N-hexane neuropathy in offset printers

[Neuropathy in n-hexane poisoning]

N-Hexane is a solvent widely used in manufacturing as a cleaner, degreaser and component of rubber cement. Chronic exposure to n-hexane either through contact with unprotected skin or inhalation can lead to the development of clinical symptoms and electrophysiological changes similar to those of inflammatory demyelinating polyneuropathy which requires careful differential diagnosis. This article presents three cases of severe predominantly motor polyneuropathy with demyelinating features in 15- and 16-year-old adolescents. The results of laboratory tests were within normal limits; electroneuromyography revealed symmetrical involvement of sensory and motor fibers of the nerves of the legs and arms with a decrease in the speed of propagation of excitation and conduction blocks. Sural nerve biopsy revealed intraneural and perineural swelling without any signs of inflammation or fibrosis confirming the genesis of the neuropathy. Despite a relatively favorable prognosis there is no specific therapy for hexane poisoning and the recovery period can last up to several years.

Acceptable Limits for n-Hexane in Spacecraft Atmospheres

INTRODUCTION:The Spacecraft Maximum Allowable Concentrations (SMACs) for C2-C9 alkanes set by NASA in 2008 under the guidance and approval of the National Research Council specifically excluded SMACs for n-hexane. Unlike other C2-C9 alkanes, n-hexane can cause polyneuropathy after metabolism in humans or rodents and so requires more stringent SMACs than the other members of this group do. This document reviews the relevant published studies of n-hexane toxicity to develop exposure duration-specific SMACs for n-hexane of 200 ppm for 1 hour, 30 ppm for 24 hours, and 2.4 ppm for 7 days, 30 days, 180 days, and 1000 days.Garcia HD. Acceptable limits for n-hexane in spacecraft atmospheres. Aerosp Med Hum Perform. 2021; 92(12):956-961.

The Role of Protein Adduction in Toxic Neuropathies of Exogenous and Endogenous Origin

The peripheral (axonal) neuropathy associated with repeated exposure to aliphatic and aromatic solvents that form protein-reactive γ-diketones shares some clinical and neuropathological features with certain metabolic neuropathies, including type-II diabetic neuropathy and uremic neuropathy, and with the largely sub-clinical nerve damage associated with old age. These conditions may be linked by metabolites that adduct and cross-link neuroproteins required for the maintenance of axonal transport and nerve fiber integrity in the peripheral and central nervous system.

Effect of environmental toxicants on neuronal functions

In the last few years, neurodegenerative diseases like Alzheimer's disease (AD) and Parkinson's disease (PD) have attracted attention due to their high prevalence worldwide. Environmental factors may be one of the biggest reasons for these diseases related to neuronal dysfunctions. Most of neuronal disorders are strongly associated with pre- and postnatal exposure to environmental toxins released from industries. Some of the neurotoxic metals such as lead, aluminum, mercury, manganese, cadmium, and arsenic as well as some pesticides and metal-based nanoparticles have been involved in AD and PD due to their ability to produce senile/amyloid plaques and NFTs which are the main feature of these neuronal dysfunctions. Exposure to solvents is also majorly responsible for neurodegenerative disorders. The present review highlights the impact of omnipresent heavy metals with some other neurotoxins on human health and how they give rise to neuronal dysfunctions which in turn causes socio-economic consequences due to increasing pollution worldwide. Graphical abstract.

Neuroprotein Targets of γ-Diketone Metabolites of Aliphatic and Aromatic Solvents That Induce Central-Peripheral Axonopathy

Peripheral neuropathy associated with chronic occupational and deliberate overexposure to neurotoxic organic solvents results from axonal degeneration in the central and peripheral nervous system. Human and experimental studies show that axonopathy is triggered by the action of neuroprotein-reactive γ-diketone metabolites formed from exposure to certain aliphatic solvents (n-hexane, 2-hexanone) and aromatic compounds (1,2-diethylbenzene, 1,2-4-triethylbenzene, 6-acetyl-1,1,4,4-tetramethyl-7-ethyl-1,2,3,4-tetralin). Neuroprotein susceptibility is related primarily to their differential content of lysine, the ∊-amino group of which is targeted by γ-diketones. Specific neuroprotein targets have been identified, and the sequence of molecular mechanisms leading to axonal pathology has been illuminated. While occupational n-hexane neuropathy continues to be reported, lessons learned from its experimental study may have relevance to other causes of peripheral neuropathy, including those associated with aging and diabetes mellitus.

