Carbon monoxide, carbon disulfide, lead and cadmium--four examples of occupational toxic agents linked to cardiovascular disease

Removal of organic pollutants in shale gas fracturing flowback and produced water: A review

Shale gas has been developed as an alternative to conventional energy worldwide, resulting in a large amount of shale gas fracturing flowback and produced water (FPW). Previous studies focus on total dissolved solids reduction using membrane desalination. However, there is a lack of efficient and stable techniques to remove organic pollutants, resulting in severe membrane fouling in downstream processes. This review focuses on the concentration and chemical composition of organic matter in shale gas FPW in China, as well as the hazards of organic pollutants. Organic removal techniques, including advanced oxidation processes, coagulation, sorption, microbial degradation, and membrane treatment are systematically reviewed. In particular, the influences of high salt on each technique are highlighted. Finally, different treatment techniques are evaluated in terms of energy consumption, cost, and organic removal efficiency. It is concluded that integrated coagulation-sorption-Fenton-membrane filtration represents a promising treatment process for FPW. This review provides valuable information for the feasible design, practical operation, and optimization of FPW treatment.

Associations between Blood Lead Levels and Coronary Artery Stenosis Measured Using Coronary Computed Tomography Angiography

BACKGROUND

Lead exposure is a risk factor for increased blood pressure and cardiovascular disease, even when blood lead levels (BLLs) are within the normal range.

OBJECTIVE

This study aimed to investigate the association between BLL and coronary artery stenosis (CAS) in asymptomatic adults using 128-slice dual-source coronary computed tomography (CT) angiography.

METHODS

We analyzed medical records data from 2,193 adults (1,461 men and 732 women) who elected to complete a screening health examination, coronary CT angiography, and BLL measurement during 2011-2018 and had no history of CAS symptoms, cardiovascular disease, or occupational exposure to lead. Logistic regression models were used to estimate associations between moderate-to-severe CAS (≥25% stenosis) and a 1-μg/dL increase in blood lead, with and without adjustment for age, sex, hypertension, diabetes mellitus, dyslipidemia, body mass index, regular exercise, smoking status, and alcohol drinking.

RESULTS

BLLs ranged from 0.12 to 10.14μg/dL, with an arithmetic mean of 2.71±1.26μg/dL. The arithmetic mean was higher for men than for women (2.98±1.26μg/dL vs. 2.18±1.08μg/dL, p<0.001) and higher in the moderate-to-severe CAS group than in the no-CAS or <25% stenosis group (3.02±1.44μg/dL vs. 2.67±1.23μg/dL, p<0.001). Moderate-to-severe CAS was significantly associated with BLL before and after adjustment, with an adjusted odds ratio for a 1-μg/dL increase in BLL of 1.14 (95% CI: 1.02, 1.26), p=0.017.

CONCLUSIONS

BLL was positively associated with the prevalence of moderate-to-severe CAS in Korean adults who completed an elective screening examination for early cardiovascular disease, 94% of whom had a BLL of <5μg/dL. More efforts and a strict health policy are needed to further reduce BLLs in the general population. https://doi.org/10.1289/EHP7351.

Cadmium and hypertension in exposed workers: A meta-analysis

OBJECTIVES

In the general population, cadmium seems to be responsible for hypertension, atherosclerosis and an increase in acute coronary events. Therefore, the purpose of this meta-analysis was to analyze controlled studies conducted on cadmium and arterial pressure in occupationally-exposed workers.

MATERIALS AND METHODS

After analyzing all the relevant articles found in the literature, 6 publications were selected.

RESULTS

A higher prevalence of hypertension and higher values of systolic and diastolic blood pressure were recorded in the exposed subjects.

CONCLUSIONS

Cadmium in occupationally-exposed individuals appears to induce an increase in systolic and diastolic blood pressure and an increase in the prevalence of hypertension.

Association of blood cadmium level with cardiometabolic risk factors and liver enzymes in a nationally representative sample of adolescents: the CASPIAN-III study

Introduction. This study aimed to determine the association of blood cadmium level with cardiometabolic risk factors and liver enzymes in adolescents. Methods. This case control study comprised 320 Iranian adolescents, 160 with metabolic syndrome and an equal number of controls. They were selected from participants of a nationwide survey entitled the CASPIAN-III study. Cadmium was measured by atomic absorption method. Results. The mean age of the case and control groups was not significantly different (15.3 ± 2.6 versus 14.63 ± 2.5 years, resp., P > 0.05). The mean cadmium level was near double-fold higher than the standards of the World Health Organization, without significant difference between the MetS and control groups (10.09 ± 2.21, 9.97 ± 2.38 μg/L, resp., P > 0.05). Cadmium level had positive but nonsignificant correlations with diastolic blood pressure, serum triglycerides, fasting blood glucose, LDL-C, and liver enzymes. Conclusion. Cadmium level had positive but nonsignificant association with some cardiometabolic risk factors and liver enzymes. The associations did not reach statistical significant level, and this may be because of the high levels of cadmium in both groups studied or because of the young age group of participants. Controlling environmental pollutants shall be a priority for the prevention of chronic diseases.

