A six year follow up study of the subclinical effects of carbon disulphide exposure on the cardiovascular system

Carbon disulfide exposure induced lung function reduction partly through oxidative protein damage: A cross-sectional and longitudinal analysis

Carbon disulfide (CS₂) exposure has been associated with lung function reduction in occupational population. However, evidence on the general population with relatively low CS₂ exposure is lacking and the mechanism involved remains largely unknown. Urinary CS₂ metabolite (2-mercaptothiazolidine-4-carboxylic acid, TTCA) and lung function were determined in the urban adults from the Wuhan-Zhuhai cohort at baseline in 2011-2012 and were repeated every 3 years. Cross-sectional and longitudinal associations between TTCA and lung function were estimated using linear mixed models. Inflammation and oxidative damage biomarkers in blood/urine were measured to evaluate their potential mediating roles involved. Cross-sectionally, participants in the highest quartile of TTCA level showed a 0.64% reduction in FEV₁/FVC and a -308.22 mL/s reduction in PEF, compared to those in the lowest quartile. Longitudinally, participants with consistently high TTCA level had annually -90.27 mL/s decline in PEF, compared to those with consistently low TTCA level. Mediation analysis revealed that plasma protein carbonyl mediated 49.89% and 22.10% of TTCA-associated FEV₁/FVC and PEF reductions, respectively. Conclusively, there was a cross-sectional and longitudinal association between CS₂ exposure and lung function reduction in the general urban adults, and protein carbonylation (oxidative protein damage) partly mediated lung function reduction from CS₂ exposure.

Environmental monitoring and health assessment in an industrial town in central India: A cross-sectional study protocol

Background

Textile industry has been widely implicated in environmental pollution. The health effects of residing near manufacturing industries are not well documented in India, especially in central India. Hence, a cross-sectional environmental monitoring and health assessment study was initiated as per directions of the local authorities.

Methods

Comprehensive exposure data about the concentrations of relevant pollutants in the ambient air and ground water samples in the study area will be collected over one year. Using stratified random sampling, 3003 apparently healthy adults will be selected from the study area. Sociodemographic and anthropometric information, relevant medical and family history, and investigations including spirometry, electrocardiogram, neurobehavioral tests, and laboratory investigations (complete blood count, lipid profile and random blood glucose) will be conducted. Finally Iodine azide test and heavy metal level detection in urine and blood samples respectively will be conducted in a subset of selected participants to assess individual pollution exposure. Ethics approval has been obtained from the Institutional Ethics Committee of the National Institute for Research in Environmental Health (No: NIREH/IEC-7-II/1027, dated 07/01/2021).

Discussion

This manuscript describes the protocol for a multi-disciplinary study that aims to conduct environmental monitoring and health assessment in residential areas near viscose rayon and associated chemical manufacturing industries. Although India is the second largest manufacturer of rayon, next only to China, and viscose rayon manufacturing has been documented to be a source of multiple toxic pollutants, there is a lack of comprehensive information about the health effects of residing near such manufacturing units in India. Therefore implementing this study protocol will aid in filling in this knowledge gap.

Carbon disulfide exposure estimate and prevalence of chronic diseases after carbon disulfide poisoning-related occupational diseases

Background

In Korea, Carbon disulfide (CS₂) toxicity was an important social problem from the late 1980s to the early 1990s but there have been few large-scale studies examining the prevalence of diseases after CS₂ exposure discontinuance. So we investigated past working exposure to CS₂ characteristics from surviving ex-workers of a rayon manufacturing plant including cumulative CS₂ exposure index. Furthermore, we studied the prevalence of their chronic diseases recently after many years.

Methods

We interviewed 633 ex-workers identified as CS₂ poisoning-related occupational diseases to determine demographic and occupational characteristics and reviewed their medical records. The work environment measurement data from 1992 was used as a reference. Based on the interviews and foreign measurement documents, weights were assigned to the reference concentrations followed by calculation of individual exposure index, the sum of the portion of each time period multiplied by the concentrations of CS₂ during that period.

Results

The cumulative exposure index was 128.2 ppm on average. Workers from the spinning, electrical equipment repair, and motor repair departments were exposed to high concentrations of ≥10 ppm. Workers from the maintenance of the ejector, manufacturing of CS_2, post-process, refining, maintenance and manufacturing of viscose departments were exposed to low concentrations below 10 ppm. The prevalence for hypertension, coronary artery disease, cerebrovascular disease, diabetes, arrhythmia, psychoneurotic disorder, disorders of the nervous system and sensory organ were 69.2%, 13.9%, 24.8%, 24.5%, 1.3%, 65.7%, 72.4% respectively.

Conclusions

We estimated the individual cumulative CS₂ exposure based on interviews and foreign measurement documents, and work environment measurement data. Comparing the work environment measurement data from 1992, these values were similar to them. After identified as CS₂ poisoning, there are subjects over 70 years of average age with disorders of the nervous system and sensory organs, hypertension, psychoneurotic disorder, cerebrovascular disease, diabetes, coronary artery disease, and arrhythmia. Because among ex-workers of the rayon manufacturing plant, only 633 survivors recognized as CS₂ poisoning were studied, the others not identified as CS₂ poisoning should also be investigated in the future.

