Inhalation exposure of cadmium workers: effects of respirator usage

The level of toxic and essential trace elements in hair of petrochemical workers involved in different technological processes

The objective of the investigation is comparative analysis of hair trace element content in workers of different departments of petrochemical plant. A total of 75 men working in office (engineers), and departments 1 (D₁), 3 (D₃), and 4 (D₄) of the petrochemical plant, as well as occupationally non-exposed persons, were examined. Hair trace element levels were analyzed using inductively coupled plasma mass spectrometry. The office workers were characterized by the highest hair As, Hg, Sn, I, and Si content as compared to the workers of other departments, whereas the level of those elements did not differ significantly from the control values. It is notable that hair Be levels in all employees of petrochemical plant were significantly lower, whereas Se content was significantly higher than that in unexposed controls. Hair toxic trace element content in workers directly involved in industrial processes did not differ significantly or was lower than that in the control group. At the same time, the highest levels of essential trace elements (Cr, Fe, and I) were observed in employees working in primary oil refining (D₁). Hair levels of Co, I, and Li were maximal in persons of sulfur and bitumen-producing division (D₄). The lowest levels of both essential and toxic trace elements in hair were detected in employees involved in production of liquefied gas, kerosene, and diesel fuel (D₃). The obtained data demonstrate that involvement in different technological processes in petrochemical complex differentially affect hair trace element content in workers.

Criteria for the collection of useful respirator performance data in the workplace

Workplace protection factors (WPFs) are intended to measure the ability of a respiratory protective device (RPD) to reduce contaminant exposure when used in the context of an effective respiratory protection program. In 1992, members of the American Industrial Hygiene Association Respiratory Protection Committee (RPC) published a review of important issues and considerations for measuring respirator performance in the workplace. The RPC recognized that respirator testing in workplaces can have a variety of objectives and endpoints, and that not all workplace measurements are WPFs. That paper addressed concerns in the general categories of 1) study objectives; 2) site selection; 3) subject selection and preparation; 4) sampling and analytical methods; and 5) data analysis. No specific protocol for measuring WPFs was recommended by the RPC, and attempts to reach a U.S. consensus on a WPF protocol since 1992 have not succeeded. Numerous studies have implemented the principles for WPF measurement described in the RPC paper. Modifications to the original recommendations have been made to reflect the current state of the art. This article describes what has been learned in recent years in each of the five categories identified in the 1992 discussion. Because of the wide variety of workplaces and work activities, contaminants and respiratory protective devices, a strict protocol is not appropriate for collecting WPF data. Rather, the minimum requirements for the collection and presentation of meaningful respirator performance data in the workplace are described. Understanding of these principles will permit useful RPD performance data to be generated.

Cadmium and lung cancer mortality accounting for simultaneous arsenic exposure

OBJECTIVES

Prior investigations identified an association between airborne cadmium and lung cancer but questions remain regarding confounding by arsenic, a well-established lung carcinogen.

METHODS

A cadmium smelter population exhibiting excess lung cancer was re-analysed using a retrospective exposure assessment for arsenic (As), updated mortality (1940-2002), a revised cadmium (Cd) exposure matrix and improved work history information.

RESULTS

Cumulative exposure metrics for both cadmium and arsenic were strongly associated making estimation of their independent effects difficult. Standardised mortality ratios (SMRs) were modelled with Poisson regression with the contribution of arsenic to lung cancer risk constrained by exposure-response estimates previously reported. The results demonstrate (1) a statistically significant effect of Cd independent of As (SMR=3.2 for 10 mg-year/m(3) Cd, p=0.012), (2) a substantial healthy worker effect for lung cancer (for unexposed workers, SMR=0.69) and (3) a large deficit in lung cancer mortality among Hispanic workers (SMR=0.27, p=0.009), known to have low lung cancer rates. A supralinear dose-rate effect was observed (contribution to risk with increasing exposure intensity has declining positive slope). Lung cancer mortality was somewhat better predicted using a cadmium burden metric with a half-life of about 20-25 years.

