Lung cancer in Japanese chromate workers

Hexavalent Chromium Targets Securin to Drive Numerical Chromosome Instability in Human Lung Cells

Hexavalent chromium [Cr(VI)] is a known human lung carcinogen with widespread exposure in environmental and occupational settings. Despite well-known cancer risks, the molecular mechanisms of Cr(VI)-induced carcinogenesis are not well understood, but a major driver of Cr(VI) carcinogenesis is chromosome instability. Previously, we reported Cr(VI) induced numerical chromosome instability, premature centriole disengagement, centrosome amplification, premature centromere division, and spindle assembly checkpoint bypass. A key regulator of these events is securin, which acts by regulating the cleavage ability of separase. Thus, in this study we investigated securin disruption by Cr(VI) exposure. We exposed human lung cells to a particulate Cr(VI) compound, zinc chromate, for acute (24 h) and prolonged (120 h) time points. We found prolonged Cr(VI) exposure caused marked decrease in securin levels and function. After prolonged exposure at the highest concentration, securin protein levels were decreased to 15.3% of control cells, while securin mRNA quantification was 7.9% relative to control cells. Additionally, loss of securin function led to increased separase activity manifested as enhanced cleavage of separase substrates; separase, kendrin, and SCC1. These data show securin is targeted by prolonged Cr(VI) exposure in human lung cells. Thus, a new mechanistic model for Cr(VI)-induced carcinogenesis emerges with centrosome and centromere disruption as key components of numerical chromosome instability, a key driver in Cr(VI) carcinogenesis.

Perspectives of Genetic Damage and Epigenetic Alterations by Hexavalent Chromium: Time Evolution Based on a Bibliometric Analysis

Compounds containing hexavalent chromium [Cr(VI)] have been classified as Group I human carcinogens in 1990 by the International Agency for Research on Cancer, known to induce human lung cancers. To determine the nature of Cr(VI) carcinogenesis, much has been learned about genetic damage and epigenetic alterations. On the basis of bibliometric analysis of the available literature found between 1966 and 2020, the present study investigated the evolution of author keywords; provided a summary of relevant studies focused on populations, animals/plants, or cells; and depicted the co-operation among countries or institutions and research group development. Additionally, multiomics technology and bioinformatics analysis can be a valuable tool for figuring out new biomarkers from different molecular levels like gene, RNA, protein, and metabolite and ascertaining the mechanism pathways of Cr(VI) genotoxicity and carcinogenesis.

Lung Cancer Risk in Male Dentists: A Retrospective Cohort Study in Japan, 1964–1997

It is reported that dentists are exposed to heavy metals in their clinics. To assess the risk of developing lung cancer among male Japanese dentists, we conducted a retrospective cohort study of 3,314 members of Osaka Dental Association (Osakafu-Shikaishikai). During 1964-1997, 39 were diagnosed with lung cancer, which figure was obtained from the file of the Osaka Cancer Registry. The observed number of lung cancers was compared with the expected number calculated by multiplying the number of person-years at risk by the corresponding age- and calendar time-specific incidence rate from the Osaka Cancer Registry data. The male dentists had no significantly different risk than general population.(O/E=1.01, 95%CI=0.72-1.39). Contrary to expectation, these findings indicate that Japanese dentists had almost the same overall risk of developing lung cancer as the general population.

Characteristics of chromate workers' cancers, chromium lung deposition and precancerous bronchial lesions: an autopsy study

The characteristics of lung cancers induced by inhaled chromate were studied in 13 consecutive autopsies on male ex-chromate workers. In addition to histopathology, we examined: (1) the relationship between the occurrence of lung cancer and the amount of chromium (Cr) deposited in the lung as determined by atomic absorptiometry and (2) the chronological changes in five precancerous lung lesions followed by bronchoscopy till death. Twenty-one cancers were identified, including 16 lung tumours observed either during follow-up or at autopsy. Of these 16 tumours, 13 were found in six subjects, implying a high frequency of multiple cancers. Eleven (69%) out of the 16 tumours were of squamous cell type (including carcinoma in situ), this being twice as frequent as in age-matched controls. A further characteristic was predominance in the central part of lung (69%). The lung Cr burden was very much higher [40-15,800 micrograms g-1 (dry)] in patients with lung tumours than in those without (8-28 micrograms g-1). Five of the precancerous lesions followed by bronchoscopy originated at bronchial bifurcations. Four of these cases showed a return to normal histology at autopsy even without therapy, and the other did not progress.

