Lung cancer risks among lead smelter workers also exposed to arsenic

Pyrolysis of biomass harvested from heavy-metal contaminated area: Characteristics of bio-oils and biochars from batch-wise one-stage and continuous two-stage pyrolysis

This study evaluates pyrolysis products obtained from biomasses (silver grass, pine, and acacia) harvested from heavy-metal-contaminated soil. To do so, we utilized two methods: a batch one-stage pyrolysis, and a continuous two-stage pyrolysis. The study results show that the yields and characteristics of bio-oils and biochars varied depending on the pyrolysis process and the type of biomass. The two-stage pyrolysis having two reactors (auger and fluidized bed reactors) appeared to be very suitable for specific chemicals production such as acetic acid, acetol, catechol, and levoglucosan. The biochar obtained from the fluidized-bed reactor of two-stage pyrolysis had high thermal stability, high crystallinity, high inorganic content, and a small number of functional groups. In contrast, the biochar obtained from the one-stage pyrolysis had low thermal stability, low crystallinity, a high carbon content, and a large number of functional groups. The biochar obtained from the two-stage pyrolysis appeared to be suitable as a material for catalyst support and as an adsorbent. The biochar obtained from one-stage pyrolysis appeared to be a suitable as a soil amendment, as an adsorbent, and as a precursor of activated carbon. All biochars showed a negative carbon footprint. In the end, this study, which was conducted using two different processes, was able to obtain the fact that products of pyrolysis biomass contaminated with heavy metals have different characteristics depending on the process characteristics and that their utilization plans are different accordingly. If the optimal utilization method proposed through this study is found, pyrolysis will be able to gain importance as an effective treatment method for biomass contaminated with heavy metals.

Neurotoxicity of Combined Exposure to the Heavy Metals (Pb and As) in Zebrafish (Danio rerio)

Lead (Pb) and arsenic (As) are commonly occurring heavy metals in the environment and produce detrimental impacts on the central nervous system. Although they have both been indicated to exhibit neurotoxic properties, it is not known if they have joint effects, and their mechanisms of action are likewise unknown. In this study, zebrafish were exposed to different concentrations of Pb (40 μg/L, 4 mg/L), As (32 μg/L, 3.2 mg/L) and their combinations (40 μg/L + 32 μg/L, 4 mg/L + 3.2 mg/L) for 30 days. The histopathological analyses showed significant brain damage characterized by glial scar formation and ventricular enlargement in all exposed groups. In addition, either Pb or As staining inhibited the swimming speed of zebrafish, which was enhanced by their high concentrations in a mixture. To elucidate the underlying mechanisms, we examined changes in acetylcholinesterase (AChE) activity, neurotransmitter (dopamine, 5-hydroxytryptamine) levels, HPI axis-related hormone (cortisol and epinephrine) contents and neurodevelopment-related gene expression in zebrafish brain. The observations suggest that combined exposure to Pb and As can cause abnormalities in swimming behavior and ultimately exacerbate neurotoxicity in zebrafish by interfering with the cholinergic system, dopamine and 5-hydroxytryptamine signaling, HPI axis function as well as neuronal development. This study provides an important theoretical basis for the mixed exposure of heavy metals and their toxicity to aquatic organisms.

Critical aspects of the physiological interactions between lead and magnesium

Despite technological progress, exposure to lead is an ongoing problem. There are many mechanisms governing the toxic effects of lead on the human body. One such mechanism involves the interaction of this xenobiotic with bivalent metal ions, including magnesium. Literature data suggest that the competition between these elements for binding sites at the molecular and cellular levels, as well as at the systemic level, may represent an important aspect of lead toxicity in the human body. This is especially clear in the context of oxidative stress, immune response, and gene expression modifications. This review aims to summarize current knowledge regarding these issues.

Lead exposure and mortality among U.S. workers in a surveillance program: Results from 10 additional years of follow-up

BACKGROUND

A cohort of male lead-exposed workers with past blood lead levels, previously followed for mortality over 12 years, has now been followed for an additional 10 years. This has doubled the number of deaths and allowed for examination of mortality outcomes across a wide range of blood lead levels.

OBJECTIVE

Evaluate association between lead exposure and 16 causes of death.

METHODS

The cohort included male workers from 11 U.S. states enrolled in a U.S. lead surveillance program. Maximum blood lead level for each worker was abstracted from surveillance records. Mortality was assessed using the National Death Index. We conducted internal analyses via Cox regression adjusting for age, calendar time, and race. External analyses compared cohort mortality rates with those of the U.S.

