Influence of solvent exposure and aging on cognitive functioning: an 18 year follow up of formerly exposed floor layers and their controls

The Chemical Exposome of Human Aging

Aging is an inevitable biological phenomenon displayed by single cells and organs to entire organismal systems. Aging as a biological process is characterized as a progressive decline in intrinsic biological function. Understanding the causative mechanisms of aging has always captured the imagination of researchers since time immemorial. Although both biological and chronological aging are well defined and studied in terms of genetic, epigenetic, and lifestyle predispositions, the hallmarks of aging in terms of small molecules (i.e., endogenous metabolites to chemical exposures) are limited to obscure. On top of the endogenous metabolites leading to the onset and progression of healthy aging, human beings are constantly exposed to a natural and anthropogenic "chemical" environment round the clock, from conception till death, affecting one's physiology, health and well-being, and disease predisposition. The research community has started gaining sizeable insights into deciphering the aging factors such as immunosenescence, nutrition, frailty, inflamm-aging, and diseases till date, without much input from their interaction with exogenous chemical exposures. The "exposome" around us, mostly, accelerates the process of aging by affecting the internal biological pathways and signaling mechanisms that result in the deterioration of human health. However, the entirety of exposome on human aging is far from established. This review intends to catalog the known and established associations of the exposome from past studies focusing on aging in humans and other model organisms. Further discussed are the current technologies and informatics tools that enable the study of aging exposotypes, and thus, provide a window of opportunities and challenges to study the "aging exposome" in granular details.

Evaluation of occupational exposure to different levels of mixed organic solvents and cognitive function in the painting unit of an automotive industry

Background: The cognitive function could be affected following exposure to organic solvents.The purpose of this study was to examine the cognitive performance of workers exposed to different levels of organic solvents in a painting unit of an automotive industry. Methods: This case-control study was conducted, in 2017, on 121 and 111 workers from the painting and assembly units of an automotive industry as the case and control groups,respectively. Exposure of workers to organic solvents were determined according to National Institute for Occupational Safety and Health (NIOSH) method. The cognitive performance of the studied population was evaluated by the computerized tests. Results: The obtained scores of the N-Back in 1 and 2 blocks and the simple reaction time tests(SRTTs) were significantly differed in the exposed group (p<0.05). No significant difference was observed between case and control groups in the Stroop test score (p> 0.05). Moreover, a significant relationship between the hazard quotient and the cognitive function test scores were observed except the Stroop test. Conclusion: Exposure to organic solvents affect the cognitive functions even below the Occupational Exposure Limits (OELs). Moreover, workers with high exposure levels of organic solvents had highest risk of poor memory and reaction time.

Chronic solvent-induced encephalopathy: course and prognostic factors of neuropsychological functioning

PURPOSE

Working in conditions with daily exposure to organic solvents for many years can result in a disease known as chronic solvent-induced encephalopathy (CSE). The aims for this study were to describe the neuropsychological course of CSE after first diagnosis and to detect prognostic factors for neuropsychological impairment after diagnosis.

METHODS

This prospective study follows a Dutch cohort of CSE patients who were first diagnosed between 2001 and 2011 and underwent a second neuropsychological assessment 1.5-2 years later. Cognitive subdomains were assessed and an overall cognitive impairment score was calculated. Paired t tests and multivariate linear regression analyses were performed to describe the neuropsychological course and to obtain prognostic factors for the neuropsychological functioning at follow-up.

RESULTS

There was a significant improvement on neuropsychological subdomains at follow-up, with effect sizes between small and medium (Cohen's d 0.27-0.54) and a significant overall improvement of neuropsychological impairment with a medium effect size (Cohen's d 0.56). Prognostic variables for more neuropsychological impairment at follow-up were a higher level of neuropsychological impairment at diagnosis and having a comorbid diagnosis of a psychiatric disorder at diagnosis.

CONCLUSIONS

Results are in line with previous research on the course of CSE, stating that CSE is a non-progressive disease after cessation of exposure. However, during follow-up the percentage patients with permanent work disability pension increased from 14 to 37%. Preventive action is needed in countries where exposure to organic solvents is still high to prevent new cases of CSE.