CONCLUSIONS

These findings support an independent effect for cadmium in risk of lung cancer mortality. 1/1000 excess lifetime risk of lung cancer death is predicted from an airborne exposure of about 2.4 μg/m(3) Cd.

Toxicological aspects of cadmium and occupational health activities to prevent workplace exposure in Japan: A narrative review

Chemicals are an essential part of modern manufacture processes. Their use must be managed with great attention in occupational settings to avoid serious detrimental effects to the health of employees. For example, cadmium compounds are indispensable for the production of nickel-cadmium rechargeable batteries or as chemical stabilizer in plastics. It is an exceptionally toxic heavy metal and personnel exposed to cadmium in the workplace meet with potential health risks that can lead to the development of kidney, skeletal and respiratory disorders. In consequence, proactive and systematical development of occupational hygiene and health activities are necessary to reduce chemical exposure to cadmium in the workplace. This review describes the known facts of cadmium toxicity, the biological effects of cadmium exposure, possible regulation measures to prevent occupational cadmium exposure in three industrial health management systems and discusses future cooperation programs in these systems, proactive safety activities and occupational safety and health management strategies.

Lung cancer mortality in UK nickel-cadmium battery workers, 1947-2000

AIMS

To investigate mortality from lung cancer in nickel-cadmium battery workers in relation to cumulative exposure to cadmium hydroxide.

METHODS

The mortality of a cohort of 926 male workers from a factory engaged in the manufacture of nickel-cadmium batteries in the West Midlands of England was investigated for the period 1947-2000. All subjects were first employed at the plant in the period 1947-75 and employed for a minimum period of 12 months. Work histories were available for the period 1947-86; the factory closed down in 1992. Two analytical approaches were used, indirect standardisation and Poisson regression.

RESULTS

Based on serial mortality rates for the general population of England and Wales, significantly increased mortality was shown for cancers of the pharynx (observed (Obs) 4, expected (Exp) 0.7, standardised mortality ratio (SMR) 559, p<0.05), non-malignant diseases of the respiratory system (Obs 61, Exp 43.0, SMR 142, p<0.05), and non-malignant diseases of the genitourinary system (Obs 10, Exp 4.1, SMR 243, p<0.05). Non-significantly increased SMRs were shown for lung cancer (Obs 45, Exp 40.7, SMR 111) and cancer of the prostate (Obs 9, Exp 7.5, SMR 116). Estimated cumulative cadmium exposures were not related to risks of lung cancer or risks of chronic obstructive pulmonary diseases, even when exposure histories were lagged first by 10, then by 20 years.

CONCLUSIONS

The study findings do not support the hypotheses that cadmium compounds are human lung carcinogens.

Cadmium, lung and prostate cancer: a systematic review of recent epidemiological data

Cadmium (Cd) and its compounds were classified as "carcinogenic to humans (Group 1)" by IARC in 1993. The observation of an increased number of lung cancers in a U.S. cohort of cadmium-exposed workers and the finding of tumors in animals exposed to various cadmium compounds apparently played an important role in this assessment. Since this evaluation, several cohorts of cadmium exposed workers have been updated and some additional data regarding environmental exposure to cadmium and cancer risk have been published. The main purpose of this systematic review was to examine whether inclusion of the studies that were not available for the 1993 evaluation might change the overall assessment of the carcinogenic potential of cadmium compounds. A second objective was to examine whether the recent studies are qualitatively better than the older ones and whether they should receive more weight in this assessment. A third issue was to investigate whether a competing effect between nonmalignant respiratory disease (NMRD) and lung cancer may have affected the results for lung cancer in occupationally exposed cohorts. Overall, considering the results of the most recent studies does not suggest that the effect of cadmium on lung cancer increases with improvement of the study design but points to a lower relative risk in the groups exposed to cadmium in the absence of arsenic and nickel. No evidence was found to support the hypothesis that NMRD represents a competing cause of death reducing the mortality from lung cancer. The association between cadmium exposure and prostate cancer was not confirmed in the latest available updates. Studies in environmentally exposed populations do not indicate an increased relative risk of cancer.

