Cognitive effects of chronic exposure to lead and solvents

Chronic Exposure to Solvents Among Construction Painters: Reductions in Exposure and Neurobehavioral Health Effects

OBJECTIVE

The aim of this study was to assess the neurobehavioral effects of lifetime solvent exposure by comparing the performance of painters and demographically comparable controls.

METHODS

Performance of exposed painters (N = 133) was compared with unexposed tapers, glaziers, or carpenters (N = 78) on the following domains: motor/perceptual speed, visual contrast, attention, working memory/planning, and visual and verbal memory. Lifetime exposure was estimated with questionnaires, field measurements, and paint composition.

RESULTS

After controlling for confounders, lifetime solvent exposure did not predict reduction in performance for overall domains of function. Lifetime solvent exposures predicted subtle alterations for individual tests of verbal learning, motor coordination, and visuospatial accuracy.

CONCLUSION

Concentrations of solvents in paints have steadily declined during the working lifetime of subjects in this study. Although reduced performance was observed on individual tests, these alterations were not consistent across tests and unlikely to be of clinical significance.

Lead-induced impairments in the neural processes related to working memory function

Background

It is well known that lead exposure induces neurotoxic effects, which can result in a variety of neurocognitive dysfunction. Especially, occupational lead exposures in adults are associated with decreases in cognitive performance including working memory. Despite recent advances in human neuroimaging techniques, the neural correlates of lead-exposed cognitive impairment remain unclear. Therefore, this study was aimed to compare the neural activations in relation to working memory function between the lead-exposed subjects and healthy controls.

Methodology/Principal Findings

Thirty-one lead-exposed subjects and 34 healthy subjects performed an n-back memory task during MRI scan. We performed fMRI using the 1-back and 2-back memory tasks differing in cognitive demand. Functional MRI data were analyzed using within- and between-group analysis. We found that the lead-exposed subjects showed poorer working memory performance during high memory loading task than the healthy subjects. In addition, between-group analyses revealed that the lead-exposed subjects showed reduced activation in the dorsolateral prefrontal cortex, ventrolateral prefrontal cortex, pre supplementary motor areas, and inferior parietal cortex.

Conclusions/Significance

Our findings suggest that functional abnormalities in the frontoparietal working memory network might contribute to impairments in maintenance and manipulation of working memory in the lead-exposed subjects.

Structural Magnetic Resonance Imaging in an adult cohort following prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water

This population-based retrospective cohort study examined Structural Magnetic Resonance Imaging (MRI) of the brain in relation to prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water on Cape Cod, Massachusetts. Subjects were identified through birth records from 1969 through 1983. Exposure was modeled using pipe network information from town water departments, a PCE leaching and transport algorithm, EPANet water flow modeling software, and Geographic Information System (GIS) methodology. Brain imaging was performed on 26 exposed and 16 unexposed subjects. Scans were acquired on a Philips 3T whole body scanner using the ADNI T1-weighted MP-RAGE scan. The scans were processed by FreeSurfer version 4.3.1 software to obtain measurements of specific brain regions. There were no statistically significant differences between exposed and unexposed subjects on the measures of white matter hypointensities (β: 127.5mm(3), 95% CI: -259.1, 1514.0), white matter volumes (e.g. total cerebral white matter: β: 21230.0mm(3), 95% CI: -4512.6, 46971.7) or gray matter volumes (e.g. total cerebral gray matter: β: 11976.0mm(3), 95% CI: -13657.2, 37609.3). The results of this study suggest that exposure to PCE during gestation and early childhood, at the levels observed in this population, is not associated with alterations in the brain structures studied.

Occupational solvent exposure and cognition: does the association vary by level of education?

OBJECTIVE

Chronic occupational solvent exposure is associated with long-term cognitive deficits. Cognitive reserve may protect solvent-exposed workers from cognitive impairment. We tested whether the association between chronic solvent exposure and cognition varied by educational attainment, a proxy for cognitive reserve.