POPULATION

Blood lead categories were defined as 0-<5, 5-<25, 25-<40, and ≥40 μg/dL with the two lower categories combined for outcomes with <5 deaths in the 0-<5 group.

RESULTS

The cohort (n = 58,368) was followed for a median of 19 years and experienced 6,527 deaths. Average maximum blood lead was 25.9 μg/dL and mean year of first blood lead test was 1997. Strong associations were found between blood lead level with larynx and lung cancer mortality. For these outcomes, hazard ratios and 95% confidence intervals across blood lead categories were 1.0 (ref), 1.1 (0.4-3.2), 3.4 (1.3-9.1) for larynx and 1.0 (ref), 1.6 (1.0-2.5), 2.0 (1.3-3.1), 2.9 (1.9-4.5) for lung (trend p-values = 0.08 and < 0.01, respectively). Positive significant trends were also seen for mortality from brain cancer, chronic obstructive pulmonary disease, ischemic heart disease, and non-hodgkin's lymphoma. Findings suggested associations with chronic renal disease and rectal cancer mortality, although trends were not statistically significant.

CONCLUSIONS

The additional follow up confirmed previous relationships between lead and mortality and also detected new associations.

Ecogenetics of lead toxicity and its influence on risk assessment

Lead (Pb) toxicity is a public health problem affecting millions worldwide. Advances in 'omic' technology have paved the way to toxico-genomics which is currently revolutionizing the understanding of interindividual variations in susceptibility to Pb toxicity and its functional consequences to exposure. Our objective was to identify, comprehensively analyze, and curate all the potential genetic and epigenetic biomarkers studied to date in relation to Pb toxicity and its association with diseases. We screened a volume of research articles that focused on Pb toxicity and its association with genetic and epigenetic signatures in the perspective of occupational and environmental Pb exposure. Due to wide variations in population size, ethnicity, age-groups, and source of exposure in different studies, researchers continue to be skeptical on the topic of the influence of genetic variations in Pb toxicity. However, surface knowledge of the underlying genetic factors will aid in elucidating the mechanism of action of Pb. Moreover, in recent years, the application of epigenetics in Pb toxicity has become a promising area in toxicology to understand the influence of epigenetic mechanisms such as DNA methylation, chromatin remodeling, and small RNAs for the regulation of genes in response to Pb exposure during early life. Growing evidences of ecogenetic understanding (both genetic and epigenetic processes) in a dose-dependent manner may help uncover the mechanism of action of Pb and in the identification of susceptible groups. Such studies will further help in refining uncertainty factors and in addressing risk assessment of Pb poisoning.

The association between occupational lead exposure and serum levels of selected soluble receptors

The present study was designed to evaluate soluble receptors as potential targets for lead (Pb). Analyses included the serum levels of soluble Vascular Endothelial Growth Factor Receptors 2 (sVEGFR-2), soluble Epidermal Growth Factor Receptor (sEGFR), soluble Human Epidermal Growth Factor 2 (sHER-2/neu), and soluble Interleukin 6 Receptors (sIL-6R) in the groups of chronically and subchronically occupationally exposed workers. The first group consisted of 56 male workers chronically exposed to Pb. The second group (control) comprised 24 male administrative workers. The third group included 36 male workers exposed to Pb for 40 ± 3 days. Examined subjects were employed in the Pb-zinc works to perform periodic maintenance of blast furnaces and production lines. The serum levels of sHER-2/neu and sIL-6R were significantly lower in the group of workers chronically exposed to Pb compared to control values by 45% ( p < 0.05) and 44% ( p < 0.05), respectively. The values of sVEGFR-2 and sEGFR decreased after a subchronic exposure to Pb compared to baseline by 14% ( p < 0.05) and 21% ( p < 0.05), respectively. At the same time, the levels of sIL-6R also decreased by 14% ( p < 0.05). Results of the present study indicated that both chronic and subchronic occupational Pb exposures resulted in decreased levels of several soluble receptors (sVEGFR-2, sEGFR, sHER-2/neu, and sIL-6R), probably due to Pb-induced modulations of the transcription factors and metalloprotease activities, that are necessary for soluble receptor synthesis.

