The impact of a two-year long COVID-19 public health restriction program on mechanical thrombectomy outcomes in a stroke network

OBJECTIVE

The purpose of this study was to evaluate the impact of COVID-19 pandemic public health restrictions on our drip and ship mechanical thrombectomy program in Santiago Chile.

MATERIALS AND METHODS

This was a retrospective analysis of a prospectively collected database comparing two cohorts, one during a two-year period before COVID-19 and the second during the two years of the pandemic at our metropolitan stroke program.

RESULTS

A total of 100 patients were included in the pre COVID-19 cohort (cohort 1) and 121 in the COVID-19 cohort (cohort 2). There was a significant difference between cohorts, with older patients, different occlusion sites and higher door to arterial puncture time during the COVID-19 period. A non-significant trend for worse 90-day outcomes and higher mortality was present in cohort 2. There were no statistical differences in safety treatment parameters.

CONCLUSIONS

COVID-19 pandemic has had a measurable impact on our mechanical thrombectomy program. Results showed similarities to other reported Latin American series, where less robust health systems could adapt less efficiently compared to developed countries. After two years of public health restrictions, there were changes in the treatment population characteristics, delay in some internal management metrics and a non-significant trend to worse 90-day outcomes and higher mortality.

Suboptimal Concentrations of Ceftazidime/Avibactam (CAZ-AVI) May Select for CAZ-AVI Resistance in Extensively Drug-Resistant Pseudomonas aeruginosa: In Vivo and In Vitro Evidence

This study correlates in vivo findings in a patient with an extensively drug-resistant (XDR) P. aeruginosa infection who developed resistance to ceftazidime-avibactam (CAZ-AVI) with in vitro results of a 7-day hollow-fiber infection model (HFIM) testing the same bacterial strain. The patient was critically ill with ventilator-associated pneumonia caused by XDR P. aeruginosa ST175 with CAZ-AVI MIC of 6 mg/L and was treated with CAZ-AVI in continuous infusion at doses adjusted for renal function. Plasma concentrations of CAZ-AVI were analyzed on days 3, 7, and 10. In the HIFM, the efficacy of different steady-state concentrations (Css) of CAZ-AVI (12, 18, 30 and 48 mg/L) was evaluated. In both models, a correlation was observed between the decreasing plasma levels of CAZ-AVI and the emergence of resistance. In the HIFM, a Css of 30 and 48 mg/L (corresponding to 5× and 8× MIC) had a bactericidal effect without selecting resistant mutants, whereas a Css of 12 and 18 mg/L (corresponding to 2× and 3× MIC) failed to prevent the emergence of resistance. CAZ/AVI resistance development was caused by the selection of a single ampC mutation in both patient and HFIM. Until further data are available, strategies to achieve plasma CAZ-AVI levels at least 4× MIC could be of interest, particularly in severe and high-inoculum infections caused by XDR P. aeruginosa with high CAZ-AVI MICs.

First multicenter experience using the Silk Vista flow diverter in 60 consecutive intracranial aneurysms: technical aspects

Background

The aim of this study was to assess the technical success and procedural safety of the new Silk Vista device (SV) by evaluating the intraprocedural and periprocedural complication rate after its use in several institutions worldwide.

Methods

The study involved a retrospective review of multicenter data regarding a consecutive series of patients with intracranial aneurysms, treated with the SV between September 2020 and January 2021. Clinical, intra/periprocedural and angiographic data, including approach, materials used, aneurysm size and location, device/s, technical details and initial angiographic aneurysm occlusion, were analyzed.

Results

60 aneurysms were treated with SV in 57 procedures. 66 devices were used, 3 removed and 63 implanted. The devices opened instantaneously in 60 out of 66 (91%) cases and complete wall apposition was achieved in 58 out of 63 (92%) devices implanted. In 4 out of 66 (6%) devices a partial opening of the distal end occurred, and in 5 (8%) devices incomplete apposition was reported. There were 3 (5%) intraprocedural thromboembolic events managed successfully with no permanent neurological morbidity, and 4 (7%) postprocedural events. There was no mortality in this study. The initial occlusion rates in the 60 aneurysms were as follows: O’Kelly–Marotta (OKM) A in 34 (57%) cases, OKM B in 15 (25%) cases, OKM C in 6 (10%) cases, and OKM D in 5 (8%) cases.