METHODS

Data were drawn from a prospective cohort of French national gas and electricity (GAZEL) employees (n = 4,134). Lifetime exposure to 4 solvent types (chlorinated solvents, petroleum solvents, benzene, and nonbenzene aromatic solvents) was assessed using a validated job-exposure matrix. Education was dichotomized at less than secondary school or below. Cognitive impairment was defined as scoring below the 25th percentile on the Digit Symbol Substitution Test at mean age 59 (SD 2.8; 88% of participants were retired at testing). Log-binomial regression was used to model risk ratios (RRs) for poor cognition as predicted by solvent exposure, stratified by education and adjusted for sociodemographic and behavioral factors.

RESULTS

Solvent exposure rates were higher among less-educated patients. Within this group, there was a dose-response relationship between lifetime exposure to each solvent type and RR for poor cognition (e.g., for high exposure to benzene, RR = 1.24, 95% confidence interval 1.09-1.41), with significant linear trends (p < 0.05) in 3 out of 4 solvent types. Recency of solvent exposure also predicted worse cognition among less-educated patients. Among those with secondary education or higher, there was no significant or near-significant relationship between any quantification of solvent exposure and cognition.

CONCLUSIONS

Solvent exposure is associated with poor cognition only among less-educated individuals. Higher cognitive reserve in the more-educated group may explain this finding.

Adult neuropsychological performance following prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water

This population-based retrospective cohort study examined adult performance on a battery of neuropsychological tests in relation to prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water on Cape Cod, Massachusetts. Subjects were identified through birth records from 1969 through 1983. Exposure was modeled using pipe network information from town water departments, a PCE leaching and transport algorithm, EPANet water flow modeling software, and a Geographic Information System (GIS). Results of crude and multivariate analyses among 35 exposed and 28 unexposed subjects showed no association between prenatal and early postnatal exposure and decrements on tests that assess abilities in the domains of omnibus intelligence, academic achievement or language. The results were suggestive of an association between prenatal and early postnatal PCE exposure and diminished performance on tests that assessed abilities in the domains of visuospatial functioning, learning and memory, motor, attention and mood. Because the sample size was small, most findings were not statistically significant. Future studies with larger sample sizes should be conducted to further define the neuropsychological consequences of early developmental PCE exposure.

Increased lead biomarker levels are associated with changes in hormonal response to stress in occupationally exposed male participants

BACKGROUND

Lead (Pb) exposure has been associated with a host of pathological conditions in humans. In rodents Pb exposure has been shown to alter the hypothalamic-pituitary-adrenal (HPA) axis function.

OBJECTIVE

We investigated the effects of lead on responses of the HPA axis to a psychosocial laboratory stressor administered to Pb-exposed workers.

METHODS

Seventy male participants completed the Trier Social Stress Test (TSST). Serum cortisol (CORT) and plasma adrenocorticotropic hormone (ACTH) were assessed in response to and during recovery from the stressor. We measured Pb in blood, a biomarker of recent exposure, and in tibia bone by X-ray fluorescence (XRF), a biomarker of chronic exposure.

RESULTS

The TSST induced statistically significant increases in ACTH and CORT in the participants. At baseline, ACTH was not significantly higher (p = 0.052) in participants with higher blood Pb concentration, but CORT was significantly lower in these participants (p = 0.016). Adjusted linear regression models indicated a positive association between blood and bone Pb and the increase in ACTH in response to stress. However, Pb was not strongly associated with changes in CORT in response to stress. Pb was also associated with the ACTH:CORT ratio at baseline and throughout the course of the protocol, suggesting an adrenal hyporesponsiveness in participants with higher Pb concentrations.

CONCLUSION

The altered HPA-axis stress response observed in participants exposed to higher levels of Pb further supports the idea that lead may contribute to a host of biological dysfunctions beyond the classical neurotoxic effects.