Evolutionary perspective on sex differences in the expression of neurological diseases

Sex-specific brain and cognitive deficits emerge with malnutrition, some infectious and neurodegenerative diseases, and often with prenatal or postnatal toxin exposure. These deficits are described in disparate literatures and are generally not linked to one another. Sexual selection may provide a unifying framework that integrates our understanding of these deficits and provides direction for future studies of sex-specific vulnerabilities. Sexually selected traits are those that have evolved to facilitate competition for reproductive resources or that influence mate choices, and are often larger and more complex than other traits. Critically, malnutrition, disease, chronic social stress, and exposure to man-made toxins compromise the development and expression of sexually selected traits more strongly than that of other traits. The fundamental mechanism underlying vulnerability might be the efficiency of mitochondrial energy capture and control of oxidative stress that in turn links these traits to current advances in neuroenergetics, stress endocrinology, and toxicology. The key idea is that the elaboration of these cognitive abilities, with more underlying gray matter or more extensive inter-modular white matter connections, makes them particularly sensitive to disruptions in mitochondrial functioning and oxidative stress. A framework of human sexually selected cognitive abilities and underlying brain systems is proposed and used to organize what is currently known about sex-specific vulnerabilities.

Evolution of Sex Differences in Trait- and Age-Specific Vulnerabilities

Traits that facilitate competition for reproductive resources or that influence mate choice generally have a heightened sensitivity to stressors. They have evolved to signal resilience to infectious disease and nutritional and social stressors, and they are compromised by exposure to man-made toxins. Although these traits can differ from one species or sex to the next, an understanding of the dynamics of competition and choice can in theory be used to generate a priori predictions about sex-, age-, and trait-specific vulnerabilities for any sexually reproducing species. I provide a review of these dynamics and illustrate associated vulnerabilities in nonhuman species. The age- and sex-specific vulnerability of such traits is then illustrated for stressor-related disruptions of boys’ and girls’ physical growth and play behavior, as well as for aspects of boys’ and girls’ and men’s and women’s personality, language, and spatial abilities. There is much that remains to be determined, but enough is now known to reframe trait sensitivity in ways that will allow scientists and practitioners to better identify and understand vulnerable human traits, and eventually ameliorate or prevent their expression.

Can Neglected Tropical Diseases Compromise Human Wellbeing in Sex-, Age-, and Trait-Specific Ways?

Traits that facilitate competition for reproductive resources or that influence mate choice have evolved to signal resilience to infectious disease and other stressors. As a result, the dynamics of competition and choice can, in theory, be used to generate predictions about sex-, age-, and trait-specific vulnerabilities for any sexually reproducing species, including humans. These dynamics and associated vulnerabilities are reviewed for nonhuman species, focusing on traits that are compromised by exposure to parasites. Using the same approach, sex-, age-, and trait-specific vulnerabilities to parasitic disease are illustrated for children's and adolescent's physical growth and fitness. Suggestions are then provided for widening the assessment of human vulnerabilities to include age-appropriate measures of behavioral (e.g., children's play) and cognitive (e.g., language fluency) traits. These are traits that are likely to be compromised by infection in age- and sex-specific ways. Inclusion of these types of measures in studies of neglected tropic diseases has the potential to provide a more nuanced understanding of how these diseases undermine human wellbeing and may provide a useful means to study the efficacy of associated treatments.

Background Noise Contributes to Organic Solvent Induced Brain Dysfunction

Occupational exposure to complex blends of organic solvents is believed to alter brain functions among workers. However, work environments that contain organic solvents are also polluted with background noise which raises the issue of whether or not the noise contributed to brain alterations. The purpose of the current study was to determine whether or not repeated exposure to low intensity noise with and without exposure to a complex blend of organic solvents would alter brain activity. Female Fischer344 rats served as subjects in these experiments. Asynchronous volume conductance between the midbrain and cortex was evaluated with a slow vertex recording technique. Subtoxic solvent exposure, by itself, had no statistically significant effects. However, background noise significantly suppressed brain activity and this suppression was exacerbated with solvent exposure. Furthermore, combined exposure produced significantly slow neurotransmission. These abnormal neurophysiologic findings occurred in the absence of hearing loss and detectable damage to sensory cells. The observations from the current experiment raise concern for all occupations where workers are repeatedly exposed to background noise or noise combined with organic solvents. Noise levels and solvent concentrations that are currently considered safe may not actually be safe and existing safety regulations have failed to recognize the neurotoxic potential of combined exposures.