Conclusions

Our study demonstrated that the use of the new flow diverter Silk Vista for the treatment of intracranial aneurysms is feasible and technically safe.

Breaking the breach in Latin America: A pilot study of mechanical thrombectomy in the public healthcare system in Chile

BACKGROUND

Mechanical Thrombectomy (MT) is the standard of care for treatment of large vessel occlusion stroke. Until the beginning of 2020 MT was not funded nor widely implemented at the public healthcare level in Chile.

OBJECTIVE

To describe the results of a pilot program created to provide access to public MT in Santiago - Chile.

METHODS

Analysis from a prospectively collected database of MT cases performed between September 2017 and September 2019 in one center. A stroke network was developed with a single MT capable stroke center and five primary stroke centers. The primary efficacy endpoint was the rate of functional independence (mRS 0-2) at 90 days. Successful reperfusion was defined as 2 b-3 according to the thrombolysis in cerebral infarction scale. Safety outcomes include the rates of symptomatic intracranial hemorrhage and 90-day mortality.

RESULTS

A total of 100 patients were treated over the study period. Their mean age was 62.8 ± 11.8 years and median baseline National Institute of Health Stroke Scale (NIHSS) measurement was 17. Seventy-seven percent of the patients received intra venous thrombolysis. Successful reperfusion was achieved in 95% of the cases. NIHSS at 24 hours showed a median drop of 7 points from baseline (p < 0.00001) and 50% of the follow-up patients were functionally independent at 90 days. Symptomatic Intracerebral hemorrhage occurred in 5% of the patients and 90-day all case mortality was 11%.

CONCLUSIONS

We demonstrated the feasibility of a publicly funded MT program in Chile, with similar results as other international randomized control trials.

Quantitative evaluation of arteriovenous malformation hemodynamic changes after endovascular treatment using parametric color coding: A case series study

Background Brain arteriovenous malformations (AVMs) are complex vascular lesions. Endovascular treatment results are usually measured by calculating the volume reduction of the lesions. Nevertheless, vascular flow quantification seems a more physiologically accurate way of measuring endovascular results. We evaluated the use of parametric color coding (PCC) with digital subtraction angiography (DSA), in order to determine the feasibility of PCC to detect and measure the impact of AVM endovascular treatment-induced changes using real-time hemodynamic parameters. Methods and results Supratentorial brain AVM treatment was evaluated in 29 patients over the course of 38 sessions. Using regions of interest (ROIs) at the carotid siphon, arterial feeder, drainage vein and venous sinus, we found significant increase in time to peak (TTP) values at the arterial feeder, drainage vein and venous sinus. We compared TTP in four different embolization volume groups: I (0-25%), II (26-50%), III (51-75%) and IV (76-100%). We found significant differences between groups and a moderate correlation between embolization percentages, as well as an increase in TTP at the main vein ROI; but not in the arterial side or sinus. Conclusions Brain AVM endovascular treatment results can be quantified in vivo with PCC. PCC is capable of detecting hemodynamic changes after brain AVM endovascular treatment, that may reflect flow drop, and it is correlated with volume embolization.

Assessing social-emotional development in children from a longitudinal perspective

This paper provides an overview of methodological challenges related to the epidemiological assessment of social-emotional development in children. Because population-based studies involve large cohorts and are usually multicentre in structure, they have cost, participant burden and other specific issues that affect the feasibility of the types of measures that can be administered. Despite these challenges, accurate in-depth assessment of social-emotional functioning is crucial, based on its importance to child outcomes like mental health, academic performance, delinquency and substance abuse. Five dimensions of social-emotional development in children are defined: (1) social competence; (2) attachment; (3) emotional competence; (4) self-perceived competence; and (5) temperament/personality. Their measurement in a longitudinal study and associated challenges are discussed. Means of making valid, reliable assessments while at the same time minimising the multiple challenges posed in the epidemiological assessment of social-emotional development in children are reviewed.