Childhood and adult socioeconomic position, cumulative lead levels, and pessimism in later life: the VA Normative Aging Study

Pessimism, a general tendency toward negative expectancies, is a risk factor for depression and also heart disease, stroke, and reduced cancer survival. There is evidence that individuals with higher lead exposure have poorer health. However, low socioeconomic status (SES) is linked with higher lead levels and greater pessimism, and it is unclear whether lead influences psychological functioning independently of other social factors. The authors considered interrelations among childhood and adult SES, lead levels, and psychological functioning in data collected on 412 Boston area men between 1991 and 2002 in a subgroup of the VA Normative Aging Study. Pessimism was measured by using the Life Orientation Test. Cumulative (tibia) lead was measured by x-ray fluorescence. Structural equation modeling was used to quantify the relations as mediated by childhood and adult SES, controlling for age, health behaviors, and health status. An interquartile range increase in lead quartile was associated with a 0.37 increase in pessimism score (P < 0.05). Low childhood and adult SES were related to higher tibia lead levels, and both were also independently associated with higher pessimism. Lead maintained an independent association with pessimism even after childhood and adult SES were considered. Results demonstrate an interrelated role of lead burden and SES over the life course in relation to psychological functioning in older age.

Development of solvent exposure index for construction painters

This article describes methodological approaches for reconstructing long-term occupational exposure to organic solvents among construction painters. A detailed exposure questionnaire was administered to 125 painters to develop a job exposure matrix (JEM). The questionnaire inquired about painting activities with solvent-based paints and use of protection equipment for the previous 25 years in 5-year intervals. Current and historical distributions of solvent air concentrations were assessed for the same time period based on the following information: industrial hygiene measurements, paint composition changes, and VOC emission rate changes from architectural and industrial maintenance coatings. Changes in protection factors of respirators were also assessed. A cumulative solvent exposure index was calculated for each painter through Monte Carlo simulations by combining appropriate input distributions of solvent air concentrations and protection factors of respirators with JEM. Sensitivity simulations revealed that the historical variations in solvent air concentrations had a higher impact on the cumulative solvent exposure index than changes in protection factors for respirators. Fifty-eight percent of painters were classified with a different exposure quartile when the solvent exposure index was used vs. an exposure based only on years using solvent-based paints, suggesting the need for more detailed exposure analysis than just years working when conducting epidemiologic studies for this worker population.

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.

Interaction of stress, lead burden, and age on cognition in older men: the VA Normative Aging Study

BACKGROUND

Low-level exposure to lead and to chronic stress may independently influence cognition. However, the modifying potential of psychosocial stress on the neurotoxicity of lead and their combined relationship to aging-associated decline have not been fully examined.

OBJECTIVES

We examined the cross-sectional interaction between stress and lead exposure on Mini-Mental State Examination (MMSE) scores among 811 participants in the Normative Aging Study, a cohort of older U.S. men.

METHODS

We used two self-reported measures of stress appraisal--a self-report of stress related to their most severe problem and the Perceived Stress Scale (PSS). Indices of lead exposure were blood lead and bone (tibia and patella) lead.

RESULTS

Participants with higher self-reported stress had lower MMSE scores, which were adjusted for age, education, computer experience, English as a first language, smoking, and alcohol intake. In multivariable-adjusted tests for interaction, those with higher PSS scores had a 0.57-point lower (95% confidence interval, -0.90 to 0.24) MMSE score for a 2-fold increase in blood lead than did those with lower PSS scores. In addition, the combination of high PSS scores and high blood lead categories on one or both was associated with a 0.05-0.08 reduction on the MMSE for each year of age compared with those with low PSS score and blood lead level (p < 0.05).

CONCLUSIONS

Psychological stress had an independent inverse association with cognition and also modified the relationship between lead exposure and cognitive performance among older men. Furthermore, high stress and lead together modified the association between age and cognition.

Cumulative exposure to lead in relation to cognitive function in older women

BACKGROUND

Recent data indicate that chronic low-level exposure to lead is associated with accelerated declines in cognition in older age, but this has not been examined in women.

OBJECTIVE

We examined biomarkers of lead exposure in relation to performance on a battery of cognitive tests among older women.

METHODS

Patella and tibia bone lead--measures of cumulative exposure over many years--and blood lead, a measure of recent exposure, were assessed in 587 women 47-74 years of age. We assessed their cognitive function 5 years later using validated telephone interviews.