Individual and Combined Effects of Arsenic and Lead on Behavioral and Biochemical Changes in Mice

Arsenic (As) toxicity has caused an environmental tragedy affecting millions of people in the world. Little is known about the toxic effects of As on neurobehavioral and biochemical changes in vivo. Along this line of metal toxicity, co-exposure of lead (Pb) could aggravate the situation in the host. The present study was designed to explore the combined effects of As and Pb on behavioral changes like anxiety, spatial memory and learning impairment, and blood indices related to organ dysfunction. Exposure of mice to As (10 mg/kg body weight), Pb (10 mg/kg body weight), and As + Pb via drinking water significantly decreased the time spent exploring the open arms while it increased the time spent in the closed arms compared to control mice in the elevated plus maze. The mean latency time of the control group to find the platform decreased significantly during the learning for 7 days compared to all three treated groups in the Morris water maze test, and the As-exposed group spent significantly less time in the desired quadrant as compared to the control group in the probe trial. Both metals posed an anxiety-like behavior and deficits in spatial memory and learning, and also altered blood indices related to liver and kidney dysfunction, and a combined exposure of these metals inhibited the individual accumulation of As and Pb. Taken together, these data suggest that As has more toxic effects on neurobehavioral and biochemical changes than Pb, and there may be antagonism in the effects and accumulation between these two toxicants.

Clastogenic but Not Apoptotic Effects on Human Artery Endothelial Cells by Concentrations of Inorganic Lead Inhibiting Their Nitric Oxide Production

Human coronary artery endothelial cells (HCAEC 5156) were cultured as monolayers and exposed to concentrations of lead (as acetate, Pb) in the culture medium similar or lower than those commonly found in the blood of human beings occupationally or environmentally exposed to this element. Only at the concentration of 200 ng/mL, Pb reduced growth rate of HCAEC 5156 cells starting from the 3rd day and up to the 5th day of incubation. On the other hand, Pb (0.2, 2 and 200 ng/mL) increased concentration-dependently micronuclei formation in binucleated HCAEC5156 cells, as it was shown by the cytokinesis-blocked micronucleus assay (CBMN assay) carried out after 48 hours of exposure to the metal. However, Pb was unable, at all the above concentrations, to induce apoptosis in HCAEC 5156 cells following a 48 hour-exposure, as shown by an electrophoretic apoptotic DNA fragmentation test. Moreover, Pb (2 and 200 ng/mL) reduced significantly the concentration of nitric oxide (NO, determined analytically as L-citrulline) in both culture medium and cytosol of HCAEC 5156 cells following a 7 day-exposure to the element. Results were discussed also in relation to evidences of other studies reporting genotoxic and/or apoptotic effects of Pb on various cell types at very elevated dosages or concentrations. The observed clastogenic effects of Pb were explained through a series of mechanisms involving interactions between oxygen reactive species and NO and/or reduced NO synthesis in the endothelium, thus leading to a depressed NO bioavailability. This research first shows that Pb is provided with clastogenic but not apoptotic effects on cultured human endothelial cells. It was emphasized that such effects are induced by Pb concentrations similar to those commonly found in blood and tissues of laboratory animals showing Pb induced cardiovascular and/or neuropsychological alterations.

Relationship between blood levels of heavy metals and lung function based on the Korean National Health and Nutrition Examination Survey IV-V

BACKGROUND

Heavy metal exposure may contribute to inflammation in the lungs via increased oxidative stress, resulting in tissue destruction and obstructive lung function (OLF). In this study, we evaluated the relationship between lead and cadmium levels in blood, and lung function in the Korean population.

METHODS

Pooled cross-sectional data from 5,972 subjects who participated in the Korean National Health and Nutrition Examination Survey 2008-2012 were used for this study. OLF was defined as forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC) <0.7. Graphite-furnace atomic absorption spectrometry was used to measure levels of lead and cadmium in blood.

RESULTS

Adjusted means for age, sex, body mass index, and smoking status in blood lead and cadmium levels were increased with age and were higher in men and current smokers. The FEV1/FVC ratio was lower in the highest quartile group of lead (78.4% vs 79.0%; P=0.025) and cadmium (78.3% vs 79.2%; P<0.001) concentrations, compared with those in the lowest quartile groups. Multiple linear regression demonstrated an inverse relationship between the FEV1/FVC ratio and concentrations of lead (estimated -0.002; P=0.007) and cadmium (estimated -0.005; P=0.001). Of the 5,972 subjects, 674 (11.3%) were classified into the OLF group. Among current smokers, the risk of OLF was higher in subjects in the highest quartile group of cadmium concentration than in those in the lowest quartile group (odds ratio 1.94; 95% confidence interval 1.06-3.57).