Changes of median nerve conduction velocity in rayon manufacturing workers: A 6-year cohort study

Objectives:

We conducted a 6-year cohort study to evaluate the relationship between carbon disulfide (CS₂) exposure and reductions in the motor and sensory nerve conduction velocity (MCV and SCV) of the median nerve.

Methods:

Study subjects at baseline included 432 exposed workers and 402 unexposed workers. Among the exposed workers, 145 workers terminated CS₂ exposure during the follow-up period (ex-exposed workers). MCV and SCV were measured at baseline and followed up. CS₂ personal exposure concentration was measured two times a year during a 6-year follow-up period and mean (range) CS₂ exposure concentrations (ppm) were 5.96 (0.8-16.0) and 3.93 (0.6-9.9) in the exposed and ex-exposed workers, respectively.

Results:

Reductions in MCV during the follow-up period did not differ among the exposed, ex-exposed, and unexposed workers. Reduction in SCV (m/s) of the exposed workers (-4.47±3.94) was significantly larger than that of the unexposed (-3.38±3.97) and ex-exposed workers (-3.26±3.79). For SCV reduction, a partial multiple regression coefficient of (ex-exposed workers) / (unexposed workers) was significantly positive (+0.915, p < 0.01) after adjustment for confounding variables.

Conclusions:

This cohort study showed that 6-year CS₂ exposure around a mean level of 6 ppm did not affect MCV reduction but induced significant SCV reduction beyond the influence of aging. The effect of CS₂ on SCV around a mean exposure level of 4 ppm may be reversible, since it disappeared in the ex-exposed workers after CS₂ exposure cessation for a mean period of 4.1 years.

[Epidemiologic review of long-term, low-level exposure to environmental chemicals and cardiovascular disease: an exposure-response relationship]

The effects of exposure to environmental chemicals, such as heavy metals and fine particulates, on cardiovascular diseases have been reported. To set a permissible exposure standard, an exposure-response relationship should be elucidated. Thus, epidemiologic evidence in relation to long-term, low-level exposure to environmental chemicals (i.e., lead, cadmium, mercury, arsenic, PM(2.5), carbon disulfide) was reviewed. As a result, there exists a clear exposure-response relationship between exposure to lead or PM(2.5) and cardiovascular diseases, but those cohort studies were carried out in the US only. From epidemiologic viewpoint, "consistency" of the observed relationship must be clarified, especially findings of a study in the Japanese population. It is well known that the distribution pattern of cardiovascular risk factors are quite different between two countries, which could modify the true relationship. This will require studies of large samples from the general Japanese population with control for potential confouders. Moreover, to detect a small effect of exposure within low-level range, random misclassification of exposure as well as that of effect must be minimized. Thus, for studies of heavy metals, sensitive biomarkers identified in toxicological studies would be applied. For PM(2.5), a wide range of population samples should be covered by a national sampling network in the near future. Finally, the integration of epidemiologic and toxicological evidence would be more important for risk assessment of environmental chemicals at low exposure levels, because an exposure-response relationship from only epidemiologic observation may be unstable with a wide confidence interval around the threshold.

The effects of carbon disulfide and ethanol on the circulatory system of rats

Carbon disulfide exerted adverse effects on the structure or hemodynamics of the cardiovascular system, and whether ethanol exposure modifies the cardiovascular effect of carbon disulfide, was examined. Male Sprague-Dawley rats were used in the study. Animals in the control and ethanol groups drank water containing 5% sugar, or 10% ethanol in addition to 5% sugar, respectively, for 14 wk. Sepatare animals inhaled 700 mg/m3 of carbon disulfide for 6 h daily. Carbon disulfide treatment did not affect the food and fluid consumption of the animals, while this gas decreased body mass gain. CS2 increased arterial blood pressure and cardiac index, decreased their cardiac output, the fraction of the cardiac output, and blood flow for the kidneys and the lungs, and increased the relative heart, liver, and kidneys mass and the vascular resistance of the brain, lungs, and kidneys. Ethanol decreased the food and fluid consumption and body mass gain of the animals, the fraction of the cardiac output for the kidneys, and the vascular resistance of the liver, while it increased the blood flow of the brain and liver. Simultaneous administration of carbon disulfide and ethanol decreased the heart rate and increased the QRS duration. Significant interaction was found between the effect in case of heart rate, PQ distance, and QRS duration; carbon disulfide significantly increased the minimal-moderate effect of ethanol on all three parameters. With histological examinations no pathologic alterations were found in the organs studied. It was concluded that the early hemodynamic changes produced by carbon disulfide may play a significant role in the pathomechanism of the effects of the substance (hypertension, damage to the myocardium and kidneys). On the other hand, a potentiating interaction of carbon disulfide was expected with the effects of ethanol, at the administered concentration and dose in the study.