RESULTS

Mean +/- SD lead levels in tibia, patella, and blood were 10.5 +/- 9.7 microg/g bone, 12.6 +/- 11.6 microg/g bone, and 2.9 +/- 1.9 microg/dL, respectively, consistent with community-level exposures. In multivariable-adjusted analyses of all cognitive tests combined, levels of all three lead biomarkers were associated with worse cognitive performance. The association between bone lead and letter fluency score differed dramatically from the other bone lead-cognitive score associations, and exclusion of this particular score from the combined analyses strengthened the associations between bone lead and cognitive performance. Results were statistically significant only for tibia lead: one SD increase in tibia lead corresponded to a 0.051-unit lower standardized summary cognitive score (95% confidence interval: -0.099 to -0.003; p = 0.04), similar to the difference in cognitive scores we observed between women who were 3 years apart in age.

CONCLUSIONS

These findings suggest that cumulative exposure to lead, even at low levels experienced in community settings, may have adverse consequences for women's cognition in older age.

The impact of solvent mixtures on neurobehavioral performance: conclusions from epidemiological data

The review of epidemiological studies investigating the neurobehavioral effects of occupational exposure to solvent mixtures sought to contribute to the following issues: (1) Identification of affected cognitive and motor functions. (2) Identification of sensitive neuropsychological tests. (3) Analysis of exposure-effect relationships. The approach was based on the meta-analytical method of effect size estimates. Fifty-three groups from occupational studies were included in the meta-analysis. Forty-eight neuropsychological performance variables could be analyzed as they were included in at least three studies. Seventeen articles provided detailed information on the constituents of mixtures, thereby enabling the computation of an exposure index that allowed the comparison of different mixtures. Significant negative effect sizes were obtained for 12 test variables measuring attention, memory, motor performance and constructional abilities. The greatest proportion of lower performance scores in the exposed groups was shown by different tests of attention: significant effect sizes between d=-0.16 and -0.46 were calculated. Tests of cognitive processing speed, response alternation and inhibition seemed to be sensitive tools for the detection of poorer performance. Exposure-effect relationships were mainly characterized by inconsistent patterns. Crude and inappropriately calculated exposure measures were blamed for this outcome. A healthy worker effect was suggested more consistently: studies examining groups with longer exposure duration obtained smaller effect sizes. Indications of confounding were observed; however, they did not seem sufficient to question consistent effect size patterns. Paying greater attention to the measurement of exposure and including measures of confounding is advisable for future studies and would enhance the explanatory power of cross-sectional studies and meta-analyses.

Risk of learning and behavioral disorders following prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water

This population-based retrospective cohort study examined the association between developmental disorders of learning, attention and behavior and prenatal and early postnatal drinking water exposure to tetrachloroethylene (PCE) on Cape Cod, Massachusetts. Subjects were identified through birth records from 1969 through 1983. Exposure was modeled using information from town water departments, a PCE leaching and transport algorithm, EPANet water flow modeling software, and a Geographic Information System (GIS). Mothers completed a questionnaire on disorders of attention, learning and behavior in their children and on potential confounding variables. The final cohort consisted of 2086 children. Results of crude and multivariate analyses showed no association between prenatal exposure and receiving tutoring for reading or math, being placed on an Individual Education Plan, or repeating a school grade (adjusted Odds Ratios (OR)=1.0-1.2). There was also no consistent pattern of increased risk for receiving a diagnosis of Attention Deficit Disorder (ADD) or Hyperactive Disorder (HD), special class placement for academic or behavioral problems, or lower educational attainment. Modest associations were observed for the latter outcomes only in the low exposure group (e.g., adjusted ORs for ADD were 1.4 and 1.0 for low and high exposure, respectively). (All ORs are based on an unexposed referent group.) Results for postnatal exposure through age five years were similar to those for prenatal exposure. We conclude that prenatal and early postnatal PCE exposure is not associated with disorders of attention, learning and behavior identified on the basis of questionnaire responses and at the exposure levels experienced by this population.