Lung cancer mortality in a cohort of workers employed at a cadmium recovery plant in the United States: an analysis with detailed job histories

OBJECTIVES

To identify and measure any relations between occupational exposure to cadmium compounds (oxide, sulphide, and sulphate) and the risk of mortality from lung cancer.

METHODS

The mortality experience of 571 male production workers from a cadmium recovery facility in the United States was investigated for the period 1940-82. All study subjects were first employed in the period 1926-69; they had all been employed for at least six months between 1 January 1940 and 31 December 1969. Newly abstracted detailed job histories for the period 1926-76 were combined with assessments of exposures to cadmium over time to develop individual estimates of cumulative exposure to cadmium (total exposure and exposures received both in the presence and absence of "high" exposures to arsenic trioxide). Poisson regression was used to investigate risks of mortality from lung cancer in relation to four concentrations of cumulative exposure to cadmium (< 400, 400-999, 1000-1999, > 2000 mg.m-3.days).

RESULTS

After adjustment for age attained, year of hire, and Hispanic ethnicity, there was a significant positive trend (P < 0.05) between cumulative exposure to cadmium and risks of mortality from lung cancer. Relative to a risk of unity for the lowest exposure category (first level), risks were 2.30 (95% confidence interval (95% CI) 0.72 to 7.36), 2.83 (95% CI 0.75 to 10.72), and 3.88 (95% CI 1.04 to 14.46) for the second, third, and fourth categories, respectively. Similar findings were obtained after adjustment for age only. Trends were more pronounced when employment histories were lagged first by 10 years and then by 20 years. A separate analysis examined the independent effects of exposure to cadmium received in the presence of high exposures to arsenic trioxide (mainly cadmium oxide) and exposures to cadmium received without such exposure to arsenic (mainly cadmium sulphide and cadmium sulphate). A significant trend for a risk of lung cancer was found only for exposures to cadmium received in the presence of arsenic trioxide.

CONCLUSIONS

Hypotheses which are consistent with the study findings include: (a) cadmium oxide in the presence of arsenic trioxide is a human lung carcinogen, (b) cadmium oxide and arsenic trioxide are human lung carcinogens and cadmium sulphate and cadmium sulphide are not (or they are less potent carcinogens), or (c) arsenic trioxide is a human lung carcinogen and cadmium oxide, cadmium sulphate, and cadmium sulphide are not. There were only 21 deaths from lung cancer available for this analysis and it is impossible to gauge which, if any, of these hypotheses are correct.

A dose-response analysis and quantitative assessment of lung cancer risk and occupational cadmium exposure

We performed a quantitative assessment of the risk of lung cancer from exposure to cadmium based on a retrospective cohort mortality study of cadmium-exposed workers. The study population consisted of white male workers who were employed for at least 6 months at a cadmium smelter between January 1, 1940, and December 31, 1969, and who were first employed at the facility on or after January 1, 1926. The study findings were analyzed using a modified life-table analysis to estimate standardized mortality ratios (SMRs), and various functional forms (i.e., exponential, power, additive relative rate, and linear) of Poisson and Cox proportional hazards models to examine the dose-response relationship. Estimates of working lifetime risk (45 years) were developed using an approach that corrects for competing causes of death. An excess in mortality from lung cancer was observed for the entire cohort (SMR = 149, 95% confidence interval (CI) = 95, 222). Mortality from lung cancer was greatest among non-Hispanic workers (SMR = 211, 95% CI = 131, 323), among workers in the highest cadmium exposure group (SMR = 272, 95% CI = 123, 513), and among workers with 20 or more years since the first exposure (SMR = 161, 95% CI = 100, 248). A statistically significant dose-response relationship was evident in nearly all of the regression models evaluated. Based on our analyses, the lifetime excess lung cancer risk at the current Occupational Safety and Health Administration standard for cadmium fumes of 100 micrograms/m3 is approximately 50 to 111 lung cancer deaths per 1000 workers exposed to cadmium for 45 years.