Mechanisms of chromium carcinogenicity and toxicity

Chromium, like many transition metal elements, is essential to life at low concentrations yet toxic to many systems at higher concentrations. In addition to the overt symptoms of acute chromium toxicity, delayed manifestations of chromium exposure become apparent by subsequent increases in the incidence of various human cancers. Chromium is widely used in numerous industrial processes, and as a result is a contaminant of many environmental systems. Chromium, in its myriad chemical forms and oxidation states, has been well studied in terms of its general chemistry and its interactions with biological molecules. However, the precise mechanisms by which chromium is both an essential metal and a carcinogen are not yet fully clear. The following review does not seek to embellish upon the proposed mechanisms of the toxic and carcinogenic actions of chromium, but rather provides a comprehensive review of these theories. The chemical nature of chromium compounds and how these properties impact upon the interactions of chromium with cellular and genetic targets, including animal and human hosts, are discussed.

Chromium and disease: review of epidemiologic studies with particular reference to etiologic information provided by measures of exposure

Dozens of epidemiologic studies have been conducted since the late 1940s in an attempt to elucidate the relationship between exposure to chromium compounds and increased rates of certain cancers observed in several industries. The relationship between employment in industries producing chromium compounds from chromite ore and lung cancer has been well established in numerous studies. The relationship between exposure to certain chromium-based pigments and chromic acid and lung cancer, although not as strong, is fairly well accepted. The data concerning emissions from stainless-steel manufacturing and disease are contradictory. Although individual studies have indicated excesses of gastrointestinal and occasionally other cancers in these industries, results are not consistent and not universally accepted. There is general agreement that chromite ore does not have an associated risk of cancer. Although the chromium compound (or compounds) responsible for disease have yet to be identified, there is general agreement that hexavalent species are responsible for these diseases and that the trivalent species are not. Hypotheses about the carcinogenicity of specific chromium compounds generally relate to their solubility in body fluids. These hypotheses, however, have generally been produced as a result of toxicologic, not epidemiologic, investigation. Well-designed epidemiologic studies incorporating detailed assessments of worker exposures have the potential to help elucidate causality, identify specific carcinogenic compounds, and quantify risk in humans, eliminating the need to extrapolate from animal data. Although the need for exposure data crucial to this effort was identified in the earliest epidemiologic studies of chromium, such studies have not been conducted. As a result, little more is known today about the relationship between this chemical and disease in humans than was known 40 years ago.

An assessment and quantitative uncertainty analysis of the health risks to workers exposed to chromium contaminated soils