No-observed-adverse-effect level of hair pyrrole adducts in chronic n-hexane intoxication in rats

n-Hexane has been reported to induce serious peripheral neuropathy in workers. Pyrrole adducts are the unique reaction products of n-hexane in organisms and have been demonstrated to be critical to n-hexane neuropathy. Our previous studies have demonstrated that pyrrole adducts could accumulate in hair and showed high correlation with neuropathy at the end of experiments in rat models. In the present study, we examined the time course of hair pyrrole adducts and behavioral changes in rats exposed to different dosages of n-hexane in both treatment (24 weeks) and recovery phases. Our results showed: 1. After treatment, 1.0, 2.0, and 4.0 g/kg dosage groups all lost weight, but the 0.5 g/kg dosage group showed no impairment; after recovery, all impaired rats regained weight. 2. After treatment, 1.0, 2.0, and 4.0 g/kg dosage groups all showed a rise in gait scores, decreased rotarod latency, and decreased motor nerve conduction velocity, whereas the 0.5 g/kg dosage group showed no impairment; after recovery, all impaired rats were completely rehabilitated. 3. After treatment, levels of pyrrole adducts in serum, urine, and hair of experimental groups increased; after recovery, serum and urine pyrrole adducts showed no difference from the control (P > 0.05), whereas hair pyrrole adducts were significantly different from the control (P < 0.01). 4. The half-lives of serum and urine pyrrole adducts were 47.8-78.0 h and 42.7-52.9 h, while the half-life of hair pyrrole adducts was 14-24 weeks. 5. During treatment and recovery, levels of serum, urine, and hair pyrrole adducts showed high correlation with gait scores (P < 0.01), and hair pyrrole adducts had the largest partial correlation coefficient. In conclusion, hair pyrrole adducts could serve as a stable and reliable biomarker for the prevention of n-hexane intoxication. Furthermore, the no-observed-adverse-effect level of hair pyrrole adducts in rats is 275.2 ± 61.5 nmol/g protein. Further studies are required for the definition of the biological exposure limit in humans.

Diallyl sulfide-induced attenuation of n-hexane-induced peripheral nerve impairment is associated with metabolic inhibition of n-hexane

Chronic exposure to n-hexane could induced serious peripheral nerve impairments. It has been well documented that the metabolic activation from n-hexane to 2,5-hexanedione (2,5-HD) is vital in the pathogenesis. Diallyl sulfide (DAS) is an extract of garlic and able to block the bioactivation of xenobiotic. The current study was designed to investigate whether DAS can attenuate n-hexane induced neuropathy. Male Wistar rats were pretreated with DAS (50 or 100 mg/kg.bw) and then n-hexane (3 g/kg.bw) for 7 weeks. Behavioral performance, biomarker measurement and toxicokinetic studies were performed. Enzymatic methods and western blotting analyses were also conducted to investigate the hepatic phase I enzymes (including cytochrome P450(CYP)2E1, CYP1A1 and CYP2B1) and phase II enzymes (including glutathione S transferase theta 1 (GSTT1) and NA(D)PH dehydrogenase quinone 1 (NQO1)). The results showed that DAS improved the behavioral performance while reducing the toxic metabolite: 2,5-HD and pyrrole adducts. Besides, DAS reduced the expression of CYP2E1 with a proportional decrease in activity, which largely decreased the bioactivation of n-hexane in vivo. The results suggested that DAS decreased the toxic metabolites of n-hexane to attenuate n-hexane-induced peripheral neuropathy.

Hexane exposure and persistent peripheral neuropathy in automotive technicians

Automotive technicians are commonly exposed to organic and chlorinated solvents, particularly through use of cleaning products. Mainly during the period 1989-2002, n-hexane was a component of some of these products. In other occupational contexts, n-hexane has been shown to be a cause of peripheral neuropathy. The purpose of the present study was to investigate whether previous exposures to low concentrations of n-hexane were a cause of persistent peripheral neuropathy in automotive technicians. Enrolled in the study were 830 San Francisco Bay Area automotive technicians. Each participant underwent a battery of tests to investigate peripheral nervous system impairment. Test results regressed against estimated hexane and total solvent exposures showed only limited evidence of association with solvent exposures. Exposures to both hexane and general solvents were well below their occupational exposure limits. Generally, our results provide reassurance about persistent peripheral neuropathic effects in automotive technicians who previously used hexane-containing automotive cleaning products. This may reflect repair processes, since the exposures occurred some years previous to the study. However, we cannot exclude the possibility that the absence of observed effect in this study may be attributable to low exposures, exposure misclassification and/or the healthy worker survivor effect.