Nephropathy in cadmium workers: assessment of risk from airborne occupational exposure to cadmium

To assess the quantitative relation between exposure to airborne cadmium and various markers of renal tubular and glomerular function, 45 male workers employed at a plant that recovers cadmium from industrial waste and 32 male hospital workers of similar age and geographical location were examined. Cumulative external exposure to airborne cadmium (dose) was estimated from historical air sampling data, adjusted for respirator use. Increasing cadmium dose was associated with multiple renal tubular functional abnormalities, including reduced reabsorption of beta-2-microglobulin (beta-2), retinol binding protein (RBP), calcium, and phosphate. Serum creatinine concentration also increased with cadmium dose, suggesting impaired glomerular function. Mean systolic and diastolic blood pressures were higher in the cadmium workers than in the unexposed (134 v 120 mm Hg and 80 v 73 mm Hg respectively), but only systolic blood pressure was significantly associated with cadmium dose in multivariate analyses. Cadmium dose remained the most important predictor of serum creatinine concentration after controlling for age, blood pressure, body size, and other extraneous factors. Logistic regression to model the probability (prevalence) of various renal abnormalities with increasing dose of cadmium was used. The probability of multiple tubular abnormalities and raised serum creatinine concentration increased sharply at cumulative cadmium exposures exceeding 300 mg/m3 days, corresponding to working for 4.3 years at the current permissible United States exposure limit for cadmium dust.

Cadmium inhalation exposure estimates: their significance with respect to kidney and liver cadmium burden

Cadmium exposure histories based on employment records, area monitoring techniques, and personal sampling data were obtained for 82 industrially exposed workers. From these data, a time-weighted cumulative exposure index (TWE) was calculated for each worker by multiplying the length of time (ti) in a given work area by the estimated exposure conditions for that area and year (Ei) and then summing these values for the total exposure history TWE = sigma iEiti The cadmium body burden for each worker was measured directly by the in vivo prompt-gamma neutron activation technique. The cadmium content of the left kidney and the liver were measured. For the actively employed workers, a significant correlation (r = 0.70, p less than 0.001) was observed between the exposure index (TWE) and the liver cadmium burden. Furthermore, whenever the worker's liver burden exceeded 40 ppm and the exposure index exceeded 400-500 micrograms/m3 X yr, there was evidence of renal abnormalities (usually elevated urinary beta 2-microglobulin). The highest correlation (r = 0.83, p less than 0.001) was obtained between the kidney cadmium burden data and the exposure index for the active workers without evidence of kidney dysfunction. The percentage of workers with renal abnormalities was found to increase as the exposure index increased. When this relationship was examined using linear logistic regression analysis, the following model was indicated: logit p = 1.24 In TWE--8.34 where p is the individual worker's probability of being classified as having renal dysfunction.

Chronic cadmium exposures associated with kidney function effects

A follow-up study was conducted on 27 workers with a median of 25 years exposure to airborne cadmium. Two exposure groups had been selected a low exposure group of office, laboratory and supervisory personnel (n = 11, average urinary cadmium 13.1 micrograms/l); and a high exposure group of production workers with long histories of work in areas with substantial airborne cadmium (n = 16, average urinary cadmium 45.7 micrograms/l). An estimate of each subject's time-weighted-average inhalation exposure to cadmium was calculated from personal sampling data (1973-1976) and area sampling data (1943-1976). Based on the findings of another study, the average inhalation exposures in each of the work areas were adjusted for use of personal protective masks (respirators). Comparison of kidney function status between the high and low exposure groups showed a significant reduction in creatinine clearance, and increased uric acid and beta microglobulin excretion by the high group. Significant renal effects were associated with estimated average inhalation exposures of 63 micrograms/m3 over a 25 year period. The relationship between urinary cadmium excretion and cumulative exposure changed for higher exposures; this was consistent with the "critical concentration" model of cadmium's effects on the kidney.