Lead burden and psychiatric symptoms and the modifying influence of the delta-aminolevulinic acid dehydratase (ALAD) polymorphism: the VA Normative Aging Study

The authors evaluated the association between lead burden and psychiatric symptoms and its potential modification by a delta-aminolevulinic acid dehydratase (ALAD) polymorphism. Lead measurements in blood or bone and self-reported ratings on the Brief Symptom Inventory from 1991 to 2002 were available for 1,075 US men participating in the Department of Veterans Affairs (VA) Normative Aging Study. The authors estimated the prevalence odds ratio for the association between interquartile-range lead and abnormal symptom score, adjusting for potential confounders. An interquartile increment in tibia lead (14 microg/g) was associated with 21% higher odds of somatization (95% confidence interval of the odds ratio: 1.01, 1.46). An interquartile increment in patella lead (20 microg/g) corresponded to a 23% increase in the odds of global distress (95% confidence interval of the odds ratio: 1.02, 1.47). An interquartile increment in blood lead (2.8 microg/dl) was associated with 14% higher odds of hostility (95% confidence interval of the odds ratio: 1.02, 1.27). In all other analyses, lead was nonsignificantly associated with psychiatric symptoms. The adverse association of lead with abnormal mood scores was generally stronger among ALAD 1-1 carriers than 1-2/2-2 carriers, particularly regarding phobic anxiety symptoms (p(interaction) = 0.004). These results augment evidence of a deleterious association between lead and psychiatric symptoms.

Proton magnetic resonance spectroscopic evidence of glial effects of cumulative lead exposure in the adult human hippocampus

BACKGROUND

Exposure to lead is known to have adverse effects on cognition in several different populations. Little is known about the underlying structural and functional correlates of such exposure in humans.

OBJECTIVES

We assessed the association between cumulative exposure to lead and levels of different brain metabolite ratios in vivo using magnetic resonance spectroscopy (MRS).

METHODS

We performed MRS on 15 men selected from the lowest quintile of patella bone lead within the Department of Veterans Affairs' Normative Aging Study (NAS) and 16 from the highest to assess in the hippocampal levels of the metabolites N-acetylaspartate, myoinositol, and choline, each expressed as a ratio with creatine. Bone lead concentrations-indicators of cumulative lead exposure-were previously measured using K-X-ray fluorescence spectroscopy. MRS was performed on the men from 2002 to 2004.

RESULTS

A 20-microg/g bone and 15-microg/g bone higher patella and tibia bone lead concentration--the respective interquartile ranges within the whole NAS--were associated with a 0.04 [95% confidence interval (CI), 0.00-0.08; p = 0.04] and 0.04 (95% CI, 0.00-0.08; p = 0.07) higher myoinositol-to-creatine ratio in the hippocampus. After accounting for patella bone lead declines over time, analyses adjusted for age showed that the effect of a 20-microg/g bone higher patella bone lead level doubled (0.09; 95% CI, 0.01-0.17; p = 0.03).

CONCLUSIONS

Cumulative lead exposure is associated with an increase in the myinositol-to-creatine ratio. These data suggest that, as assessed with MRS, glial effects may be more sensitive than neuronal effects as an indicator of cumulative exposure to lead in adults.

Using self-report measures in neurobehavioural toxicology: Can they be trusted?

Questionnaires are one of the most common methodologies used in research on neurobehavioural effects in occupational and environmental health, most commonly for gathering information on demographic characteristics, psychological or neurological symptoms, mood state, or exposure to hazards. Questionnaires are self-report measures, so by definition are subjective, although their degree of subjectivity depends on the phenomenon they are measuring. For some phenomena questionnaires are used because they are convenient but the information can be obtained from other sources. For other phenomena questionnaire or self-report is the only way of obtaining the information, for example, feelings and experiences, mood or emotions. Questionnaires are essential tools in psychological and neurobehavioural research as they can tap into aspects of nervous system function that cannot be readily measured in other ways. Despite the obvious need for self-report measures, there are a number of serious issues that threaten their validity as effective indicators of neurobehavioural function. This paper considers the implications of some of the major problems with self-report measures, focusing particularly on current approaches to measurement of symptoms and mood. It includes issues relating to validity of measures such as demand characteristics, malingering and under or over reporting, individual differences and problems of language and question style. It also includes issues relating to the interpretation of self-report measures, the relationship between self-report and performance measures, whether they reflect primary or secondary effects and whether they can be used as diagnostic criteria for neurobehavioural functional effects of occupational or environmental exposure. The paper looks at some of the current approaches to overcoming these problems including using interviews and observational methods and improving psychometric qualities of these measures. Self-report measures are important tools in our arsenal of measures of the neurobehavioural effects of occupational and environmental exposure, but they need to be used with care.