Hong Kong Poison Information Centre: Annual Report 2010

Objective

To report and analyse the poisoning data of Hong Kong Poison Information Centre (HKPIC) in 2010.

Methods

In 2010, all poisoning cases received by HKPIC were retrieved from its database (PICMS) for analysis.

Results

A total of 4,418 poisoned cases were analysed. There were 1,863 male patients (42.2%) and 2,540 female patients (57.5%). More than two-third of cases (68.3%) were between 20 and 59 years old. Common causes of exposure were suspected self harm/suicidal attempt, unintentional exposure and abusive use. Benzodiazepine, paracetamol, ketamine, zopiclone, and Chinese herbal medicine were the common agents involved. Majority of the patients were managed supportively, with 10.2% and 9.7% treated by decontamination and antidotes respectively. Most cases had uneventful recovery; 1.0% of the poison exposure resulted in death and 5.3% of the exposure had major outcomes.

Conclusions

This fifth annual report provides updated epidemiological information on poisoning pattern in Hong Kong and emphasized some changes in comparing with our previous reports.

n-Hexane intoxication in a Chinese medicine pharmaceutical plant: a case report

BACKGROUND

n-Hexane is a well-known neurotoxicant. Polyneuropathy due to occupational n-hexane exposure has been reported worldwide, however, our case is the first report in the Chinese herb industry.

CASE PRESENTATION

A 25-year-old Asian man experienced progressive weakness and numbness in his hands and feet after working as an operator in a Chinese medicine pharmaceutical plant for the manufacture of Chinese herbal pain relief patches for 10 months. Electrophysiological studies indicated a reduction in nerve conduction velocity, prolongation of distal latencies, mildly positive sharp waves, and reduced recruitment with polyphasic potentials, particularly at distal sites. Demyelination with axonal degeneration caused by occupational n-hexane exposure was strongly suspected. Through investigation of our patient's workplace, the ambient n-hexane concentration in air was found to considerably exceed the permissible exposure limit/time-weighted average for n-hexane in Taiwan. His symptoms were gradually relieved after 4 months of cessation of exposure to n-hexane. He was then confirmed as a case of occupational n-hexane intoxication. Further effective control measures should be implemented as soon as possible to prevent exposure of workers to n-hexane.

CONCLUSIONS

Despite a typical clinical presentation, his exposure at workplace was appropriately investigated. Chemical exposure in Chinese medicine pharmaceutical plants could be an emerging issue that may affect workers' health. The lack of knowledge and management of solvents could endanger the health of workers. This case has profound educational implications for occupational health and is worthy of further follow-up for improving hazards control.

Reversible cerebral and brain stem dysfunction in n: Hexane neuropathy

A 18-year-old male, screen printer by profession developed sensory motor polyneuropathy, change in his behavior, bilateral 6^th and 7^th cranial nerve palsies, down beat nystagmus and cerebellar dysarthria. He had bilaterally prolonged P100 latency; left: 137 ms; right: 144 ms. P 37 was not recordable on either side while N 20 was normal. The inter latency difference between Ipsilateral R2 and Contralateral R2 was 6.15 ms, on the left side and normal on the right side. In the follow-up, there was normalization of the blink reflex study, improvement in P100 latency [left: 114 ms; right: 120 ms.] but worsening of peripheral nerve conductions. The sequential clinical recovery was of the behavioral dysfunction, down beat nystagmus, 6^th nerve, 7^th nerve involvement and ataxia, in that order. Sural nerve biopsy showed loss of large diameter myelinated fibers.

Quality of Chemical Safety Information in Printing Industry

OBJECTIVES

Employees in printing industries can be exposed to multiple solvents in their work environment. The objectives of this study were to investigate the critical components of chemical solvents by analyzing the components of the solvents and collecting the Safety data sheets (SDSs), and to evaluate the hazard communication implementation status in printing industries.