Assessment of neuropsychological trajectories in longitudinal population-based studies of children

This paper provides a strategy for the assessment of brain function in longitudinal cohort studies of children. The proposed strategy invokes both domain-specific and omnibus intelligence test approaches. In order to minimise testing burden and practice effects, the cohort is divided into four groups with one-quarter tested at 6-monthly intervals in the 0-2-year age range (at ages 6 months, 1.0, 1.5 and 2.0 years) and at annual intervals from ages 3-20 (one-quarter of the children at age 3, another at age 4, etc). This strategy allows investigation of cognitive development and of the relationship between environmental influences and development at each age. It also allows introduction of new domains of function when age-appropriate. As far as possible, tests are used that will provide a rich source of both longitudinal and cross-sectional data. The testing strategy allows the introduction of novel tests and new domains as well as piloting of tests when the test burden is relatively light. In addition to the recommended tests for each age and domain, alternative tests are described. Assessment methodology and knowledge about child cognitive development will change over the next 20 years, and strategies are suggested for altering the proposed test schedule as appropriate.

Predictors of occupational exposure to styrene and styrene-7,8-oxide in the reinforced plastics industry

OBJECTIVE

To identify demographic and work related factors that predict blood levels of styrene and styrene-7,8-oxide (SO) in the fibreglass reinforced plastics (FRP) industry.

METHODS

Personal breathing-zone air samples and whole blood samples were collected repeatedly from 328 reinforced plastics workers in the Unuted States between 1996 and 1999. Styrene and its major metabolite SO were measured in these samples. Multivariable linear regression analyses were applied to the subject-specific levels to explain the variation in exposure and biomarker levels.

RESULTS

Exposure levels of styrene were approximately 500-fold higher than those of SO. Exposure levels of styrene and SO varied greatly among the types of products manufactured, with an 11-fold range of median air levels among categories for styrene and a 23-fold range for SO. Even after stratification by job title, median exposures of styrene and SO among laminators varied 14- and 31-fold across product categories. Furthermore, the relative proportions of exposures to styrene and SO varied among product categories. Multivariable regression analyses explained 70% and 63% of the variation in air levels of styrene and SO, respectively, and 72% and 34% of the variation in blood levels of styrene and SO, respectively. Overall, air levels of styrene and SO appear to have decreased substantially in this industry over the last 10-20 years in the US and were greatest among workers with the least seniority.

CONCLUSIONS

As levels of styrene and SO in air and blood varied among product categories in the FRP industry, use of job title as a surrogate for exposure can introduce unpredictable measurement errors and can confound the relation between exposure and health outcomes in epidemiology studies. Also, inverse relations between the intensity of exposure to styrene and SO and years on the job suggest that younger workers with little seniority are typically exposed to higher levels of styrene and SO than their coworkers.

Temporal association between serum prolactin concentration and exposure to styrene

BACKGROUND

Previous studies have suggested that occupational exposure to styrene is associated with increased serum levels of the anterior pituitary hormone prolactin (PRL).

AIMS

To test the hypotheses that: (1) the effect of styrene exposure on PRL secretion is an acute effect, not a subchronic or chronic effect; (2) blood styrene, as a measure of absorbed dose, is a stronger predictor of serum PRL level than personal breathing zone air styrene concentration.

METHODS

Subjects were recruited from 17 workplaces in the reinforced plastics industry. Personal breathing zone air styrene, whole blood styrene, and serum PRL were measured during one to three sessions, approximately one year apart. Linear multiple regression was used to model the relations between acute (air styrene or blood styrene obtained at same time as PRL), subchronic (average air or blood styrene over two or three sessions), and chronic (years of work in industry or facility times average air styrene over all sessions) indices of styrene exposure and serum PRL.