Neurobehavioral effects of occupational exposure to organic solvents among male printing workers in Hong Kong

The objective of this study was to investigate the neurobehavioral effects of long-term occupational exposure to low levels of organic solvent among male printing workers in Hong Kong. A total of 115 printing workers exposed to organic solvents were recruited from the printing divisions of 3 printing factories, and 101 workers from the binding divisions of the same factories constituted the comparison group. Active and passive samplings were used to assess the occupational exposures to solvents. The World Health Organization Neurobehavioral Core Test Battery (WHO-NCTB) was applied to assess the neurobehavioral functions. Both active and passive sampling results showed that solvent levels were higher in the printing divisions than the binding divisions. The scores of Digit Symbol and Pursuit Aiming were poorer among workers in the printing divisions (all p values < .05). There were no significant differences found between the 2 divisions for other WHO-NCTB tests. The scores of Digit Symbol and Pursuit Aiming showed exposure-response relationship with various solvent exposure indices. Prolonged occupational exposure to low levels of organic solvents was associated with adverse neurobehavioral effects among male printing workers in Hong Kong.

Neurotoxicity of solvents

Worldwide, several hundred million tons of organic solvents are used annually in household, industry, and other occupational settings. Millions of workers are regularly exposed to organic solvents considered neurotoxic. Acute neurotoxicity due to high exposure of solvent is usually evident, but the nature of long-term effects, such as chronic solvent encephalopathy (CSE), has raised uncertainty even among experts. Earlier studies were criticized for their methodology, mainly epidemiologic studies or investigations of exposed groups with many possible confounders and inadequate exposure assessment. However, an increasing number of studies have been performed since, also on workers with defined CSE based on differential diagnostics. During the last decade, evidence has emerged to enable identification of CSE, a necessity for the early recognition and prevention of progression of dysfunction and disability. Selected chemicals are presented here due to their widespread use, neurotoxic potential, and ability to cause solvent encephalopathy. Constant introduction of new chemicals may introduce new hazardous chemicals or known chemicals may reveal new health effects. It is important to keep an open mind for new findings of solvent-related neurobehavioral effects.

Time may not fully attenuate solvent-associated cognitive deficits in highly exposed workers

OBJECTIVE

To test the effects of lifetime occupational solvent exposure, as measured by dose and timing, on performance on multiple cognitive tests among retired French utility workers.

METHODS

A total of 2,143 retirees in the GAZEL cohort underwent cognitive testing in 2010. Lifetime exposure to chlorinated solvents, petroleum solvents, and benzene was assessed using a job exposure matrix. We modeled effects of lifetime solvent dose, timing of last exposure, and a combination of these metrics on risk for cognitive impairment.

RESULTS

Thirty-three percent of participants were exposed to chlorinated solvents, 26% to benzene, and 25% to petroleum solvents. High exposure to solvents was significantly associated with poor cognition; for example, those highly exposed to chlorinated solvents were at risk of impairment on the Mini-Mental State Examination (risk ratio 1.18; 95% confidence interval 1.06, 1.31), the Digit Symbol Substitution Test (1.54; 1.31, 1.82), semantic fluency test (1.33; 1.14, 1.55), and the Trail Making Test B (1.49; 1.25, 1.77). Retirees at greatest risk for deficits had both high lifetime exposure to solvents and were last exposed 12 to 30 years before testing. Risk was somewhat elevated among those with high lifetime exposure who were last exposed 31 to 50 years before testing. Those with high, recent exposure exhibited impairment in almost all domains, including those not typically associated with solvent exposure.

CONCLUSIONS

While risk of cognitive impairment among moderately exposed workers may attenuate with time, this may not be fully true for those with higher exposure. This has implications for physicians working with formerly solvent-exposed patients as well as for workplace exposure limit policies.

Assessment of neuro behavioral disorders in workers exposed to organic solvents in a publication house

BACKGROUND

Organic solvents are known as a group of organic compounds, widely used in industry and to which many workers are exposed. Neurotoxicity is one of the most important complications of the chronic exposure to the solvents and may causes neurobehavioral disorders in workers. We have studied the frequency of neurobehavioral disorders in workers exposed to organic solvents in one of the publishing houses in Tehran.

METHODS

In this cross-sectional study, 510 workers of a publishing house, having been employed at least a year before the research, were selected to be studied. Among them, 345 workers had been exposed to organic solvents and the other (165 workers) had not. Data were collected using a questionnaire. This questionnaire included demographic and occupational information, and the Swedish Q16 questionnaire. Variables included age, duration of employment, working shift, and smoking. Then we compared both groups in terms of neurobehavioral disorders, using statistical methods.