Memory Performance Profile in Occupational Chronic Solvent Encephalopathy Suggests Working Memory Dysfunction

This pilot study characterizes memory functioning of 11 men with occupational chronic solvent encephalopathy (CSE). Pattern (PRM) and spatial recognition (SRM), spatial span (SSP), spatial working memory (SWM), and paired associate learning (PAL) from Cambridge Neuropsychological Test Automated Battery were performed twice. The most sensitive variables to show impairment were PAL trials, SRM total correct, and SWM number of between-search errors. The majority of the CSE patients demonstrated mild deficits. The most persistent dysfunction was in tasks demanding working memory processing, which predicted well the CSE status. Qualitatively, the memory deficits resemble those seen in moderate or severe Parkinson's disease.

Cumulative lead exposure and cognitive performance among elderly men

BACKGROUND

Recent evidence suggests that cumulative lead exposure among adults in nonoccupational settings can adversely affect cognitive function. Which cognitive domains are affected has not been explored in detail.

METHODS

We used nonlinear spline regressions and linear repeated-measures analysis to assess the association between scores on a battery of cognitive tests over time and both blood and bone lead concentrations in the Normative Aging Study, a cohort of community-dwelling elderly men. Bone lead was measured from 1991 through 1999 with K-shell x-ray fluorescence. A total of 1089 men with a mean (+/-standard deviation) age of 68.7 (+/-7.4) years with blood lead measurements, 761 of whom also had valid bone lead measurements, completed at least one of a battery of cognitive tests. Approximately 3.5 years later, 69% of the men had at least one repeat test. Cognitive testing was performed from 1993 through 2001.

RESULTS

On a cross-sectional basis, there was little association between blood or bone lead and cognitive test scores. Change in performance over time on virtually all tests worsened as bone lead increased, with the most robust effects on performance and reaction time scores on visuospatial/visuomotor tests.

CONCLUSIONS

Low-level cumulative exposure to lead in nonoccupational settings may adversely affect cognitive function, particularly in the visuospatial/visuomotor domain.

Delta-aminolevulinic acid dehydratase polymorphism and the relation between low level lead exposure and the Mini-Mental Status Examination in older men: the Normative Aging Study

OBJECTIVE

To determine whether a polymorphism the in delta-aminolevulinic acid dehydratase (ALAD) gene modifies the neurotoxicity of lead in older adults.

METHODS

The authors studied men participating in the Department of Veterans Affairs' Normative Aging Study, assessing their recent exposure to lead by measuring blood lead (n = 915) at each triennial clinic visit, and, beginning in 1991, assessing their cumulative exposure by measuring lead levels in tibia (n = 722) and patella (n = 720), using K-shell x ray fluorescence. Starting in 1993 and again at each triennial visit, the authors administered the Mini-Mental State Examination (MMSE) to assess their cognitive functioning. The relation of the lead biomarkers to MMSE score was evaluated and this association was compared among men who carried the variant allele, ALAD-2, versus men without the allele.

RESULTS

Sixteen per cent of men carried the ALAD-2 allele. Median tibia and patella lead levels (first-third quartile) were 19 (13-28) and 27 (18-39) microg/g. Blood lead levels were consistent with non-occupational exposure: only 6% of men had levels > or =10 microg/dl. In multivariable adjusted analyses, higher levels of blood lead were associated with poorer performance on the MMSE. This association was most pronounced among ALAD-2 carriers, among whom a 3 microg/dl increment in blood lead (the interquartile range) was associated with a 0.26 point lower mean MMSE score (95% CI -0.54 to 0.01), compared with a 0.04 point lower score (95% CI -0.16 to 0.07) among non-carriers. The modest 0.22 point difference in these associations did not attain statistical significance, however (p(interaction) = 0.13). The associations between bone lead levels and MMSE score did not vary by ALAD-2 status.