RESULTS

Acute blood styrene concentration was the strongest predictor of serum PRL concentration, with the model predicting a 2.06-fold increase in PRL (95% CI 1.11 to 3.84) for every 10-fold increase in blood styrene. Serum PRL tended to increase with increasing styrene exposure in both men and women; however, women tended to have higher PRL levels. For women, the change in blood styrene between sessions 1 and 2 was a significant predictor of the change in serum PRL between sessions.

CONCLUSIONS

Results confirm that styrene exposure enhances serum PRL concentrations and support an acute effect of styrene on PRL secretion.

Determination of styrene and styrene-7,8-oxide in human blood by gas chromatography-mass spectrometry

Methods of isotope-dilution gas chromatography-mass spectrometry (GC-MS) are described for the determination of styrene and styrene-7,8-oxide (SO) in blood. Styrene and SO were directly measured in pentane extracts of blood from 35 reinforced plastics workers exposed to 4.7-97 ppm styrene. Using positive ion chemical ionization, styrene could be detected at levels greater than 2.5 microg/l blood and SO at levels greater than 0.05 microg/l blood. An alternative method for measurement of SO employed reaction with valine followed by derivatization with pentafluorophenyl isothiocyanate and analysis via negative ion chemical ionization GC-MS-MS (SO detection limit=0.025 microg/l blood). The detection limits for SO by these two methods were 10-20-fold lower than gas chromatographic assays reported earlier, based upon either electron impact MS or flame ionization detection. Excellent agreement between the two SO methods was observed for standard calibration curves while moderate to good agreement was observed among selected reinforced plastics workers (n = 10). Levels of styrene in blood were found to be proportional to the corresponding air exposures to styrene, in line with other published relationships. Although levels of SO in blood, measured by the direct method, were significantly correlated with air levels of either styrene or SO among the reinforced plastics workers, blood concentrations were much lower than previously reported at a given exposure to styrene. The two assays for SO in blood appear to be unbiased and to have sufficient sensitivity and specificity for applications involving workers exposed to styrene and SO during the manufacture of reinforced plastics.

Serum hepatic biochemical activity in two populations of workers exposed to styrene

OBJECTIVE

To determine whether hepatic biochemical changes, as measured by routinely available tests indicative of hepatocellular necrosis, cholestasis, or altered hepatic clearance of bilirubin, occur in association with low to moderate exposure to styrene commonly experienced in industrial production.

METHODS

Two independent cross sectional studies were performed comparing serum hepatic transaminases (alanine aminotransferase (ALT) and aspartate aminotransferase (AST)), cholestatic enzymes (alkaline phosphatase (AP) and gamma glutamyl transpeptidase (GGT)), and bilirubin in (a) 47 workers of fibreglass reinforced plastics who were exposed to styrene and (b) 21 boat and tank fabricators, with separate referent groups of unexposed workers. Exposure to styrene was assessed in air by dosimetry, and in venous blood by headspace analysis. Hepatic biochemical variables were assessed across strata of exposure to styrene defined as 25 ppm in air, or 0.275 mg/l in blood, adjusting for age, sex, body mass index, and ethanol consumption.

RESULTS

A consistent and significant linear trend for increasing direct bilirubin and direct/total bilirubin ratio was found in association with increasing exposure to styrene, by both air and blood monitoring, in both studies. Mean direct bilirubin concentrations increased from 0.05-0.08 mg% in referents to 0.12-0.19 in workers exposed above 25 ppm, with a significant exposure-response trend (p<0.005). Significantly increased direct/total bilirubin ratios, ranging from 0.22 to 0.35 were associated with exposure to styrene (p<0.001), indicating diminished hepatic clearance of conjugated bilirubin. Also, a significant linear association between the hepatic transaminases ALT and AST and exposure to styrene was found in pooled regression analyses, with an increase in AP of about 10 IU/ml in workers exposed above 25 ppm air or 0.275 mg/l blood styrene in pooled analyses from both studies.

CONCLUSIONS

The consistent finding of increased direct bilirubin and AP concentrations in these two independent studies provides evidence for diminished hepatic clearance of conjugated bilirubin with associated cholestasis in workers exposed to styrene. The finding of a significant linear association between hepatic transaminase concentrations and exposure to styrene in pooled analyses is consistent with mild hepatic injury and associated metabolic dysfunction.

