes observed at 5.0 ppm.

Arsenic and antimony: comparative approach on mechanistic toxicology

A chemico-toxicological similarity between arsenic and antimony exists and their toxicology is often seen. Indeed, both elements possess several common properties, e.g. they are clastogenic but not mutagenic in the trivalent state and they have a carcinogenic potential: trivalent arsenicals are known to be human carcinogens and antimony(III) oxide (by inhalation) has been shown to cause lung cancer in female rats. For years, arsenic has been known to be environmentally toxic. Elevated human exposure to this element, mostly caused by the intake of contaminated tap water, is associated with increased incidences of cancer at various sites. It is still not clear how arsenic compounds exert their genotoxic effect. It may be connected with an inhibition of DNA repair or the induction of oxidative stress. Little work has been done on the toxicology of antimony as it is less widely present in the environment. There is evidence that in mammals antimony, unlike arsenic, is not detoxified via methylation but it still remains unclear what mechanism is responsible for antimony's genotoxicity. In general, there is little information known about this element to accurately determine its impact on human health. Thus, the aim of this paper is to review current knowledge for future risk assessment and further scientific work.

Relation between pulmonary clearance and particle burden: a Michaelis-Menten-like kinetic model

OBJECTIVES

To test the validity of a Michaelis-Menten-like kinetic model of pulmonary clearance of insoluble dusts.

METHODS

Data were investigated from studies of pulmonary clearance in F344 rats exposed to antimony trioxide (Sb2O3), photocopy test toner, polyvinyl chloride powder (PVC), and diesel exhaust particles. The Michaelis-Menten-like model was used to develop a relation in which the pulmonary clearance half time was a linear function of lung burden. After combining all data, linear regression techniques were applied to investigate the underlying relations. With the estimated intercepts and slopes, the Michaelis-Menten-like kinetic parameters kmax (maximal clearance rate) and m1/2 (a characteristic lung burden at which kmax is reduced by 50%) were derived for the four dusts.

RESULTS

The experimental data fit the linear regression very well (R2 = 0.989), suggesting that pulmonary clearance for the four dusts followed Michaelis-Menten-like kinetics. Values of the intercept terms were not significantly different among the four dusts (P = 0.294), indicating that the intrinsic clearance rates of F344 rats were the same among the four experiments. The intrinsic clearance half time was estimated to be 77.8 days, leading to an estimated kmax of 0.0089 day-1. However, the slopes of the linear relations were significantly different among the four dusts (P < 0.001). Values of m1/2 were ranked in the order of: Sb2O3 (0.69 mg) < photocopy test toner (0.97 mg) < diesel exhaust (2.49 mg) congruent to PVC (2.90 mg).

CONCLUSION

This study suggests that the Michaelis-Menten-like kinetic model reasonably describes the kinetic behavior of pulmonary clearance in F344 rats. The parameters m1/2 can be used to differentiate the potency of a particular dust for impairing pulmonary clearance.

Survey of antimony workers: mortality 1961-1992

The mortality of a census population and a prospective cohort of men employed on an antimony smelter in the north east of England was followed up from 1961-1992. The workers studied were exposed to a variety of agents including antimony and its oxides, arsenic and arsenic oxides, sulphur dioxide, and polycyclic aromatic hydrocarbons. The regional mortality rates were used to calculate expected deaths and a group of zircon sand workers employed on the site were used as a comparison group. For the census population of men working on the smelter before 1961 a significant increase in deaths from lung cancer was found (32 observed v 14.7 expected, P < 0.001). A similar excess was seen among maintenance men (12 observed v 5.3 expected P = 0.016). No such excess was found in the cohort recruited after 1960 (5 observed v 9.2 expected, maintenance workers 3 observed v 2.8 expected). There was evidence of a minimum latency period of around 20 years between first exposure and death from lung cancer. No evidence was found for a correlation between length of time worked and mortality from lung cancer. The results show that an increased risk of lung cancer existed in the workers employed before 1961, but it was not possible to attribute this excess to any particular agent. Mortality analysed by five year calendar periods of first exposure show a lessening of effect after 1955. Although the power of the study is clearly less for more recent periods of exposure the absence of any excess in the population after 1960 is encouraging.