METHOD

About 152 printing-related industries were recruited by area-stratified random sampling and included 23 plate-making, 102 printing and 27 printing-assistance companies in Taiwan. We analyzed company questionnaires (n = 152), SDSs (n = 180), and solvents (n = 20) collected from this sample of printing-related companies.

RESULTS

Analytical results indicated that benzene and ethylbenzene, which were carcinogen and possibly carcinogen, were detectable in the cleaning solvents, and the detection rate were 54.5% (concentrations: <0.011-0.035 wt%) and 63.6% (concentrations: <0.011-6.22 wt%), respectively; however, neither compound was disclosed in the SDS for the solvents. Several other undisclosed components, including methanol, isopropanol and n-butanol, were also identified in the printing inks, fountain solutions and dilution solvents. We noted that, of the companies we surveyed, only 57.2% had a hazard communication program, 61.8% had SDSs on file and 59.9% provided employee safety and health training. We note that hazard communication programs were missing or ineffective in almost half of the 152 printing industries surveyed.

CONCLUSIONS

Current safety information of solvents components in printing industries was inadequate, and many hazardous compounds were undisclosed in the SDSs of the solvents or the labels of the containers. The implementation of hazard communications in printing industries was still not enough for protecting the employees' safety and health.

Clinical description of toxic neuropathies

Toxic neuropathy, although rare, is an important consideration in the setting of a known or suspected toxic exposure in the workplace or other environment. This chapter discusses the clinical and electrodiagnostic evaluation of peripheral neuropathies, highlighting findings that direct further workup and may point to specific toxins as etiology. The difficulty of establishing causality of a toxin in relation to peripheral neuropathy is discussed; guidelines for establishing causality are presented. Examples of common industrial toxins are listed, including their typical industrial uses and their mechanisms of action in producing neuropathy. Characteristic clinical presentations of specific toxic neuropathies are highlighted with selected case studies.

A novel and highly sensitive gaseous n-hexane sensor based on thermal desorption/cataluminescence

A novel and highly sensitive sensor for gaseous n-hexane utilizing the sensing material Y₂O₃–Al₂O₃ has been developed based on thermal desorption/cataluminescence (TD/CTL) combined with response surface methodology (RSM).

Diagnosis and management of pediatric peripheral neuropathies in resource-poor settings

The diagnosis of a peripheral neuropathy in a child who resides in the majority of resource-poor settings is based on the history taken and the clinical examination. The majority of children, unless they demonstrate additional clinical markers, will lack a more definitive diagnosis beyond the label ‘peripheral neuropathy’. The treatable, typically acquired conditions, which are prevalent in these settings, are the priority to identify. This would include neuroinfections, neuroinflammation, toxins and vitamin deficiencies. The management of children with peripheral neuropathies in resource-poor settings must be approached in a different manner to that of more ‘resource-equipped’ settings. Secondary or tertiary centers are scarce, often significant distances away from the patient, and this leads to long delays before access is possible. Most children present to primary healthcare settings and are seen by practitioners with little training in the features suggestive of a peripheral neuropathy. As such, basic aids to assist the healthcare worker in the early recognition and interventions of a child with a peripheral neuropathy are important. In addition, there must be recognition of the child with a rapidly progressive neuropathy where a life-threatening condition is present, and urgent referral to a tertiary setting made wherever possible.

Polymorphisms of GSTT1, GSTM1, and EPHX genotypes in patients with cryptogenic polyneuropathy: a case-control study

The aim of this study was to analyze whether polymorphisms for the null alleles of Glutathione S-Transferase Mu-1 (GSTM1), Glutathione S-Transferase Theta-1 (GSTT1), and a low-activity genetic variation of epoxide hydrolase exon three (EPHX*3) affect the risk of developing polyneuropathy. The enzymes of these genes are important in the metabolism of toxic compounds. Seventy-nine patients with cryptogenic polyneuropathy (equivalent to chronic idiopathic axonal neuropathy) and 398 controls were tested for the genetic polymorphism. Medical records were reviewed to collect data regarding clinical findings at diagnosis, and exposure data was collected via questionnaires. The odds ratios (ORs) for the null forms of GSTM1 and GSTT1 and the normal activity YY form of EPHX*3 were close to one except GSTT1, which reached 1.86. The highest risk of polyneuropathy was found in smokers with GSTT1 null, who had a 3.7 times increased risk. Interactions between genes were analyzed and confirmed the increased OR for GSTT1, which was strongest if the patients had the low-activity HH form of EPHX*3 (OR 2.37). Our hypothesis is that the GSTT1 null polymorphism may be related to an impaired metabolism of toxic substances that could lead to nerve damage in the peripheral nervous system.

