Chronic carbon disulfide encephalopathy

Maternal residential exposure to solvents from industrial sources during pregnancy and childhood cancer risk in California

BACKGROUND

Maternal solvent exposure has been suspected to increase offspring cancer risk. The study aimed to evaluate the associations between maternal residential exposure to solvents from industrial pollution during pregnancy and childhood cancer.

METHODS

The present study included 15,744 cancer cases (aged 0-19 years at diagnosis) identified from California Cancer Registry and 283,141 controls randomly selected from California Birth Registry (20:1 frequency-matched by birth year: 1998-2016). We examined industrial releases of tetrachloroethylene and 1,1,1-trichloroethane within 3 km of the birth address, while we used a 5 km buffer for carbon disulfide. We calculated the total exposure from all linked Toxic Release Inventory sites during each index pregnancy and assigned "ever/never" and "high/low exposed/unexposed" exposure, using median values. We performed quadratic decay models to estimate cancer risks associated with maternal solvent exposure in pregnancy.

RESULTS

1,1,1-Trichloroethane was associated with rhabdomyosarcoma (adjusted Odds Ratio (aOR): 1.96; 95% Confidence Interval (CI): 1.16, 3.32) in the "ever exposed" group. Ever exposure to carbon disulfide was associated with increased risks of medulloblastoma (OR = 1.85, 95% CI 1.01, 3.40) and ependymoma (OR = 1.63, 95% CI 0.97, 2.74).

CONCLUSIONS

Overall, our findings suggested maternal residential exposure to solvents from industrial sources might be associated with elevated childhood cancer risks.

Occupational and domestic exposure associations with cerebral small vessel disease and vascular dementia: A systematic review and meta-analysis

INTRODUCTION

The prevalence of cerebral smallvessel disease (SVD) and vascular dementia according to workplace or domestic exposure to hazardous substances is unclear.

METHODS

We included studies assessing occupational and domestic hazards/at-risk occupations and SVD features. We pooled prevalence estimates using random-effects models where possible, or presented a narrative synthesis.

RESULTS

We included 85 studies (n = 47,743, mean age = 44·5 years). 52/85 reported poolable estimates. SVD prevalence in populations exposed to carbon monoxide was 81%(95% CI = 60-93%; n = 1373; results unchanged in meta-regression), carbon disulfide73% (95% CI = 54-87%; n = 131), 1,2-dichloroethane 88% (95% CI = 4-100%, n = 40), toluene 82% (95% CI = 3-100%, n = 64), high altitude 49% (95% CI = 38-60%; n = 164),and diving 24% (95% CI = 5-67%, n = 172). We narratively reviewed vascular dementia studies and contact sport, lead, military, pesticide, and solvent exposures as estimates were too few/varied to pool.

DISCUSSION

SVD and vascular dementia may be associated with occupational/domestic exposure to hazardous substances. CRD42021297800.

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.

Evaluating suspected work-related neurologic disorders (clinical diagnosis)

The clinical diagnosis of work-related neurologic disorders is essentially one of exclusion because symptoms and signs are often nonspecific. The clinical reasoning requires a three-step approach: (1) establish the characteristics of the presenting disease; (2) ascertain that observed clinical features are consistent with those caused by the suspected agent(s); and (3) assess occupational exposures. A detailed history is of paramount importance in evaluating patients with suspected work-related neurologic disorders as it is in other clinical contexts, especially because in some circumstances it may represent the only criterion to establish causality. Thus, besides characterization of neurologic symptoms, including their location, quality, timecourse, and possible other associated symptoms, the work environment of the patient should be understood in full detail. In this respect, when a neurotoxin is suspected, then the history collection can be guided by the knowledge of the likely syndromes it produces. Similarly, physical examination should be directed to the target of toxicity/entrapment based on information from the work history. Although specific sites and elements of the nervous system may be affected depending on the offending agent, most neurotoxic disorders are characterized by generalized rather than focal neurologic abnormalities. Laboratory toxicologic tests have limited application for the etiologic diagnosis of neurotoxic disorders, except in cases of acute poisoning and in patients exposed to neurotoxic chemicals with prolonged half-life. In most cases examination takes place after the end of exposure, when the offending chemical is no longer detectable in body fluids. Electrophysiologic studies, in particular evoked potentials, electromyography, and conduction velocities, are important to confirm the organic basis of symptoms, particularly to detect subclinical or early neurologic involvement and to reduce the number of disorders to be considered in the differential diagnoses. In general, imaging studies with computed tomography and magnetic resonance are of limited utility in the evaluation of suspected neurotoxic disorders, except for helping to exclude other causes of the patient's clinical state. Improved conditions and safer practices in the workplace have led to a gradual shift in application of neuropsychologic evaluation from the assessment of severe neurotoxic damage to the evaluation of mild subclinical disturbances, and these tests are nowadays extensively used in screening workers exposed to neurotoxicants. Tools used in the screening of large groups of workers exposed to neurotoxicants may differ from those used in the clinic. Whereas some are obviously impractical, such as physical examination, others, such as, for instance, toxicologic tests, are used for biologic monitoring of exposure to ascertain compliance with occupational exposure limits.

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.

Neurobehavioral and clinical effects in workers exposed to CS2

OBJECTIVES

Diffuse vascular encephalopathy, parkinsonism and peripheral polyneuropathy (PNP) due to CS(2) exposure are known since long. Data concerning low exposure are sparse. The current study aimed to evaluate whether the decrease of exposure below the threshold limit value (TLV) of 31 mg/m(3) results in an absence of neurological health effects using the same health outcomes as in the first study.