CONCLUSION

We demonstrated a significant association between the FEV1/FVC ratio and blood concentrations of lead and cadmium in the Korean population. The risk for OLF was elevated with increasing concentrations of cadmium among current smokers.

Comparative assessment of selected metals in the scalp hair and nails of lung cancer patients and controls

Lung cancer is seriously threatening human health and exposure to trace metals is the most important aetiology for lung cancer. Selected essential/toxic metals (Ca, Mg, Na, K, Fe, Zn, Cu, Sr, Li, Co, Mn, Ni, Cr, Cd and Pb) are measured in the scalp hair and nails of lung cancer patients and controls by atomic absorption spectrophotometric method employing nitric acid-perchloric acid-based wet digestion. Average concentrations of Pb, Cd, Mn, Co and Cu are found to be significantly higher (p < 0.05) in the scalp hair and nails of lung cancer patients compared with the controls, however, appreciably higher concentrations of Zn, Ca, Na, Mg and Cr are noted in the scalp hair of the controls. Most of the metal levels reveal higher dispersion and asymmetry in the scalp hair/nails of the patients compared with the controls. Average metal levels are also compared to investigate probable differences based on sex, abode, food and smoking habits. The correlation study shows significantly diverse mutual variations of the metals in the scalp hair and nails of the patients and controls. Considerable variations in the metal levels are also noted for various stages and types of lung cancer (adenocarcinoma, squamous cell carcinoma, large cell carcinoma and small cell lung cancer). Multivariate apportionment of the metals in the scalp hair and nails of the patients and controls are also significantly diverse. The study reveals considerably divergent variations in the metal levels in lung cancer patients in comparison with healthy subjects.

Trends in arsenic levels in PM10 and PM 2.5 aerosol fractions in an industrialized area

Arsenic is a toxic element that affects human health and is widely distributed in the environment. In the area of study, the main Spanish and second largest European industrial ceramic cluster, the main source of arsenic aerosol is related to the impurities in some boracic minerals used in the ceramic process. Epidemiological studies on cancer occurrence in Spain points out the study region as one with the greater risk of cancer. Concentrations of particulate matter and arsenic content in PM10 and PM2.5 were measured and characterized by ICP-MS in the area of study during the years 2005-2010. Concentrations of PM10 and its arsenic content range from 27 to 46 μg/m(3) and from 0.7 to 6 ng/m(3) in the industrial area, respectively, and from 25 to 40 μg/m(3) and from 0.7 to 2.8 ng/m(3) in the urban area, respectively. Concentrations of PM2.5 and its arsenic content range from 12 to 14 μg/m(3) and from 0.5 to 1.4 ng/m(3) in the urban background area, respectively. Most of the arsenic content is present in the fine fraction, with ratios of PM2.5/PM10 in the range of 0.65-0.87. PM10, PM2.5, and its arsenic content show a sharp decrease in recent years associated with the economic downturn, which severely hit the production of ceramic materials in the area under study. The sharp production decrease due to the economic crisis combined with several technological improvements in recent years such as substitution of boron, which contains As impurities as raw material, have reduced the concentrations of PM10, PM2.5, and As in air to an extent that currently meets the existing European regulations.

Inhaled lead exposure affects tracheal responsiveness and lung inflammation in guinea pigs during sensitization

Total and differential white blood cells (WBC), and cytokines, levels in serum were examined in guinea pigs exposed to inhaled lead acetate. Different groups of guinea pigs including: control (group C), sensitized group (group S), and exposed animals to aerosol of three lead concentrations during sensitization (n = 6 for each group) were studied. Total and differential WBC counts of lung lavage, serum cytokine (IFNγ and IL-4), levels and tracheal responsiveness to methacholine and ovalbumin were measured. All measured values were significantly increased except for IFNγ/IL-4 ratio which was significantly decreased in nonexposed sensitized and those exposed to all lead concentrations compared to control group (p < 0.05 to p < 0.001). Most measured values in animals exposed to higher lead concentration were also significantly higher than group S except for tracheal responsiveness to methacholine and lymphocyte count. Lead concentration significantly increased in lung tissues of animals exposed to all three lead concentrations (p < 0.001 for all cases). These results showed that lead exposure during sensitization can induce greater increase in tracheal responsiveness, total WBC, eosinophil, neutrophil, and basophil counts as well as serum level of IL-4. It can also cause a decrease in lymphocyte count, IFNγ level, and IFNγ/IL-4 ratio especially in its high concentration. Therefore inhaled lead exposure may cause increased severity of asthma during development of the disease.