Association of blood lead concentrations with mortality in older women: a prospective cohort study

BACKGROUND

Blood lead concentrations have been associated with increased risk of cardiovascular, cancer, and all-cause mortality in adults in general population and occupational cohorts. We aimed to determine the association between blood lead, all cause and cause specific mortality in elderly, community residing women.

METHODS

Prospective cohort study of 533 women aged 65-87 years enrolled in the Study of Osteoporotic Fractures at 2 US research centers (Baltimore, MD; Monongahela Valley, PA) from 1986-1988. Blood lead concentrations were determined by atomic absorption spectrometry. Using blood lead concentration categorized as < 8 microg/dL (0.384 micromol/L), and > or = 8 microg/dL (0.384 micromol/L), we determined the relative risk of mortality from all cause, and cause-specific mortality, through Cox proportional hazards regression analysis.

RESULTS

Mean blood lead concentration was 5.3 +/- 2.3 microg/dL (range 1-21) [0.25 +/- 0.11 micromol/L (range 0.05-1.008)]. After 12.0 +/- 3 years of > 95% complete follow-up, 123 (23%) women who died had slightly higher mean (+/- SD) blood lead 5.56 (+/- 3) microg/dL [0.27(+/- 0.14) micromol/L] than survivors: 5.17(+/- 2.0) [0.25(+/- 0.1) micromol/L] (p = 0.09). Women with blood lead concentrations > or = 8 microg/dL (0.384 micromol/L), had 59% increased risk of multivariate adjusted all cause mortality (Hazard Ratio [HR], 1.59; 95% confidence interval [CI], 1.02-2.49) (p = 0.041) especially coronary heart disease (CHD) mortality (HR = 3.08 [CI], (1.23-7.70)(p = 0.016), compared to women with blood lead concentrations < 8 microg/dL(< 0.384 mumol/L). There was no association of blood lead with stroke, cancer, or non cardiovascular deaths.

CONCLUSION

Women with blood lead concentrations of > or = 8 microg/dL (0.384 micromol/L), experienced increased mortality, in particular from CHD as compared to those with lower blood lead concentrations.

Lead levels and ischemic heart disease in a prospective study of middle-aged and elderly men: the VA Normative Aging Study

BACKGROUND

Lead exposure has been associated with higher blood pressure, hypertension, electrocardiogram abnormalities, and increased mortality from circulatory causes.

OBJECTIVE

We assessed the association between bone lead-a more accurate biomarker of chronic lead exposure than blood lead-and risk for future ischemic heart disease (IHD).

METHODS

In a prospective cohort study (VA Normative Aging Study), 837 men who underwent blood or bone lead measurements at baseline were followed-up for an ischemic heart disease event between 1 September 1991 and 31 December 2001. IHD was defined as either a diagnosis of myocardial infarction or angina pectoris that was confirmed by a cardiologist. Events of fatal myocardial infarction were assessed from death certificates.

RESULTS

An IHD event occurred in 83 cases (70 nonfatal and 13 fatal). The mean blood, tibia, and patella lead levels were higher in IHD cases than in noncases. In multivariate Cox-proportional hazards models, one standard deviation increase in blood lead level was associated with a 1.27 (95% confidence interval, 1.01-1.59) fold greater risk for ischemic heart disease. Similarly, a one standard deviation increase in patella and tibia lead levels was associated with greater risk for IHD (hazard ratio for patella lead = 1.29; 95% confidence interval, 1.02-1.62).

CONCLUSIONS

Men with increased blood and bone lead levels were at increased risk for future IHD. Although the pathogenesis of IHD is multifactorial, lead exposure may be one of the risk factors.