Implementing safer alternatives to lithographic cleanup solvents to protect the health of workers and the environment

The use of volatile organic compounds (VOCs) in lithographic printing cleanup is an environmental and occupational hazard. Regulations to reduce ambient ozone levels limited VOC emissions from lithographic cleanup operations and spurred the development of low-VOC alternatives. The purpose of this project was to promote the substitution of hazardous cleanup solvents with less toxic chemicals to protect the health of workers and the environment. A convenience sample of printers, employers, union, industry, and government representatives was constructed. Data regarding the lithographic printing work force and the use of cleanup solvents and alternatives were collected through: (1) work site walk-throughs, (2) a focus group, (3) key informant interviews, (4) a half-day workshop, and (5) demonstration projects. Overall, 66 individuals from 15 different print shops, 10 government agencies, the lithographic printing industry, and one printer's union participated in one or more aspects of the project. Printer inhalation exposure to hazardous cleanup solvents was prevalent and printers were not aware of safer alternatives. Employers should implement low-VOC, low-toxicity cleanup products in a timely manner to protect the health of printers and the environment. Use of low-VOC lithographic cleanup products does not mitigate the potential for printer dermal exposure and may carry safety and ergonomic implications. Lithographic cleanup solvent manufacturers should seek low-VOC ingredients that do not pose a dermal exposure hazard. Linking environmental and occupational health prevented the development of substitutes that would have introduced worker hazards and provided an opportunity to circumvent some of the inadequacies of the current occupational health regulatory apparatus. Governmental organizations should establish and maintain institutional interdisciplinary mechanisms to support these linkages.

Association between metabolic gene polymorphisms and susceptibility to peripheral nerve damage in workers exposed ton-hexane: A preliminary study

Chronic exposure to n-hexane may result in peripheral neuropathy. 2,5-Hexanedione (2,5-HD) has been identified as a toxic metabolite of n-hexane. The CYP2E1, CYP1A1 and GST genes are involved in the formation of 2,5-hexanedione from n-hexane as well as the elimination of 2,5-HD-formed electrophile, and these genes are highly polymorphic in the general population. A nested case-control study in an industrial cohort was conducted to evaluate the associations between polymorphisms in these metabolic genes and n-hexane-induced peripheral nerve damage. The study subjects included 22 cases, who worked in a printing factory with symptoms of peripheral nerve damage, and 163 controls, who came from the same factory of cases. DNA was extracted from blood samples and genotyping was conducted for CYP2E1 Pst, CYP2E1 Dra, CYP2E1 Ins96, CYP1A1 Msp, GSTT1 null, GSTM1 null and GSTP1 105V. Unconditional logistic regression was applied to estimate the odds ratio and 95% confidence intervals. There were no significant differences between the two groups regarding age, sex, smoking and alcohol status. A significant association between Dra polymorphism and peripheral nerve damage was found. The frequency of CYP2E1 Dra homozygous mutation in the case group (18.2%) was higher than that in the control group (3.7%, p=0.015). Individuals with homozygote genotype (CC) of CYP2E1 Dra had a significantly higher risk of peripheral nerve damage compared with those with DD genotype (adjusted OR=?.58, 95% CI=1.32-23.65) after n-hexane exposure duration, sex, age, smoking and alcohol status were adjusted. No significant association was found that CYP2E1 Pst, CYP2E1 Ins96, CYP1A1 Msp, GSTT1, GSTM1, GSTP gene polymorphisms associated with the susceptibility of peripheral nerve damage. These findings suggested that CYP2E1 gene might increase the susceptibility to n-hexane-induced peripheral damage.

Toxic neuropathies associated with pharmaceutic and industrial agents

Neuropathies associated with industrial, environmental, and pharmacologic toxicants are uncommon. Nevertheless, it is important to consider toxic etiologies in the differential diagnosis of neuropathies, because they are among the most treatable forms of peripheral nervous system dysfunction. The purpose of this article is to discuss the clinical investigation of a suspected toxic neuropathy, to review some of the more common or representative neurotoxicants, and to identify the methods for establishing causation.