The effect of lead exposure on tracheal responsiveness to methacholine and ovalbumin, total and differential white blood cells count, and serum levels of immunoglobulin E, histamine, and cytokines in guinea pigs

The effect of exposure to inhaled lead acetate in guinea pigs was evaluated. The present study comprised of five groups of guinea pigs including control (C), sensitized to ovalbumin (OA; S) and three groups exposed to 0.1, 0.2, and 0.4 M inhaled lead (Pb; n = 6 for each group). Tracheal responsiveness to methacholine and OA, total and differential white blood cells (WBCs) count in lung lavage, serum levels of cytokines (interferon γ (IFN-γ) and interleukin 4 (IL-4)), histamines, and immunoglobulin E (IgE), and Pb concentration in lung were measured. Tracheal responsiveness to methacholine, OA, total and differential WBC types as well as IL-4, IFN-γ, histamine, and IgE were significantly increased but IFN-γ/IL-4 were significantly decreased in sensitized animals as well as those exposed to high Pb concentrations when compared with the control group (from p < 0.05 to p < 0.001). In addition, there was not a significant difference in most measured values between animals exposed to high Pb concentration and group S. The Pb concentration in lung tissues of animals exposed to all three Pb concentrations was significantly higher than that of group C (p < 0.001 for all cases).These results showed that inhaled lead acetate exposure can induce lung inflammatory changes similar to sensitized animals. Therefore, exposure to environmental Pb pollution may cause asthma-like changes.

Tracheal responsiveness to methacholine and ovalbumin; and lung inflammation in guinea pigs exposed to inhaled lead after sensitization

The association between lead exposure and asthma is controversial. The effect of inhaled lead acetate on lung inflammation, tracheal responsiveness and immune components in guinea pigs after sensitization was examined in this study. Five groups of guinea pigs were randomly allocated to control (group C), sensitized (group S), and three test groups exposed to inhaled lead concentrations 0.1, 0.2 and 0.4M Pb after sensitization (n=6 for each group). The measured variables included tracheal responsiveness to methacholine and ovalbumin (OA); total and differential white blood cells (WBC) counts of lung lavage; serum cytokine levels (IFN-γ and IL-4); and lead concentration in lung tissue. Tracheal responsiveness to methacholine and OA; total and differential WBC counts; IL-4 and IFN-γ were significantly increased in sensitized animals compared to control group (p<0.05 to p<0.001). However, the ratio of IFN-γ/IL-4 were significantly decreased in group S (p<0.05). In addition, all measured parameters in animals exposed to highest lead concentration and most of them in animals exposed to medium lead concentration were significantly higher than group S, except for the IFN-γ and IFN-γ/IL-4 ratio, which were significantly decreased (p<0.05 to p<0.001). The lead concentration in lung tissues of all test animals was significantly higher than that of group C (p<0.001 for all groups). These results showed that lead acetate exposure can cause further increase in tracheal responsiveness to methacholine and OA, total and differential WBC count and IL-4, IFN-γ and IFN-γ/IL-4 ratio. Therefore, environmental exposure to lead may aggravate the severity of asthma.

Respiratory symptoms and pulmonary function testes in lead exposed workers

Background

The exposure to noxious agwents such as lead my cause lung disorders.

Objectives

In the present study, pulmonary function tests and self-reported respiratory symptoms in lead exposure workers were compared with matched control subjects.

Materials and Methods

The frequency of respiratory symptoms were evaluated in a sample of 108 lead exposure workers and 100 control subjects with similar age using a questionnaire including questions on respiratory symptoms in the past year. Pulmonary function tests (PFT) were also measured in lead exposure workers and in controls.

Results

Most lead exposure workers (63%) reported work-related respiratory symptoms. Chest tightness (26%), cough (17%) and sputum (16%) were the most common symptoms and only 6% of lead exposure workers reported wheezing (P < 0.001 for all case except wheezing). Most PFT values were also significantly reduced among lead exposure workers (P < 0.05 to P < 0.001 except MEF75, MEF50, MEF25, and MMEF. The lead concentration in urine and serum of lead exposure workers were significantly higher than control (P < 0.001 for both cases).