Millions of tons of chromite-ore processing residue have been used as fill in various locations in Northern New Jersey and elsewhere in the United States. The primary toxicants in the residue are trivalent chromium [Cr(III)] and hexavalent chromium [Cr(VI)]. The hazard posed by Cr(III) is negligible due to its low acute and chronic toxicity. In contrast, Cr(VI) is considered a inhalation human carcinogen at high concentrations. Approximately 40 commercial and industrial properties in Northern New Jersey have been identified as containing chromite ore processing residue in the soil. One site, a partially-paved trucking terminal, was evaluated in this assessment. The arithmetic mean and geometric mean concentrations of total chromium in soil were 977 and 359 mg/kg, respectively. The data were log-normal distributed. The arithmetic mean and geometric mean concentrations of Cr(VI) in surface soil were 37.6 and 3.1 mg/kg, respectively. The data could not be fit to a standard distribution, likely due to the large number of samples with concentrations below the method detection limit (65%). Dose was calculated for each exposure route using a Monte Carlo statistical simulation. Probability distributions of most exposure parameters were incorporated into the analyses to predict the range and probability of uptake for persons in the exposed population. The exposure parameter distributions included in this assessment are: the concentrations of Cr(VI) and total chromium in air and soil, fraction of the year when suspension of airborne soil particulates is likely to occur due to weather conditions, fraction of Cr(VI) in air which is respirable (less than 10 microns), soil loading rate on skin, occupational tenure, and body weight. The techniques used in this assessment are applicable for evaluating the human health risks posed by most industrial sites having contaminated soil. The estimated average daily dose (ADD) via ingestion and dermal absorption for the individual exposed at the 95th percentile was about 48,000- and 91-fold below the U.S. EPA reference dose (RfD) for Cr(III) and Cr(VI), respectively. Since inhalation of Cr(VI) contaminated dust (but not ingestion or dermal contact) poses a cancer hazard, the lifetime average daily doses (LADDs) associated with exposure at the 50th and 95th percentile were calculated to be 9.8 x 10(-8) and 1.3 x 10(-6), respectively. Based on this analysis, industrial sites having soil concentrations of Cr(VI) below 230 ppm do not pose a significant noncarcinogenic or carcinogenic health hazard following acute or chronic exposure. These risks would be even smaller if the sites were paved.

Mortality from respiratory cancer and other causes in United Kingdom chromate production workers

This report updates a 1981 study of mortality at three United Kingdom chromate producing factories, and pays special attention to workers engaged after major plant and process changes were completed during 1958-60. The study covers 2298 payroll workers in post on 1 January 1950 or entering employment up to 30 June 1976 and remaining at least one year, with mortality observed up to 31 December 1988. Expected numbers of deaths were calculated from national death rates adjusted for social class and area differences. At the two largest factories 1422 men starting work before the process changes showed a highly significant excess of deaths from lung cancer (observed deaths/adjusted expected deaths (obs/expA) 175/88.97, adjusted standardised mortality ratio (SMRA) 197). They also had a significant excess of deaths from nasal cancer (obs/expA 4/0.26, SMRA 1538); the four affected men all had over 20 years of employment. Six hundred and seventy seven men starting work after the completion of process changes showed no excess of lung cancer deaths (obs/expA 14/13.7, SMRA 102, 95% confidence interval (95% CI) 56-171), but the possibility of the risk persisting at a reduced level cannot be excluded. The risk among earlier entrants affected men with two or more years of employment and was highest among those working for 10 years or longer (SMRA 225). The relative risk was already raised 5-14 years after first employment; it was highest in the 25-40 year period, but was still raised 50 years after first exposure. The risk showed most clearly at young ages, with a SMRA of 355 for ages under 50 (obs/expA 21/5.91). The excess was greater among men in jobs with high exposure to chromates (obs/expA 151/61.73, SMRA 245) than among men in less exposed jobs (obs/expA 21/19.57, SMRA 107). Less evidence of a lung cancer excess was found among 199 men employed at a third small factory (obs/expA 12/9.91, SMRA 121). No risk was apparent in further groups of 214 salaried works staff (obs/expA 1/2.53), or 95 workers at an adjacent fertiliser plant (obs/expA 3/3.95). No significant excesses of deaths from cancers of other sites were found.

One hundred years of chromium and cancer: a review of epidemiological evidence and selected case reports

The present review is motivated by the fact that 100 years have passed since the first cancer case in a chromium worker was reported in Scotland. Old and recent case reports and epidemiological studies among chromate workers are reviewed to elucidate the importance of valency states and water solubility of chromium compounds for carcinogenic potency. It is concluded that all chromium[VI] compounds should be considered carcinogenic among exposed populations, and that no evidence has been presented indicating that human exposure to chromium[III] is associated with increased cancer risk. Strong evidence has been presented that zinc chromate is a potent carcinogen and suggests that calcium chromate may be a potent carcinogen. Evidence also suggests that water-soluble chromates in general may be more potent carcinogens than those with low solubility. Primary and secondary prevention of chromate-related cancer and the success in preventive measures are briefly discussed, and recommendations for future research are made.