RESULTS

The mean score of the Swedish Q16 questionnaire in the exposed group (4.8±4.4) was significantly higher than the non-exposed group (3.2±3.1) (p=0.001). According to the questionnaire score, the frequency of neurobehavioral disorders in the exposed group was 38% and in the non-exposed group was 22% (p=0.001). We estimated that the frequency of neurobehavioral disorders in the exposed group was significantly higher than the non-exposed group (p<0.05) using regression analysis and removal of the confounding factors.

CONCLUSION

This study shows that the frequency of the neurobehavioral disorders in the exposed group is significantly higher than the non-exposed group.

Chronic solvent-induced encephalopathy: European consensus of neuropsychological characteristics, assessment, and guidelines for diagnostics

INTRODUCTION

The presence of neuropsychological impairment is a hallmark of chronic solvent-induced encephalopathy (CSE), and using clinical neuropsychological procedures to generate a valid assessment of the condition is crucial for its diagnosis. The goals of this consensus document are to provide updated knowledge of the neuropsychological characteristics of CSE and to provide internationally acceptable guidelines for using neuropsychological assessments in the process of diagnosing patients who are suspected of having CSE.

MATERIALS AND METHODS

A European working group that was composed of experts in the field of the clinical diagnosis of CSE met at several round-table meetings and prepared this report. The first section of the consensus paper addresses a review of the relevant literature that was published between 1985 and March 2012. The second section addresses recommendations for the clinical neuropsychological assessment of patients who are suspected of having CSE.

RESULTS

The literature review indicates that the most common neuropsychological impairments in CSE patients are within the domains of attention, particularly the speed of information processing, memory, and motor performance. It appears that the influence of CSE on memory processes mainly involves immediate recall and generally involves verbal, visual and visuospatial material. In the second section, six recommendations are presented regarding important functional domains for the neuropsychological diagnostic process of CSE that relate to the evaluation of neuropsychological impairment, the assessment and evaluation of symptoms, differential diagnostic considerations, the reliability and validity of neuropsychological test results, and the retesting of patients.

DISCUSSION AND CONCLUSIONS

These recommendations will contribute to the improvement of the process for accurately diagnosing CSE, better counselling for CSE patients, the comparability of epidemiological data between countries, and finally, by raising awareness, these recommendations will contribute to combating the adverse health effects of occupational exposure to solvents.

Somatic symptoms among cosmetologists compared to women in other occupations

BACKGROUND

Although the literature pertaining to the cosmetology occupation and specific health effects, such as asthma, dermatitis, and reproductive function, has grown substantially, little information is available about whether cosmetologists are at increased risk of other symptoms compared to women working in other occupations. Thus, the purpose of this study was to determine if cosmetologists of reproductive age are at increased risk of self-reported symptoms compared to women of the same age working in other occupations.

METHODS

Data were analyzed from 450 cosmetologists and 511 women in other occupations, aged 21-55 years, in the Baltimore metropolitan region who responded to a mailed survey that ascertained detailed data on symptoms as well as usual work tasks.

RESULTS

The data showed that cosmetologists were at increased risk of memory and sleep disturbances, muscle weakness, throat irritation, and hot flashes compared to women of the same age working in other occupations after adjustment for confounders, including cigarette smoking. Among the cosmetologists, handling cleaning supplies; hair bleaching; use of straighteners, texturizers, or permanent chemicals; and several nail care work tasks were associated with one or more of the queried symptoms.

CONCLUSIONS

Findings from this study suggest that, compared to noncosmetologists, cosmetologists are at increased risk for a number of symptoms reported to be associated with decreased quality of life. These symptoms may also reflect chronic exposure to chemicals that have been shown to be related to more severe long-term health outcomes.

Occupational exposure to solvents and cognitive performance in the GAZEL cohort: preliminary results

BACKGROUND

The impact of occupational exposure to solvents on cognitive ageing remains unclear. We examined whether long-term occupational exposure is associated with poor cognitive performance in late midlife.

METHODS

Participants in the GAZEL cohort, set up in 1989, are employees of the French national electricity and gas company. Data on the working environment were used to create measures of cumulative exposures to solvents using a job-exposure matrix. In 2002-2004, cognitive performance was assessed using the Digit Symbol Substitution Test (DSST) and the Mini Mental State Examination in 5,242 participants (aged 55-65 years).

RESULTS

In cross-sectional analysis using multiple logistic regression, there was a greater risk of poor cognitive performance (DSST score <25th percentile) among those with high exposure to benzene (OR = 1.58; 95% CI 1.31-1.90) and the grouped categories of chlorinated (OR = 1.39; 95% CI 1.3-2.3), aromatic (OR = 1.76; 95% CI 1.08-2.87), and petroleum solvents (OR = 1.50; 95% CI 1.23-1.81).