Worker exposure to volatile organic compounds in the vehicle repair industry

This study evaluated exposures among vehicle repair technicians to hexane, acetone, toluene, and total volatile organic compounds (VOCs). On randomly selected workdays, we observed a characteristic pattern of solvent use among 36 technicians employed in 10 repair shops, each of which used an aerosol solvent product. We obtained quantitative exposure measurements from a subset of nine technicians (employed in three of these shops) who used an aerosol product containing hexane (25-35%), acetone (45-55%), and toluene (5-10%). The time-weighted average (TWA) exposure concentration for task-length breathing zone (BZ) samples (n = 23) was 36 mg/m(3) for hexane, 50 mg/m(3) for acetone, and 10 mg/m(3) for toluene. The TWA area concentrations (n = 49) obtained contemporaneously with BZ samples ranged from 25% to 35% of the BZ concentrations. The solvent emission rate (grams emitted/task time) was correlated with the total VOC exposure concentration (R(2) = 0.45). The proportions of VOCs in the BZ samples were highly correlated (r = 0.89 to 0.95) and were similar to those of the bulk product. Continuous exposure measurements for total VOCs (n = 1238) during 26 tasks produced a mean BZ VOC "pulse" of 394 mg/m(3) within 1 min following initiation of solvent spraying. The geometric mean air speed was 5.2 meters/min in the work areas (n = 870) and was associated with 0.8 air changes per minute in the BZ. The findings suggest that vehicle repair technicians who use aerosol solvent products experience episodic, inhalation exposures to the VOCs contained in these products, and the proportions of VOCs in the breathing zone are similar to those of the bulk product. Because acetone appears to amplify the severity and duration of the neurotoxic effects of n-hexane, products formulated with both hexane and acetone should be avoided. Further evaluation of exposures to VOCs is needed in this industry, along with information on effective alternatives to aerosol solvent products.

Knowledge, attitude and practice regarding organic solvents among printing workers in Hong Kong

To find out the prevalence of good knowledge, appropriate attitude and safe practice among printing workers exposed to organic solvents in Hong Kong, and to see if safe practice was influenced by the knowledge of and the attitude towards the harmful effects of organic solvents as well as other factors. The survey was conducted in a sample of 501 male printing workers from 28 factories in Hong Kong. The knowledge of and attitude towards the harmful effects of organic solvents, as well as the good practices adopted by the workers when handling solvents were explored using a questionnaire. Multiple logistic regression analysis was conducted to identify the major factors that influenced the knowledge, attitude and practice of workers. The prevalence of good knowledge, appropriate attitude and safe practice was low, being 20.4%, 38.4% and 22.0% respectively. Good knowledge was positively associated with awareness of the relevant legislation and past drinking behavior and negatively associated with current smoking. Appropriate attitude depended on having good knowledge and younger age. Safe practice did not depend on knowledge and attitude, but was positively associated with being informed of safety precautions and being supplied with chemical information by supervisors. The majority of workers believed that their employers, the Government and other statutory bodies should be responsible for providing information on chemicals, but very few of them actually obtained information from these sources. More workers preferred publications and talks rather than television as the means of obtaining further knowledge on chemicals. Front line supervisors have a pivotal role to play in improving safe practices of workers by informing them of the necessary precautions and supplying the relevant chemical information.

Occupational exposure to mixtures of organic solvents increases the risk of neurological symptoms among printing workers in Hong Kong

LEARNING OBJECTIVES

Summarize the nature and extent of exposure to organic solvents to which printing workers in this study were subjected. Compare the numbers of neurological symptoms in exposed and non-exposed workers and how they related to level of exposure, as defined by specific job title or by air sampling. Clarify the relationship between exposure to organic solvents and individual psychoneurological and other symptoms.