Conclusions

These results showed that c lead exposure workers have higher frequencies of respiratory symptoms higher serum and urine lead concentration but lower PFT values.

Real-Time Voltammetric Assay of Lead Ion in Biological Cell Systems

Trace lead detection for cyclic voltammetry (CV) and square-wave (SW) stripping voltammetry was performed using mercury immobilized onto a carbon nanotube electrode (HNPE). Using the characteristics of mercury and the catalytic carbon nanotube structure, a modified technique, the 0.45 µg/l detection limit of lead ion was attained. The developed method can be applied to pond water, fish tissue, plant tissue, and in vivo direct assay.

Lung cancer mortality at a UK tin smelter

BACKGROUND

An earlier study of mortality among male former employees at a tin smelter in Humberside, UK, had identified excess mortality from lung cancer, which appeared to be associated with occupational exposure.

AIMS

The aim of the present study was to investigate the relationship between lung cancer mortality and quantitative measures of exposure.

METHODS

Using available records of occupational hygiene measurements, we established exposure matrices for arsenic, cadmium, lead, antimony and polonium-210 ((210)Po), covering the main process areas of the smelter. We established work histories from personnel record cards for the previously defined cohort of 1462 male employees. Three different methods of extrapolation were used to assess exposures prior to 1972, when no measurement results were available. Lung cancer mortality was examined in relation to cumulative inhalation exposure by Poisson regression analysis.

RESULTS

No significant associations could be found between lung cancer mortality and simple cumulative exposure to any of the substances studied. When cumulative exposures were weighted according to time since exposure and attained age, significant associations were found between lung cancer mortality and exposures to arsenic, lead and antimony.

CONCLUSIONS

The excess of lung cancer mortality in the cohort can most plausibly be explained if arsenic is the principal occupational carcinogen (for which the excess relative risk diminishes with time since exposure and attained age) and if there is a contribution to excess mortality from an enhanced prevalence of smoking within the cohort. The implications of the dose-response for arsenic exposure for risk estimation merit further consideration.

Lung cancer and occupation in nonsmokers: a multicenter case-control study in Europe

BACKGROUND

Tobacco smoking is the main cause for lung cancer worldwide, making it difficult to examine the carcinogenic role of other risk factors because of possible confounding by smoking. Therefore, the present study aimed to investigate the association between lung cancer and occupation independent of smoking.

METHODS

A case-control study of lung cancer was carried out between March 1998 and January 2002 in 16 centers from 7 European countries, including 223 never-smoking cases and 1039 controls. Information on lifestyle and occupation was obtained through detailed questionnaires. Job and industries were classified as entailing exposure to known or suspected carcinogens; in addition, expert assessment provided exposure estimates to specific agents.

RESULTS

The odds ratio of lung cancer among women employed for more than 12 years in suspected high-risk occupations was 1.75 (95% confidence interval = 0.63-4.85). A comparable increase in risk was not detected for employment in established high-risk occupations or among men. Increased risk of lung cancer was suggested among individuals exposed to nonferrous metal dust and fumes, crystalline silica, and organic solvents.

CONCLUSION

Occupations were found to play a limited role in lung cancer risk among never-smokers. Jobs entailing exposure to suspected lung carcinogens should receive priority in future studies among women. Nonferrous metal dust and fumes and silica may exert a carcinogenic effect independently from smoking.

Brain cancer mortality and potential occupational exposure to lead: findings from the National Longitudinal Mortality Study, 1979-1989

We evaluated the association between potential occupational lead exposure and the risk of brain cancer mortality in the National Longitudinal Mortality Study (NLMS), which is a prospective census-based cohort study of mortality among the noninstitutionalized United States population (1979-1989). The present study was limited to individuals for whom occupation and industry were available (n = 317,968). Estimates of probability and intensity of lead exposure were assigned using a job-exposure matrix (JEM). Risk estimates for the impact of lead on brain cancer mortality were computed using standardized mortality ratio (SMR) and proportional hazards and Poisson regression techniques, adjusting for the effects of age, gender and several other covariates. Brain cancer mortality rates were greater among individuals in jobs potentially involving lead exposure as compared to those unexposed (age- and gender-adjusted hazard ratio (HR) = 1.5; 95% confidence interval (CI) = 0.9-2.3) with indications of an exposure-response trend (probability: low HR = 0.7 (95% CI = 0.2-2.2), medium HR = 1.4 (95% CI = 0.8-2.5), high HR = 2.2 (95% CI = 1.2-4.0); intensity: low HR = 1.2 (95% CI = 0.7-2.1), medium/high HR = 1.9 (95% CI = 1.0-3.4)). Brain cancer risk was greatest among individuals with the highest levels of probability and intensity (HR = 2.3; 95% CI = 1.3-4.2). These findings provide further support for an association between occupational lead exposure and brain cancer mortality, but need to be interpreted cautiously due to the consideration of brain cancer as one disease entity and the absence of biological measures of lead exposure.