CONCLUSIONS

These results suggest that occupational exposures to solvents may be associated later in life with cognitive impairment, even after taking into account the effects of education, employment grade, and numerous health factors.

Can intensive use of alcohol-based hand rubs lead to passive alcoholization?

Hand disinfection with alcohols-based hand rubs (ABHRs) are known to be the most effective measure to prevent nosocomial infections in healthcare. ABHRs contain on average 70% by weight of one or more alcohols. During the hand rubbing procedure, users are exposed to these alcohols not only through dermal contact, but also via inhalation, due to the physical and chemical properties of alcohols volatilizing from alcoholic solutions or gels into the air. Ethanol ingestion is well known to increase risks of several diseases (affecting the pancreas, liver, cardiovascular system…), but there is a lack of knowledge about the effects of exposure to other alcohols (including n- or isopropanol) via inhalation and dermal contact, despite the worldwide use of ABHRs. This work aims at discussing possible health effects related to unintentional alcoholization (via inhalation and dermal contact) from professional ABHR usage to suggest the need for more research in this area (but not to question the value of ABHRs). Based upon an average of 30 hand rubbings per healthcare professional per day, it can be assumed that a healthcare worker may be exposed to a maximum 5,500 mg/m(3) per work shift, five times above the recommended occupational time weighted average limit. Thus, in order to answer the question posed in the title, studies on spatial and temporal variability of alcohol emission from ABHRs in real world situations and studies on certain high risk individuals are needed.

Neurobehavioral impairment in children occupationally exposed to mixed organic solvents

BACKGROUND

Our previous work has demonstrated adverse effects on neuropsychological and neurobehavioral function in solvent-exposed working children compared to non-exposed working and school children. The aim of this paper was to examine the dose-response relationships between neurobehavioral function and solvent exposure in children.

METHODS

We tested 120 male children aged 10-17 years (100 working solvent-exposed, 10 working children, 10 school children). Neurotoxic effects were assessed through a questionnaire and a selection of neurobehavioral tests. Workplace exposure to a mixture of solvents was measured using personal passive samplers.

RESULTS

Children with higher solvent exposure showed significantly higher reporting of neurotoxic symptoms (P=0.02). Importantly, multiple regression models revealed significant dose-response relationships, with higher cumulative exposure associated with poorer performance on the Choice Reaction Time, Symbol Digit, Continuous Performance, Digit Span and Grooved Pegboard tests.

CONCLUSIONS

This study provides the first empirical evidence of a dose-response association between exposure to solvents and neurobehavioral performance in working children. This finding implies that solvent-exposed working children are at high risk of developing neurobehavioral impairments. These impairments are likely to interfere with their capacity to respond quickly and safely to new demands and to learn new information.

Psychological effects of occupational exposure to organic solvent mixtures on printers

PURPOSE

Neuropsychiatric symptoms associated with long-term exposure to organic solvents have been investigated for a long time in many occupational studies. The aim of our study was to identify preclinical effects of low-level chronic solvent exposure on the cognitive performance of silk-screen printers.

METHODS

A cross-sectional study was conducted including 38 printers which were exposed to organic solvent mixtures and 45 controls without neurotoxic exposure. The psychometric test battery included nine tests and two questionnaires.

RESULTS

The sum of scales or the total score of the PNF was also significantly (p <0.001) higher in the exposed group than in the non-exposed. The printers performed worse in some psychometric tests than did controls. Cross validation with the psychometric performances resulted in 69.6% of participants being correctly classified (55.9% printers and 80% controls). Highly significant differences (p<0.001) between both groups of exposed and non-exposed workers were found for the mean values of the multidimensional psychometric score.

CONCLUSIONS

These results of our study proved not only that chronic exposure to organic solvent mixtures could induce a psychological effect but also that the psychological/psychometrical tests performed in this study were capable of predicting neurotoxicity.

The course of chronic solvent induced encephalopathy: a systematic review

BACKGROUND

Worldwide millions of workers are exposed to organic solvents. Long term exposure leads in some workers to the development of Chronic Solvent induced Encephalopathy (CSE). The first reports about CSE came from the European Nordic countries in the 1970s. In spite of decades of experience with this disease, little is known about the course and prognostic factors of CSE.