Measurement of styrene-7,8-oxide and other oxidation products of styrene in air

Styrene-7,8-oxide (SO) is generated at low concentrations from the oxidation of styrene during the processing of reinforced plastics. Since exposure to SO has important health implications, we developed air sampling and analytical methods to measure low levels of airborne SO in the presence of styrene and its other oxidation products, namely phenylacetaldehyde (PAA) and acetophenone (AP). Both active and passive air monitors were used. The active sampling method, which employed adsorption on Tenax, was suitable for measuring SO, PAA and AP but had limited capacity for styrene due to breakthrough. The passive monitor employed a carbon adsorbent and was suitable for measurement of styrene and SO but not PAA and AP due to poor recovery. After sampling, the analytes were extracted from the adsorbents with ethyl acetate and measured by gas chromatography with flame ionization detection or mass spectrometry. By maintaining the injection port at 70 degrees C, the thermal rearrangement of SO to PAA was minimized. Recovery of styrene and SO from the passive monitor depended upon loading and was corrected by linearization of the Freundlich isotherm. The limits of detection for SO, PAA, and AP were 0.2 ppb using the active monitor, and for SO was 1 ppb using the passive monitor. The sampling precision for SO (RSD from personal measurements) was 5.0% for the passive monitor and was 13.4% for the active monitor over a range of exposures from 5-150 ppb. The corresponding precision for styrene was 5.3% for the passive monitor for levels ranging from 1.2 to 104 ppm. Measurements of 235 personal exposures with the active monitor in 12 facilities manufacturing fiberglass-reinforced plastics (FRP) showed that levels of AP and PAA were below 7.8 ppb and 5 ppb, respectively. In contrast, SO averaged 30.4 ppb (SE=2.4) in these FRP facilities, ranging from below 0.2 ppb to 190 ppb. The active monitor was also used to detect airborne SO at levels of approximately equals 1 ppb in one facility manufacturing styrene butadiene rubber, suggesting that SO is generally present during the polymerization of styrene. Personal passive monitoring in the 12 FRP facilities (n = 657) revealed mean concentrations of styrene ranging between 1.8 and 55.4 ppm, and for SO between 1.7 and 62.6 ppb. The ratio of the mean styrene level to the mean SO level varied between 449:1 and 1,635:1 among the 12 FRP facilities.

Occupational exposure to electromagnetic fields and Alzheimer disease

The association between occupational exposure to electromagnetic fields (EMF) and Alzheimer disease (AD) was examined. Subjects were identified from a large health maintenance organization in Seattle, Washington, and matched by age, sex, and proxy type. A complete occupational history was obtained from proxies and controls. Following the interview, two industrial hygienists (IHs) rated exposures to EMF for each job blinded to case-control status. Exposures to EMF were rated as probable intermittent exposure or probable exposure for extended periods to levels above threshold. Conditional logistic regression was used to calculate the risk of AD given EMF exposure stratified by IH. The odds ratios for ever having been exposed to EMF were 0.74 [95% confidence interval (CI) 0.29-1.92] and 0.95 (95% CI 0.27-2.43) for each IH, adjusting for age and education. No dose-response effect was noted. Agreement between the two IHs for ever having been exposed to EMF was good (kappa = 0.57, p < 0.0001). This study was unable to support an association between EMF and AD.

Occupational exposures to solvents and aluminium and estimated risk of Alzheimer's disease

OBJECTIVES

To study the role of occupational exposures to solvents and aluminium in the aetiology of Alzheimer's disease (AD). An industrial hygienist rated exposure.

METHODS

89 subjects diagnosed with probable AD were matched by age, sex, and type of informant to 89 controls. Subjects were identified from a large health maintenance organisation in Seattle, WA. A complete occupational history was obtained from spouses of cases and controls as well as from controls themselves. After the interview an industrial hygienist, blinded to case-control status, rated exposures.