Carbon disulfide encephalopathy: cerebral microangiopathy

To understand cerebral blood circulation after long-term exposure to carbon disulfide (CS2), four patients with encephalopathy and polyneuropathy, who had worked in a viscose rayon plant, were studied. Clinical and laboratory examinations, including brain magnetic resonance images (MRI), computed tomography (CT), CT perfusion, and CT angiography, were carried out. Brain CT and MRI disclosed mild cortical atrophy in all four patients, and multiple lesions in the subcortical white matter, and basal ganglia in three patients. Brain CT angiography and perfusion revealed a statistically significant decrease of cerebral blood flow (CBF) in the total brain parenchyma and basal ganglia, and a decrease of the cerebral blood volume (CBV) in the basal ganglia and a prolonged mean transit time (MTT) in the total brain parenchyma, and the territories of the internal carotid artery (ICA), basal ganglia and occipital lobe. In conclusion, the decrease of CBV and CBF, and the prolonged MTT in the total brain parenchyma, ICA, basal ganglia and occipital lobes, indicated a microangiopathy in patients with CS2 encephalopathy.

Diffuse White Matter Lesions in Carbon Disulfide Intoxication: Microangiopathy or Demyelination

Long-term exposure to carbon disulfide (CS(2)) may induce diffuse encephalopathy with parkinsonism, pyramidal signs, cerebellar ataxia, and cognitive impairments, as well as axonal polyneuropathy. The pathogenic mechanisms of diffuse encephalopathy are unclear, although vasculopathy and toxic demyelination have been proposed. Recently, we have encountered a patient who developed headache, limb tremors, gait disturbance, dysarthria, memory impairment, and emotional lability after long-term exposure to CS(2). The brain magnetic resonance images (MRI) showed diffuse hyperintensity lesions in T(2)-weighted images in the subcortical white matter, basal ganglia, and brain stem. The brain computed tomography perfusion study revealed a diffusely decreased regional cerebral blood flow and prolonged regional mean transit time in the subcortical white matter and basal ganglion. To our knowledge, there have been few reports demonstrating diffuse white matter lesions in chronic CS(2) encephalopathy using brain MRI. In addition, the (99m)Tc-TRODAT-1 single photon emission computed tomography showed a normal uptake of the dopamine transporter, indicating a normal presynaptic dopaminergic pathway. We conclude that diffuse white matter lesions may develop after chronic exposure to CS(2), possibly through microangiopathy. In addition, CS(2) poisoning can be considered as one of the causes of chronic leukoencephalopathy.

Brain MRI findings of carbon disulfide poisoning

OBJECTIVE

To evaluate the findings of brain MRI in patients with carbon disulfide poisoning.

MATERIALS AND METHODS

Ninety-one patients who had suffered carbon disulfide poisoning [male:female=87:4; age, 32-74 (mean 53.3) years] were included in this study. To determine the extent of white matter hyperintensity (Grade 0-V) and lacunar infarction, T2-weighted MR imaging of the brain was performed.

RESULTS

T2-weighted images depicted white matter hyperintensity in 70 patients (76.9%) and lacunar infarcts in 27 (29.7%).

CONCLUSION

In these patients, the prevalent findings at T2-weighted MR imaging of the brain were white matter hyperintensity and lacunar infarcts. Disturbance of the cardiovascular system by carbon disulfide might account for these results.

The association between occupational lead exposure and serum cholesterol and lipoprotein levels

OBJECTIVES

This study sought to clarify the possible associations between blood lead level and serum cholesterol and lipoprotein levels in subjects occupationally exposed to lead.

METHODS

Levels of blood lead, serum total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein cholesterol, and triglycerides in 56 male industrial employees who were exposed to lead were compared with those in 87 unexposed employees.

RESULTS

Mean blood lead levels were 42.3 (+/- 14.9) micrograms/dL in the exposed group and 2.7 (+/- 3.6) micrograms/dL in the nonexposed group. The exposed subjects had higher mean levels of total cholesterol and HDL cholesterol.

CONCLUSIONS

Blood lead levels are positively associated with total and HDL cholesterol.