Small cell lung cancer

Lung cancer is the most common cause of cancer death in the United States, with approximately 135,000 men and women dying each year. While much has been learned about the etiologic risk factors, less progress has been made in therapy. Five-year survival rates remain at less than 10%. However, there has been some progress in the therapy of one histological subtype of lung cancer, small cell lung cancer. Totaling around 20% of lung cancer cases, small cell lung cancer is distinct from the other histologic subtypes in its biologic behavior and responsiveness to therapy. In the 1960s, the median survival for patients with small cell lung cancer was approximately 3 months. With combination chemotherapy and radiotherapy median survivals now range from 1 to 2 years, and there is evidence for a curative potential since approximately 10% of patients who initially present with limited disease survive greater than 2 years. The unique clinical aspects of this histological subtype potentially relate to its underlying cell of origin. This behavior is reflected in the numerous paraneoplastic syndromes that frequently accompany small cell lung cancer. Its propensity for early dissemination have made staging the extent of disease an important part of the clinical evaluation. Since small cell lung cancer is sensitive to both chemotherapy and radiation therapy, there have been multiple clinical trials evaluating drug/radiotherapy combinations. This article will briefly describe the unique aspects of small cell lung cancer as opposed to other histological subtypes of lung cancer and give an overview of the current clinical approach and treatment of this disease.

Lung cancer in chromate workers: high-risk group for multiple lung cancer

We diagnosed eight (8.9%) lung cancer patients in 90 workers exposed to chromate compounds. The duration of exposure ranged from 8 to 31 years, with a mean value of 18 +/- 8 years. The histological classification was squamous-cell carcinoma in seven patients and adenocarcinoma in one patient. The site of origin of the primary tumors was located peripherally in two (25%) and centrally in six (75%). All but one of these patients underwent surgery. In three (37.5%) of these patients, lung cancer foci were detected during the postoperative follow-up by sputum cytology and bronchoscopy. Two of these three patients had multicentric cancer foci: double primary early squamous-cell carcinoma in one and early squamous-cell carcinoma + small-cell lung cancer in the other. In a high-risk group such as chromate workers, we should emphasize early detection of lung cancer by serial sputum cytology, chest x-rays, and bronchoscopy. Lung cancer patients with chromate exposure should be treated with due regard to the possibility of synchronous or metachronous cancer.

Chromium content of organs of chromate workers with lung cancer

The content of chromium was measured in organs of six chromate workers who had worked in a chromate chemical manufacturing plant, had been exposed to a considerable amount of chromium for over 10 years, and had died of lung cancer. The chromium in the lungs of workers averaged 51.5 micrograms/g (range 24.8-210 micrograms/g), while levels in the lungs of non-exposed controls were 0.07-1.01 micrograms/g. Organs other than the lungs of the workers also had more chromium than those of the controls. Moreover, it was apparent that the metal remained in the lungs long after exposure to chromate had ceased.

Chromate lung cancer with special reference to its cell type and relation to the manufacturing process

The manufacturing process of the chromate industry can be classified into five steps. The main hazardous pollutants of the first step are trivalent chromate compounds, and those of the second and third steps are hexavalent chromate compounds. Analysis of the detailed working history of chromate workers with bronchogenic carcinoma, yielded the following results: the work history of chromatic lung cancer patients in the first step, which produced mainly trivalent chromate dust, was rather short. Patients with small cell carcinoma were engaged mainly in the second step (98.1% of the total working months), where they were heavily exposed to hexavalent chromate dusts. Patients with squamous cell carcinoma were engaged rather evenly in the second and fourth steps, and somewhat longer in the third step. Comparisons of the exposure periods revealed that the working history of small cell carcinoma patients was significantly shorter than that of squamous cell carcinoma patients. There were many more heavy smokers among the squamous cell carcinoma group as compared to the small cell carcinoma patients. Based on these results, it is concluded that the cell type of occupational lung cancer was mainly small cell carcinoma when the exposure to carcinogenic agents was heavy, and that the carcinogenicity of chromate was derived mainly from hexavalent chromate rather than trivalent compounds.