OBJECTIVE

To provide an overview of the evidence about the course and prognostic factors of CSE.

METHODS

A systematic review was conducted. Databases PubMed, PsycINFO (1970-2008) and EMBASE (1980-2008) were searched with the search strategy: solvent AND follow up AND (encephalopathy OR chronic intoxication). Inclusion criteria were: written in English, study population of CSE patients, follow-up time of at least 1 year. Included articles were assessed on methodological quality.

RESULTS

Sixty unique articles were retrieved of which sixteen met the inclusion criteria. Data extraction provided information about domains of neurology, neuropsychology, physical and mental health perceptions, and social consequences. In a number of studies no significant changes, and in other studies improvement of functioning could be measured. Prognostic factors resulting from included studies were summarized for each domain indicating a potential positive influence of younger age and lower exposure variables.

DISCUSSION

Due to the large heterogeneity of methodology no levels of evidence could be obtained. This review shows that there is a need for future research that addresses a variety of domains of functioning, hopefully resulting in an overall prognostic model for CSE.

CONCLUSION

Studies in this review are in agreement about CSE being a non-progressive disease in which no severe deterioration of functioning occurs after diagnosis. In a number of studies no significant changes, and in other studies improvement of functioning could be measured. Presumably cessation of exposure might be one of the causal factors for the non-progressive character of the disease as has been found. Future studies are needed to clarify the role of various prognostic factors on the course of CSE.

Épidémiologie des démences

Dementia is a major public health problem and its burden will increase in the 30 years to come. Prevalence increases with age and incidence is slightly higher in women than men, especially after the age of 80 years. Survival after the onset of dementia is approximately 5 years. Lifestyle and health habits are a keystone for dementia: risk factors include physical, intellectual and social activity and nutritional habits. Data from well-conducted intervention studies are necessary to show whether better care for hypertension, diabetes, and dyslipidemia might decrease the incidence of dementia.

Self-reported symptoms and their effects on cognitive functioning in workers with past exposure to solvent-based glues: an 18-year follow-up

OBJECTIVES

To examine to what extent exposure to organic solvents during the working life affects general well-being in the long term, and to explore the relationship between self-reported symptoms and cognitive functioning in previously solvent-exposed floor layers.

METHODS

The study included 41 solvent-exposed floor layers and 40 unexposed referents participating in a longitudinal follow-up study 18 years after the baseline assessment. Symptom prevalence and level of spare time activities were studied using the same methods as in the initial study. These include a general health examination, the Q16 symptom questionnaire, and a questionnaire for spare time activities. Relationships between symptoms and cognitive functioning were analysed based on recently published data on cognitive functioning of the participants at follow-up.

RESULTS

At follow-up neuropsychiatric symptoms such as need to check things, depressive mood, and abnormal fatigue, were more prevalent among floor layers, particularly the most exposed individuals, than among referents. In addition, the most highly exposed floor layers reported more concentration difficulties and irritability. Fatigue and depressive mood increased over the follow-up time in the most exposed floor layers but not in the referents. Memory difficulties, although more frequent among floor layers than among referents, had decreased in floor layers while increased in referents. Floor layers also reported some negative effects on intimate relations and activity level. Neuropsychiatric symptoms were related to poorer performance chiefly in memory tasks and tests of complex attention and perceptual speed, more seldom in visuospatial tasks.

CONCLUSIONS

Findings of exposure-related, long-lasting, partly deteriorating neuropsychiatric complaints indicate that general well-being later in life has been affected in floor layers with past heavy solvent exposure. We also found frequent associations between symptom prevalence and the cognitive functioning. Together with previous findings of dose-related cognitive decrements, the present results strengthen the evidence that long-term heavy occupational solvent exposure may negatively interact with the normal ageing process.

Strategies for dissecting genetic-environmental interactions in neurodegenerative disorders