CONCLUSIONS

Although not statistically significant, these findings suggest that ALAD genotype may modify blood lead's adverse association with cognition among older men who had community exposures to lead. However, despite a relatively large sample size and the use of sensitive methods for measuring lead burden, the evidence overall was fairly weak.

Prevalence of sensory and cognitive disabilities and falls, and their relationships: a community-based study

This study assessed the prevalence of sensory and cognitive disabilities and falls for various age groups, sexes, and socio-occupational categories, and their associations in the Lorraine population. The sample included 6,159 subjects, aged 15 years or more, randomly selected from the Lorraine population. They filled in a mailed questionnaire including socio-demographic characteristics, job, falls with physical injuries at the time of the survey, and sensory and cognitive disabilities. Data analysis was made via the adjusted odds ratios. The prevalences of sensory and cognitive disabilities were 3.0 and 4.7%, respectively, that of falls with physical injuries 2.4%: 1.2% for falls on the same level and 1.2% for falls to a lower level. Subjects aged over 70 were markedly affected, but the other age groups had relatively high prevalences as well; the workmen had the highest prevalence, followed by the foremen, farmers, craftsmen and tradesmen, and employees. A twofold risk independently of age, sex and job was found for the subjects with sensory or cognitive disabilities for all falls combined. These findings show the high prevalences of sensory and cognitive disabilities and falls with physical injuries, and their strong associations in the general population. Preventive measures are needed to detect and follow up the persons with these disabilities, limit their risk of falls and reduce occupational hazards.

Neurobehavioral changes of shipyard painters exposed to mixed organic solvents

This study was conducted to evaluate neurobehavioral changes arising from occupational exposure to organic solvents among shipyard painters and to establish whether a dose-effect relation existed where there was any observed impairment of neurobehavioral performance by running the test of Simple Reaction Time (SRT), Symbol Digit Substitution (SD), and Finger Tapping Speed (FT) with a computer-assisted neurobehavioral test battery. The study group consisted of 180 shipyard painters and 60 reference workers. The workers answered a self-administered questionnaire on occupational, medical history, and demographic characteristics including age, work duration, education level, and quantity and frequency of alcohol and smoking, and performed three psychometric tests on the Korean Computerized Neurobehavioral tests. To estimate cumulative exposure level, samples of ambient air on 61 painters were analyzed using a gas chromatograph. Shipyard painters and the reference group showed significant differences in the results of test of SD, FT of dominant hand, and FT of non-dominant hand. The test results of SD of shipyard painters also showed significant difference by duration of work. This suggests that occupational exposure of organic solvent could induce neurobehavioral changes in the shipyard painters. Therefore an objective neurobehavioral tests recommended on evaluating neurobehavioral performance of long-term solvent-exposed shipyard workers.

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.

Cumulative lead exposure and prospective change in cognition among elderly men: the VA Normative Aging Study

Lead exposure has been found to affect cognitive function in several different populations. Whether chronic low-level environmental exposure to lead results in cognitive decline among adults has not been examined. The authors assessed the relation between biomarkers of lead exposure and change in Mini-Mental State Examination (MMSE) scores in the Normative Aging Study, a cohort of elderly US men. Bone lead was measured with K-shell x-ray fluorescence. A total of 466 men aged 67.4 (standard deviation, 6.6) years took the MMSE on two occasions that were an average of 3.5 (standard deviation, 1.1) years apart during the period 1993-2001 and had bone lead concentrations measured during the period 1991-2002. A one-interquartile range (20 microg/g of bone mineral) higher patella bone lead concentration was associated with a change in MMSE score of -0.24 (95% confidence interval: -0.44, -0.05) after adjustment for age, education, smoking, alcohol intake, and time between MMSE tests. This effect is approximately equivalent to that of aging 5 years in relation to the baseline MMSE score in study data. The association with tibia lead was weaker and that with blood lead was absent. The data suggest that higher patella bone lead levels, a marker of mobilizable accumulated lead burden, are associated with a steeper decline over time in performance on the MMSE test among nonoccupationally exposed elderly men.