RESULTS

Non-significant associations were found between AD and ever having been occupationally exposed to solvents (odds ratio (OR) 1.77, 95% confidence interval (95% CI) 0.81 to 3.90) and aluminium (OR 1.46, 95% CI 0.62 to 3.42). Although an increasing risk was found with increasing number of years of exposure to solvents, there was an inverse association between exposure intensity and AD, and measures of cumulative exposure taking into account both intensity and duration of exposure were not significant. Analysis of the age at which half the cumulative exposure to solvents was achieved showed that an older age incurred a greater risk of AD than a younger age. However, the total amount of exposure carried no risk.

CONCLUSIONS

The results suggest that lifetime occupational exposure to solvents and aluminium are not likely to be important risk factors for Alzheimer's disease.

Neurobehavioral effects from exposure to dental amalgam Hg(o): new distinctions between recent exposure and Hg body burden

Potential toxicity from exposure to mercury vapor (Hg(o)) from dental amalgam fillings is the subject of current public health debate in many countries. We evaluated potential central nervous system (CNS) toxicity associated with handling Hg-containing amalgam materials among dental personnel with very low levels of Hg(o) exposure (i.e., urinary Hg <4 microg/l), applying a neurobehavioral test battery to evaluate CNS functions in relation to both recent exposure and Hg body burden. New distinctions between subtle preclinical effects on symptoms, mood, motor function, and cognition were found associated with Hg body burden as compared with those associated with recent exposure. The pattern of results, comparable to findings previously reported among subjects with urinary Hg >50 microg/l, presents convincing new evidence of adverse behavioral effects associated with low Hg(o) exposures within the range of that received by the general population.

Behavioral effects of low-level exposure to Hg0 among dental professionals: a cross-study evaluation of psychomotor effects

A Across-study design was used to evaluate the sensitivities of five psychomotor tasks previously used to assess preclinical effects of low-level Hg0 (urinary < or =55 microg/l). Pooling dental professional subject populations from six studies conducted over the last 6 years, a larger study population was obtained with a high degree of uniformity (N = 230). The five psychomotor tests were: Intentional Hand Steadiness Test (IHST); Finger Tapping: The One-Hole Test: NES Simple Reaction Time (SRT); and Hand Tremor. Multivariate analyses were conducted following the hierarchical analysis of multiple responses (HAMR) approach. First, multiple scores of each test were combined into a single-factor (or related summary) variable and its reliability was estimated. Second. multiple regression analyses were conducted including log-transformed [Hg0]U levels, age, gender, and alcohol consumption in each model. Computed were both B and bu, the magnitudes of the log-Hg0 standardized coefficient. respectively uncorrected and corrected for dependent variable attenuation due to unreliability. Results indicated remarkable differences in the effects of relative level of Hg0 on psychomotor performance. Significant associations were found for the IHST factor (B = 0.415, p < 10(-6)), followed by finger tapping, which was relatively meager and insignificant (B 0.141, p = 0.17). The IHST results hold the greatest occupational relevance for dental professionals who rely on manual dexterity in restorative dentistry. Further, this statistical approach is recommended in future studies for condensation of multiple scores into summary scores with enhanced reliabilities useful in correcting for attenuation relationships (B(u)s) with exposure levels.

Epidemiologic assessment of measures used to indicate low-level exposure to mercury vapor (Hg)

Mercury (Hg) concentrations in individual spot urine samples collected over consecutive 1-d periods were compared with Hg concentrations measured in combined 24-h urine samples from 69 practicing dental professionals with low exposure to Hg vapor (Hg) in order to validate the use of spot urine samples as an indicator of Hg exposure. The level of Hg in air as an exposure measure was also evaluated by comparing air concentrations of Hg in dental offices with both spot and 24-h urine Hg levels. The results showed: (1) There was little diurnal variation (approximately 9%) in urinary Hg values; (2) a strong correlation (R2 = .85) exists between the Hg concentration in the first morning void and that in a complete 24-h urine sample; (3) adjustment of urinary Hg levels for creatinine concentrations did not improve this correlation; (4) there was no added value in the speciation of total urinary Hg into the inorganic Hg fraction; and (5) concentrations of Hg in air did not significantly correlate with measures of Hg in urine at this low Hg exposure level. We conclude from this study that first morning void urine samples may be used to derive reasonably valid estimates of Hg concentrations found in the total amount of urine collected over a 24-h period. Thus, due to its comparability, ease of collection, and lower cost, the first morning urine void may be used in place of a sample collected over a full 24 h to facilitate Hg exposure assessments in epidemiologic studies that use urinary Hg levels as a measure of low-level Hg exposure.