Lipid abnormalities in rats given small doses of lead

Previous human and experimental studies have demonstrated that lead exposure may modify the metabolism of lipids. Several studies have indicated that exposure to lead produces an increase in lipid peroxidation and inhibits blood superoxide dismutase activity. Recently, lipid peroxides have been shown to impair tissue membranes and to be a risk factor for vascular diseases. The aim of the present investigation was to evaluate the impact of subclinical lead poisoning on rat lipids in the context of atherosclerosis. The degree of poisoning was analogous to that in populations exposed to lead in a contaminated environment. Experiments were performed on male Buffalo rats with body weights of 150-200 g. The experimental animals received lead acetate intragastrically in doses of 35 mg lead/kg body wt. (Pb/kg) once weekly or 70 mg Pb/kg twice weekly for 7 weeks. Control rats were fed in the same manner with sodium acetate equimolar to the acetate in the lead acetate solution. One day after the feeding was over, venous blood samples, under ether anesthesia, were collected. The animals were killed by exsanguination and the liver was excised for determination of the metal (lead, copper, and zinc) content. A segment of the abdominal aorta was excised for histological examination. In venous blood the following were estimated: triglycerides, total cholesterol, high-density lipoprotein (HDL)-cholesterol fraction, serum lipid peroxides, and blood superoxide dismutase activity. Metal content (lead, copper, and zinc) in blood and liver was determined by means of atomic absorption spectrophotometry. In rats poisoned with small doses of lead, decreases in the plasma cholesterol level and the HDL-cholesterol fraction were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipid oxidation products in food and atherogenesis

Lipid oxidation products are present in unknown amounts in the food supply of industrialized societies. Evidence for a putative role of some of these compounds in accelerating events in the atherogenic process--the initiation of endothelial injury, the accumulation of plaque, and the termination phase of thrombosis--comes from both animal and human studies. Although metabolic and epidemiological studies in humans and animals generally support the concept that a higher intake of polyunsaturates is beneficial to lipoprotein metabolism and cardiovascular health, some findings suggest that a diet high in polyunsaturated fatty acids that are insufficiently protected by antioxidants, such as vitamin E, may carry a higher risk of atherosclerosis. Although gross pathological effects of ingestion of lipid oxidation products are unlikely in the human feeding situation, more subtle metabolic actions of these compounds on vitamin E status, platelet activity, and lipoprotein metabolism cannot yet be discounted. The presence of reactive lipid oxidation components in foods needs more systematic research in terms of the metabolic effects of these compounds and their occurrence in the usual diet, as well as the associated antioxidant requirements.

Routes of formation and toxic consequences of lipid oxidation products in foods

Lipid oxidation in foods is initiated by free radical and/or singlet oxygen mechanisms which generate a series of autocatalytic free radical reactions. These autoxidation reactions lead to the breakdown of lipid and to the formation of a wide array of oxidation products. The nature and proportion of these products can vary widely between foods and depend on the composition of the food as well as numerous environmental factors. The toxicological significance of lipid oxidation in foods is complicated by interactions of secondary lipid oxidation products with other food components. These interactions could either form complexes that limit the bioavailability of lipid breakdown products or can lead to the formation of toxic products derived from non-lipid sources. A lack of gross pathological consequences has generally been observed in animals fed oxidized fats. On the other hand, secondary products of lipid autoxidation can be absorbed and may cause an increase in oxidative stress and deleterious changes in lipoprotein and platelet metabolism. The presence of reactive lipid oxidation products in foods needs more systematic research in terms of complexities of food component interactions and the metabolic processing of these compounds.

Oxygen-dissociation kinetics in the blood of smokers and non-smokers: interaction between oxygen and carbon monoxide at the hemoglobin molecule

The importance of smoking as a possible factor in coronary heart disease (CHD) may be related to the effect of carbon monoxide (CO) on oxygen exchange at the hemoglobin molecule (Hb). We examined the kinetics of this process in vitro and ex vivo using a fast-reaction technique (stopped-flow) whereby the dissociation-rate constant of oxygen was determined in the blood of smokers and non-smokers and at fixed HbCO-concentrations in non-smokers blood. In non-smokers, carbon monoxide saturated blood was obtained by gassing with carbon monoxide and mixing the samples with appropriate carbon monoxide free blood to achieve HbCO-concentration in the range of 10-60%. The reaction time course for the oxygen-dissociation was divided into a non-linear-initial phase (loss of the first oxygen molecule) and a subsequent linear phase. The oxygen-dissociation velocity decreased from 96.5 x 10(3) ms-1 to 42.7 x 10(3) ms-1 in the linear phase at pH 7.4 and decreased from 29.2 x 10(3) ms-1 to 20.9 x 10(3) ms-1 at pH 9.2 when the HbCO-concentration was increased to 63%. For the initial phase at pH 7.4, the dissociation velocity decreased depending on the HbCO-concentration. In non-smokers 50% of the bound oxygen was released in 17.5 +/- 2.3 ms (n = 13) whereas in smokers 19.4 +/- 1.8 ms (n = 14) (p less than 0.05) was required.(ABSTRACT TRUNCATED AT 250 WORDS)