Bioassay of metals for carcinogenesis: whole animals

Metals have been evaluated as potential carcinogens by administering pure elements or compounds by a large variety of routes. These include mixing the agent in the food, dissolving the test compound in the drinking water, or administering the material by gavage. The respiratory tract routes tested include inhalation, intratracheal instillation, the direct injection of particulates into the pleural cavity, or the implantation of hooks by surgical intervention. The parenteral routes used were intravenous injection, intraperitoneal injection, subcutaneous implantation, as well as intrafemoral and intramuscular injection. This latter route is the most commonly used. There are major objections to the subcutaneous implantations route, and data generated from these experiments are difficult to interpret for the foreign body reaction may give rise also to fibrosarcomas. This then is a nonspecific reaction. Exotic routes tested include intrarenal, intratesticular, and intracranial injections. The endpoints of the carcinogenic reactions are, in the main, sarcomas of certain types with fibrosarcomas predominating. Rhabdomyosarcomas are the next most frequent cancer found, and squamous cell carcinoma may account for less than 2% of the cancers reported. Much more research is necessary to clarify the nature of metal carcinogenesis. Dose-response information is almost nonexistent; the divided dose problem has not been studied adequately, and very little information is available on interspecies reactions. More work is needed to help interpret the mechanism of action.

Health of workmen in the chromate-producing industry in Britain

In a follow-up study of 2715 men who had worked for at least one year at the three chromate-producing factories in Britain between 1948 and 1977 only 298 were lost to follow-up, and the average number of person-years in the study was 16.3. One hundred and sixteen deaths from lung cancer occurred in these men, with only 48.0 expected (O/E = 2.4; p less than 0.001). For men employed at the factory, which is still in operation, the relative risk of lung cancer has decreased from over 3.0 before plant modification to about 1.8 in those who have worked only since plant modification. A multivariate analysis was used in an attempt to unravel the overlapping influence of duration of employment, length of follow-up, plant modification, factory, age at entry to work, and estimated degree of chromate exposure. The major dependent factor appeared to be duration of employment; in addition the analysis suggested that modifications in the plant and work environment had been associated with an appreciable reduction of the excess risk from lung cancer.

The mammalian spot test and its use for the testing of potential carcinogenicity of welding fume particles and hexavalent chromium

Welding fume particles, potassium chromate and cyclophosphamide are tested in the mammalian spot test. Female mice C57BL/6J/BOM9 weeks old have been mated to T-stock male mice and treated with welding fume particles 100 mg/kg, potassium chromate 20 or 10 mg/kg, or cyclophosphamide 10 or 2.5 mg/kg intraperitoneally at day 8, 9 and 10 of pregnancy. The fur of the offspring was checked week 2 through week 5 after birth for coloured spots. The characterisation of the different types of spots are discussed. Welding fume particles 100 mg/kg and potassium chromate 10 mg/kg induce approximately to the same extent as cyclophosphamde 2.5 mg/kg, grayish or brownish spots in tvo screening test for mutagenic and carcinogenic potential of chemicals. The positive results for potassium chromate and cyclophosphamide are in agreement with previous in vitro experiments and confirm the sensitivity of the test. The effect of welding fume particles in this in vivo system suggests a potential risk for humans directly exposed to welding fumes.

Chromium content of lungs of chromate workers with lung cancer

The chromium content was measured in the lungs of chromate workers, obtained at necropsy in six patients and at surgery in two. The mean chromium content of peripheral lung tissue was 36.7 micrograms per gm wet weight (range 0.50 to 130.2 micrograms) and that of the large airways was 0.51 micrograms per gm wet weight (range 0.22 to 0.99 micrograms). These means values were high compared with those from control lungs of a non-chromate exposed lung cancer patients--respectively 0.21 micrograms per gm in lung tissue and 0.11 micrograms per gm in the large bronchi. The longer the exposure period, the higher was the chromium content in the lungs. The concentration of chromium in the upper lobes was significantly higher than that in the lower lobes, suggesting regional differences either in clearance from or deposition in the lung. Moreover, it was apparent that the metal remained in the lungs long after exposure to chromate had ceased