METHODS

The study was conducted in a group of workers of a viscose rayon plant and a control group (CG, n=66). The exposed group was divided into two groups, according to the average CS(2) exposure being below (EG1; n=60) or above 31 mg/m(3) (EG2; n=25). If the current TLV seemed insufficient to prevent effects, the analysis was repeated with three subgroups (10, >10 to 30, >30 mg/m(3)) to estimate the NOEL. Every participant filled in the neurotoxicity symptom checklist (NSC-60) and the Q16. Clinical neurological examination, computer-assisted neurobehavioral tests (NES) and neurophysiological examinations (nerve conduction velocities and electromyography (EMG)) were performed.

RESULTS

Sensorimotor complaints (NSC-60) were significantly worse in both EG1 and EG2 compared to CG (p=0.032) and both exposure groups had a higher proportion of positional tremor compared with CG (p=0.046). Finger tapping in the dominant and non-dominant hand (NES) was worse in EG1 and EG2 compared with CG (both p<0.001). A significant increase in sural nerve SCV, a significant decrease in sural nerve SNAP amplitude and duration and sympathetic skin response (SSR) amplitude, and higher prevalence of EMG abnormalities and PNP was also found in both EG1 and EG2 (p<0.003). All effects remained significant after controlling for possible confounding factors. Further analysis suggested that even average CS(2) exposures of 10 mg/m(3) could still cause effects on positional tremor, finger tapping dominant and non-dominant hand, sural nerve amplitude, SSR amplitude and EMG abnormalities.

CONCLUSIONS

An excess of psychomotor slowing, tremor and PNP was found in workers on average exposed to CS(2) concentrations below 31 mg/m(3). Data suggest that even average exposures as low as 10 mg/m(3) can cause the deleterious effects. This indicates that the current TLV insufficiently protects against neurological effects and, as a consequence, should be lowered.

Toxic Encephalopathies

Effective brain function is dependent on precise and complex interactions among neurotransmitters, hormones, enzymes, and electrolytes. Many of the chemically complex substances with which we come into contact can disrupt this intricately balanced system. Toxic substances, whether ingested, inhaled, or absorbed through the skin, may cause an encephalopathic state directly by affecting the brain itself or indirectly by compromising the brain's supportive systems. The article focuses on neurotoxins (heavy metals, solvents and vapors, pesticides, and natural neurotoxins) that directly induce an encephalopathic state.

Six year observational cohort study of the effect of carbon disulphide on brain MRI in rayon manufacturing workers

AIMS

To clarify whether the current occupational exposure limit (OEL) for carbon disulphide (CS2) is low enough to prevent the occurrence of adverse effects on the cerebrovascular system.

METHODS

A total of 432 male workers exposed to CS2 and 402 male referent workers in 11 Japanese viscose rayon factories were studied at baseline; 750 of these were followed up. Brain MRI was performed at both baseline and follow up surveys. Changes in the number of hyperintense spots in T2 weighted images (HIS), which point to so-called "silent cerebral infarctions", were evaluated over six years. A total of 666 subjects (217 exposed, 125 ex-exposed, and 324 referent subjects) who twice received brain MRI were subjected to analysis. Mean duration of exposure to the end of the study was 19.6 years for the exposed workers. The geometric mean CS2 (ppm) and TTCA (mg/g creatinine) concentrations for the past six years were 4.9 and 1.6 for all exposed workers, 5.8 and 1.9 for spinning/refining workers, and 2.7 and 0.9 for other exposed workers, respectively.

RESULTS

Exposed subjects showed a significantly higher risk for an increase in the number of HIS over six years. Odds ratios adjusted for possible confounders in the exposed and ex-exposed workers were 2.27 (95% CI 1.37 to 3.76) and 1.33 (95% CI 0.70 to 2.54), respectively. No exposure-response relations were observed in a number of analyses among the exposed workers.

CONCLUSIONS

Exposure to CS2 under the current Japanese OEL, 10 ppm, might increase the number of HIS in brain MRI. However, results should be interpreted with caution.

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.

Long-term neuropsychological effects and MRI findings in patients with CS2 poisoning

OBJECTIVES

To evaluate the long-term neuropsychological effects and magnetic resonance imaging (MRI) findings among retired patients with a history of exposure to carbon disulfide (CS2).

MATERIAL AND METHODS

Seventy-four patients with a history of exposure to CS2 were divided into two equal groups according to their level of exposure, and they completed a questionnaire and were evaluated for neuropsychological symptoms using the Korean version of the revised Wechsler Adult Intelligence Scale. Thirty-one MRI images were reviewed retrospectively.

RESULTS

There were no statistically significant differences in total, verbal and performance IQs between high- and low-exposure groups. MRI findings revealed a significantly larger number of cerebral lacunae (five of 12 subjects) in the high-exposure group. Periventricular hyperintensities were mostly located in frontal and occipital areas, and white-matter hyperintensities were mostly in frontal and parietal areas.

CONCLUSION

The higher prevalence of lacunae in the high-exposure group as revealed by MRI suggests that further MRI studies are needed into long-term neuropsychological effects induced by CS2.

Chemicals and gases

This article covers the major chemicals and gases that are considered to be of the most clinical relevance to the primary care provider. The reader is referred to other comprehensive textbooks of toxicology and occupational medicine for a complete discussion of the numerous additional products found in the workplace that may result in occupational exposure.