Lung Cancer Development in Primary Smelter Workers: A Nested Case-Referent Study

OBJECTIVE

The objective of this study was to study the impact of work-related exposure to mainly arsenic and lead versus smoking in primary smelter workers developing lung cancer.

METHODS

In a cohort of 3979 primary smelter workers, 46 subjects had contracted respiratory malignancies. They were compared with 141 age-matched male referents by conditional logistic regression analysis.

RESULTS

Cases showed a significantly higher smoking rate as compared with referents: odds ratio (OR) = 4.0; 95% confidence interval (CI) = 1.6-10.1; P = 0.003. When restricted to smokers (33 cases, 63 referents), the cumulative air arsenic exposure index, but not the lead exposure indices, was significantly higher among the cases: OR = 1.07; 95% CI = 1.02-1.11; P = 0.005.

CONCLUSIONS

Cumulative arsenic exposure and smoking were identified as risk factors for the development of lung cancer; lead exposure, however, was not.

Blood lead levels of the battery and exhaust workers and their pulmonary function tests

In an attempt to understand the impact of inhaled lead on the pulmonary functions, we assessed the blood lead levels and pulmonary functions of the battery and exhaust workers who are potential candidates for lead inhalation. The hospital staff served as control group. The measurements of lead levels were performed using atomic absorption spectrophotometry. Pulmonary function tests (PFTs) were performed using a portable spirometer. The blood lead levels of the battery workers, exhaust workers and controls were found to be 36.83, 26.94 and 14.81 microg/dl, respectively. The values of the workers were significantly higher than the controls (p < 0.001). The lead levels of the battery workers were also significantly higher than the exhaust workers (p < 0.001). PFT results (maximum voluntary ventilation, forced expiration flow and first forced expiration volume values of the workers) were significantly worse than the controls, and their pulmonary function test results were consistent with restrictive problems in the airways.

DNA as an enzyme. The effect of imidazole derivatives as cofactors and metal ions as activators or inhibitors

OBJECTIVE

A highly sensitive spectrofluorometric method using dichlorofluorescin (LDCF) was employed to study the rate of electron transfer reaction in presence of DNA and some imidazole derivatives.

RESULTS

In our experiments, DNA possessed a unique enzyme like catalytic function in oxidative conversion of nonfluorescent LDCF to fluorescent dichlorofluorescein (DCF). The rate enhancement was associated with the turn over constant: k(p) = 10 s(-1) for DNA and cinnamoyl imidazole as a cofactor. A biphasic saturation curve was observed when the reaction velocities were measured at fixed concentrations of DNA and variable amounts of carnosine. Each of the biphasic trends gave the Scatchard values of V(m1)/K(m1) = 3.1 x 10(-5) and V(m2)/K(m2) = 5.1 x 10(-6) with K(m1) = 2.7 x 10(-5) M and K(m2) = 4.2 x 10(-4) M for carnosine. Although Ni (II) and Pb (II) induced inhibition in the rate of electron transfer reaction in presence of DNA and cinnamoyl imidazole or carnosine, metal ions such as Mg (II), Cd (II), Zn (II) and Fe (II) caused activation of DNA. The rates of the reactions showed strong dependency on electronegativity and conductivity of metal ions, namely the increase in activity of DNA in presence of each metal ion correlated inversely with the electronegativities of the metal and was also related directly to the conductivities of individual metal. These effects were observed both in activation and also inhibition of DNA reaction. Imidazole compounds, e.g., Histidine, N-trans cinnamoyl imidazole and imidazole along with Cd (II) produced further rate enhancement. The increase was several times greater with N-trans cinnamoyl imidazole.

CONCLUSIONS

This effect could provide additional evidence for the importance of an intermediary cofactor that could facilitate the transfer of the electron from the reaction site to the DNA conductive chord. This was most guaranteed by the conjugated system provided by a compound such as N-trans cinnamoyl imidazole.