ABSTRACT

The health effects of low-dose occupational exposure to organic solvents remains unclear. A cross-sectional survey was conducted among 762 male printing workers to assess the impacts of exposure to mixtures of n-hexane, toluene, isopropyl alcohol, and benzene on neurological and other symptoms. After controlling for age, smoking, alcohol drinking, past exposure history, working hours and shift work, current exposure to solvent mixtures was significantly associated with the total number of neurological symptoms and with the prevalence of specific symptoms of the nervous system and mucous membrane irritation. The adjusted odds ratio of neurovegetative lability (1.7-5.9), abnormal or reduced smell (1.6-4.1), memory loss (1.8), and mucous membrane irritation symptoms (1.5-4.6) significantly increased in the exposed group, especially when the summation index of exposure exceeded one.

Autonomic dysfunction in peripheral nerve disease

Autonomic neuropathies are inherited or acquired neuropathies in which autonomic nerve fibers are selectively or disproportionately affected. Generally, sympathetic and parasympathetic fibers are both affected but there are exceptions. Acquired cases can be autoimmune; due to diabetes, amyloidosis, drugs, or toxins; or idiopathic. Autoimmune autonomic neuropathy is often subacute, sometimes associated with a neoplasm, and associated with high titers of antibody to ganglionic nicotinic acetylcholine receptor in about half of the severe cases. The molecular basis of inherited autonomic neuropathies is better known, including recent identification of the loci and genes of hereditary sensory and autonomic neuropathies types I, III, and IV. The inherited amyloid neuropathies are due to mutations of three proteins: transthyretin, apolipoprotein A1, and gelsolin. Non-invasive autonomic testing complements clinical and electrophysiological characterization of the autonomic neuropathies.

Controversies in neurotoxicology: current status

Several controversial neurotoxic syndromes have received notoriety in the past several decades. For each, the controversy involves the most fundamental question about the existence of the disorder as a clinically diagnosable entity. Interestingly, the most controversial of these syndromes share several features, including argument about the existence of each syndrome in the courtroom. The authors focus their discussion on three problems (painter's encephalopathy, silicone breast implant neurotoxicity, and the Gulf War syndrome) for which no scientific consensus has been reached that would establish them as diagnosable disorders. These syndromes do not meet traditional disease criteria, and until a clear set of symptoms and objective signs can be defined, a definite course and clear cause demonstrated, and specific tests and treatments identified, these syndromes are likely to remain highly controversial.

Neurologic evaluation of workers previously diagnosed with solvent-induced toxic encephalopathy

We examined 52 railroad workers with long-term occupational solvent exposures (average 22 years duration) who had been previously diagnosed by others as having solvent-induced toxic encephalopathy. All described episodes of transient intoxication associated with occupational solvent exposure. Persistent symptoms developed, an average, 16 years after exposure onset and included impaired memory (38), altered mood (21), imbalance (18), and headache (17). Thirteen workers had mild mental status abnormalities, but none fulfilled conventional clinical criteria for encephalopathy or dementia. None had abnormal blink reflex (51) or abnormal electroencephalographic (39) studies. Eight of 47 magnetic resonance imaging studies showed evidence of scattered ischemic lesions among workers with known diabetes mellitus (2), elevated blood pressure (4), or peripheral vascular disease (2). One magnetic resonance imaging scan showed mild cortical atrophy. In stepwise multiple linear and logistic regression models, no statistically significant (P < 0.05) dose-response relationships were found between exposure duration and symptoms or signs that were suggestive of encephalopathy. However, the number of symptoms (P < 0.001) and the number of signs (P = 0.05) were associated with current use of central nervous system-active medications. Further, lower Mini-Mental Status Examination scores were associated with a history of alcohol abuse (P = 0.01) and lower educational level (P = 0.03). The number of chief symptoms involving memory, mood, balance, or headache differed significantly among workers in different geographic sites (F(3.48) = 2.94, P = 0.04), a finding that was not explained by job title or exposure duration. There also was a significant (P = 0.0001) inverse relationship between initial exposure year (r2 = 0.60) or total years of exposure through 1987 (r2 = 0.56) and interval to major neurologic symptom onset, suggesting that factors other than solvent exposure account in part for worker complaints. We found no objective neurologic evidence supportive of toxic encephalopathy or any other uniform syndrome among these individuals, and most complaints were explained by neuropsychological factors or conditions unrelated to occupational solvent exposure.

The diagnosis and management of solvent-related disorders

Millions of workers in the United States are recurrently exposed to solvents throughout their working lives. Members of this class of compounds share the ability to dissolve waxes, fats, and oils as their common characteristic. This review offers the health practitioner a practical approach to the diagnosis, management, and prevention of solvent-related disorders that result from exposures to these compounds in the workplace. A description of commonly used solvents is provided, along with a brief review of the literature that documents their acute and chronic effects on health.