Complex genetic and environmental interactions contribute to abnormal aging and neurodegenerative disorders. We present information from a series of 1136 consecutive patients presenting with cognitive disorders and show possible significant contribution of toxic environmental and occupational exposures to pathological aging (21% of patients) and interactions of these exposures with common polymorphisms that affect cell injury and inflammation. Such exposures may lower age of onset to same degree as APOE4/4. Common polymorphisms in apolipoprotein E (APOE), hemochromatosis gene (Hfe) and alpha-1-antitrypsin (AAT) are present in up to 40+% of patients and may partially account for differences in clinical syndrome, age of onset and rate of progression. Strategies for the study of these disorders must also consider the role and treatment of common co-morbid illnesses such as alcohol use, nutritional deficiencies, sleep disorders, and pre-existing affective disorder. APOE, Hfe, and AAT genes are expressed in liver tissue and in macrophages and are involved in the host innate immune response to stress, inflammation and infections. Hfe and AAT are involved in iron metabolism and their polymorphisms may contribute to hepatosteatosis and altered homeostasis of lipids (role of APOE), iron, and trace minerals. Some of these responses may be adaptive. Hfe and AAT modulate the apparent effects of toxic exposures on age of onset and progression rate. C282Y polymorphism paradoxically reverses APOE4/4 effect on age of onset. S and Z AAT polymorphisms may attenuate earlier age of onset in persons with toxic or environmental exposure. AAT S or Z polymorphisms are present in 25% of persons with anxiety disorder and 42% of persons with bipolar disorder compared to 10% of control group without pre-existing affective disorder. Common genetic polymorphisms that affect the response to inflammation and cell injury provide a beginning strategy for dissecting neurodegenerative disorders. The effects of APOE, Hfe, and AAT on glucose, lipid, iron and trace mineral homeostasis may affect normal development and aging of the nervous system in addition to their effects on outcome of toxic environmental and occupational exposures and susceptibility and outcome of neurodegenerative illnesses.

Neuropsychiatric symptoms and past manganese exposure in a ferro-alloy plant

INTRODUCTION

Psychiatric manifestations have been reported in cases of manganism, and mood disorders are often observed in manganese (Mn) exposed workers. We examined neuropsychiatric symptoms among formerly Mn-exposed workers 14 years after cessation of exposure.

MATERIALS AND METHODS

A study was conducted in 1990 among workers from a ferro- and silico-Mn plant and unexposed working men referents from the same region in South-West Quebec. At follow-up in 2004, 77 former Mn-workers and 81 referents agreed to participate and responded to a neuropsychiatric symptom checklist, the Brief Symptom Inventory (BSI); scores were transformed into T-scores based on a normative population. Cumulated exposure indices (CEI) were computed for each former Mn-worker. Linear and logistic regression analyses were used.

RESULTS

Mean T-scores were significantly higher among former Mn-workers than referents on scales of Depression and Anxiety. Mean T-scores of psychological distress increased with the CEI tertiles, with significant associations for the scales Somatization, Depression, Anxiety and Hostility. Former Mn-workers in the two highest tertiles of CEI showed a higher risk for T-scores >or=63 for Hostility (OR, 7.5; 95% CI, 1.5-38.9), Depression (OR, 2.6; 95% CI, 1.1-8.4) and Anxiety (OR, 3.0; 95% CI, 1.1-8.4).

CONCLUSION

These results suggest that past exposure to Mn may have lasting consequences on neuropsychiatric symptoms.

Longitudinal study to explore chronic neuropsychologic effects on solvent exposed workers

AIM

The aim of the study was to examine possible neurotoxic effects on the central nervous system (CNS) in relation to a chronic solvent exposure at the workplace.

METHOD

The collective included 127 workers exposed to solvent mixtures, such as spray painters and printers. They were examined twice by means of a physical examination, neuropsychological testbattery, biological and air monitoring.

RESULTS

Major component of the solvents were white spirits in concentrations up to 127 ppm in air and 2,666 microg/l in blood. Single substances were mainly toluene and xylenes in concentrations below current threshold values at the workplace. During the 2 yr interval, the concentrations of solvents decreased, and no significant associations between the neuropsychological tests and the solvent exposure were found. Regarding the whole working history of each participant, we found a significant reduction on information processing velocity and performance in the trailmaking test, as well as more complaints of workers with higher solvent exposure in the past.

CONCLUSIONS

A slight increase of subjective complaints and a deteriorated power of concentration seems to be associated with chronic solvent exposure.

Manganese exposure and age: neurobehavioral performance among alloy production workers

Manganese (Mn) is associated with neurotoxic effects under certain conditions of exposure. A recent study on environmental Mn exposure showed an Mn×age interaction for several neurobehavioral functions. The objective of the present study was to examine the neurobehavioral test results in relation to age and Mn exposure, using an existing data set on 74 workers from an Mn alloy production plant and referents pair-matched for age (±3 years), educational level (±2 years), number of children, and smoking status. The pair differences between Mn-exposed workers and referents increased significantly with age for scores on Delayed Word Recall, Trail Making B, Cancellation H, Nine-Hole Hand Steadiness Test, and Vibratometer. These results suggest that for certain neurobehavioral functions, and in particular for information processing, Mn-related deficits increase with age. This outcome could not be explained by higher cumulative Mn exposure.