Absence of polyneuropathy among workers previously diagnosed with solvent-induced toxic encephalopathy

An association between polyneuropathy and occupational exposure to trichloroethylene, trichloroethane, perchloroethylene, or similar solvents alone or in combination is controversial. We sought to determine whether workers previously diagnosed with solvent-induced toxic encephalopathy had objective evidence of polyneuropathy. Thirty railroad workers previously diagnosed with toxic encephalopathy were examined in the context of litigation against their employers. All described long-term occupational solvent exposure averaging 20 years in duration (range, 10 to 29 years) and producing acute intoxication on a regular basis. The diagnosis of subclinical or clinical polyneuropathy was established using a combination of symptoms, signs, and nerve conduction study (NCS) measures, consistent with standard clinical practice. Potential confounders were identified. NCS results were compared with historical controls, including unexposed workers matched by gender, age, and body mass index. Dose-response relationships were evaluated using simple linear and stepwise regression models. Three workers fulfilled clinical polyneuropathy criteria. The only worker fulfilling NCS criteria for confirmed clinical polyneuropathy had diabetes mellitus. Mean NCS values for most measures were similar to control values, and existing differences in sensory amplitudes disappeared when compared with the matched control group. NCS measures were not significantly influenced by exposure duration or job title. Separation into groups on the basis of the presence or absence of polyneuropathy symptoms, previous diagnosis of polyneuropathy, disability status, and severity or type of encephalopathy did not demonstrate significant NCS differences. The complaints of these workers claiming neurotoxic injury from occupational solvent exposure are not explained by peripheral nervous system dysfunction.

n-Hexane neuropathy due to rubber cement sniffing

n-Hexane neuropathy has been described after glue sniffing and industrial exposure. Onset may be subacute and reminiscent of Guillain-Barré syndrome. Although the primary pathology is axonal, electrophysiologic evaluation is frequently most remarkable for conduction slowing. We describe a patient with a severe subacute neuropathy following n-hexane exposure via glue sniffing. Although symptoms worsened after termination of exposure ("coasting"), strength gradually improved to near normal. Sources of toxic exposure should be sought in all patients with subacute demyelinating neuropathies.

Congenital insensitivity to pain and anhidrosis with mitochondrial and axonal abnormalities

Hereditary sensory and autonomic neuropathy type IV, or congenital insensitivity to pain with anhidrosis (CIPA), is a rare clinical disorder with only 32 cases reported in the literature. There has been no consistent pathophysiologic defect of the sensory nerve detected by light microscopic examination, but a frequent finding of decreased small myelinated fibers and a uniform finding of decreased unmyelinated fibers by ultrastructural analysis has been reported. Muscle biopsy in a 2-year-old boy with congenital insensitivity to pain with anhidrosis indicated lipid droplet accumulation and reduced cytochrome C oxidase histochemically on light microscopy. Electron microscopic study showed almost absent small unmyelinated nerve axons within the muscle, increased microfilaments, and decreased microtubules in axons, some abnormally enlarged mitochondria, and normal-appearing motor endplates. Biochemical analysis of muscle mitochondrial enzyme function revealed cytochrome c oxidase function to be reduced to 35% of normal, with normal function of the other mitochondrial enzymes.

Peripheral and central conduction in n-hexane polyneuropathy

Electrophysiological findings of 27 males with industrial n-hexane polyneuropathy (HPNP) are presented. The results of needle electromyography and nerve conduction studies were compatible with primarily axonal polyneuropathy with secondary segmental demyelination. Motor conduction velocities were the slowest in distal regions of the nerves. In the proximal nerve segments, which were partly tested by magnetic stimulation of the nerve roots, this slowing was much less pronounced. The reduction in mean motor conduction velocities in the forearm segments of ulnar nerves was more than 30% in comparison to the control group means. This reduction was only 10% in the neck-axilla segments. We think that this finding is a reflection of the distal axonopathy process. Central motor conduction times calculated by transcranial magnetic stimulation and spinal nerve root stimulation were found to be prolonged in HPNP patients, indicating that descending motor pathways are affected in human HPNP.