The Relation of Occupational Organic Solvent Exposure to Symptom Reporting in a Sample of White and Chinese Midlife Women

OBJECTIVE

This study examined the relation of occupational solvent exposure to menopausal and other symptoms in midlife women.

METHODS

We conducted a cross-sectional study of 480 Chinese and 494 white women, aged 40-55 years, in Northern California. Levels of exposure to organic solvents (none, low, medium, or high) were assigned to each current job using a job-exposure matrix.

RESULTS

A lower proportion of women with low occupational organic solvent exposure reported hot flashes or night sweats than working women with no solvent exposure (adjusted prevalence odds ratio [APOR] = 0.48, 95% confidence interval [CI] = 0.19-1.21). A greater proportion of women with high solvent exposure reported forgetfulness than women with no exposure (APOR = 2.51, 95% CI = 1.12-5.63).

CONCLUSIONS

Some symptom reporting in midlife women was related to their occupational organic solvent exposure.

Solvent-related health effects among construction painters with decreasing exposure

BACKGROUND

The prevalence of solvent-related symptoms among construction painters is unclear due to their declining exposure.

METHODS

A questionnaire study was conducted on 1000 male Finnish construction painters and 1000 carpenters. Symptom questions were combined with exposure parameters, medical history, and health behavior.

RESULTS

Highly significant associations were found between cumulative intensity of long-term solvent exposure (CE-LT) and symptoms of memory and concentration, and mood. CE-LT was a better measure of solvent exposure than the number of years as a painter. Exposure was also associated with diagnosed psychiatric disorders, hypertension and arrhythmia. Recent exposure in the 1990s had no major effect on symptoms.

CONCLUSIONS

The results strengthen the dose-response relationship of exposure and long-term neurotoxic effects. No clear association was found between recent exposure and symptoms. Cardiovascular effects in solvent-exposed construction painters is further suggested.

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.

A search for residual behavioral effects of trichloroethylene (TCE) in rats exposed as young adults

Trichloroethylene (TCE) is an organic solvent with robust acute effects on the nervous system, but poorly documented long-term effects. This study employed a signal detection task (SDT) to assess the persistence of effects of repeated daily inhalation of TCE on sustained attention in rats. Adult male Long-Evans rats inhaled TCE at 0, 1600, or 2400 ppm, 6 h/day for 20 days (n=8/group) and began learning the SDT 3 weeks later. Rats earned food by pressing one retractable response lever in a signal trial and a second lever in a blank (no signal) trial. TCE did not affect acquisition of the response rule or performance of the SDT after the intertrial interval (ITI) was changed from a constant value to a variable one. Increasing the trial presentation rate reduced accuracy equivalently in all groups. Injections of ethanol (0, 0.5, 1.0, 1.5 g/kg ip) and d-amphetamine (0, 0.1, 0.3, 1.0 mg/kg sc) systematically impaired performance as functions of drug dose. d-Amphetamine (1.0 mg/kg) reduced P(hit) more in the 2400-ppm TCE group than in the other groups. All rats required remedial training to learn a reversal of the response contingencies, which TCE did not interfere with. Thus, a history of exposure to TCE did not significantly alter learning or sustained attention in the absence of drugs. Although ethanol did not differentially affect the TCE groups, the effect of d-amphetamine is consistent with solvent-induced changes in dopaminergic functions in the CNS. Calculations indicated power values of 0.5 to 0.8 to detect main effects of TCE for the three primary endpoints.

Dose-Related Cognitive Deficits among Floor Layers with Previous Heavy Exposure to Solvents

The authors used tests of attention and memory, which are sensitive to the influence of aging, to explore possible adverse effects on cognitive functioning following past heavy exposure to solvent-based glues, with special reference to dose-effect relationships and interactions with the aging process. The study included 41 floor layers and 40 carpenters (referents) who participated in a longitudinal follow-up assessment. The authors assessed cognitive functioning with the following tests: trail-making, color words, and word recall. Higher cumulative exposure was associated with poorer test performance that was related to concept shifting, episodic memory, and speed of congruent and incongruent color naming. The magnitude of the decrements in memory tasks was equivalent to about 20 yr of age-related decline. Dose-effect relationships were seen mainly for contact adhesives, and there was partial evidence for an interaction between exposure and aging.