Analyzing multivariate neurobehavioral outcomes in occupational studies: a comparison of approaches

Neurobehavioral studies often employ test batteries and confront issues of multiple testing and comparability between batteries. We have organized our battery of 12 tests into areas of neurobehavioral function to reduce the number of reported results, provide greater statistical power, and improve interpretability of the results. We explored several different organizational and statistical methods of creating summary scores including a priori groupings based upon clinical experience and factor analysis. We compared the sensitivity of these summary scores to performance changes associated with exposure to styrene in the manufacture of reinforced plastics. Our results demonstrated dramatic increases in power to detect exposure related changes compared to using individual test scores. Furthermore, the various methods provided generally compatible and comparable results. We encourage other neurobehavioral investigators to pursue and refine this approach.

Effect of overtime work on cognitive function in automotive workers

OBJECTIVE

The present investigation examined whether increased overtime work predicts impairment in cognitive performance in the domains of attention, executive function, and mood.

METHODS

The behavioral and cognitive functions of 248 automotive workers were measured by a neurobehavioral test performance. Overtime, defined as number of hours worked greater than 8 h a day or greater than 5 d a week, was calculated from company payroll records for the week before the test day. The number of consecutive days worked before the test day was also determined.

RESULTS

Cross-sectional data analysis by multiple linear regression, after adjustment for the effects of age, education, gender, alcohol intake, repeated grade in school, acute petroleum naphtha exposure, shift worked, job type, number of consecutive days worked before the test day, and number of hours worked on the test day before the testing, demonstrated that increased overtime was significantly associated with impaired performance on several tests of attention and executive function. Increased feelings of depression, fatigue, and confusion were also associated with increased overtime work. In addition significant interaction effects were observed for job type but not for naphtha exposure.

CONCLUSIONS

The findings support the hypothesis that overtime work results in impaired cognitive performance in the areas of attention and executive function and that both overtime hours and the number of consecutive days worked prior to a test day affect mood.

Hepatic ultrasonic changes in workers exposed to perchloroethylene

OBJECTIVE

To determine if subclinical hepatotoxicity is associated with exposure to perchloroethylene at concentrations commonly experienced in the workplace, and whether surveillance with serum hepatic transaminase activity underestimates such effects.

METHODS

Hepatic parenchymal echogenicity on ultrasonography and serum hepatic transaminase activity were compared in 29 community based dry cleaning operators exposed to perchloroethylene, and a control group of 29 non-exposed laundry workers. Perchloroethylene exposure was assessed by work history and air monitoring.

RESULTS

Mean hepatic transaminase activities were minimally increased in dry cleaners compared with laundry workers. Increased alanine aminotransferase activities, between 1.0 and 1.5 times the normal limits, were found in five of 27 (19%) dry cleaners compared with one of 26 (4%) laundry workers. In contrast, diffuse parenchymal changes in echogenicity, as determined by hepatic ultrasonography, were increased nearly twofold in dry cleaners, occurring in 18 of 27 (67%) dry cleaners compared with 10 of 26 (39%) laundry workers (P < 0.05), and were most strongly associated with increased perchloroethylene exposure in older dry to dry or wet transfer operations (odds ratio 4.2, 95% confidence interval 1.1-15.3). Mean eight hour time weighted average perchloroethylene exposure for dry cleaners was 16 ppm, which is less than the permissible exposure limit of 100 ppm in the United States.

CONCLUSIONS

It was concluded that mild to moderate hepatic parenchymal changes occur more frequently in workers exposed to perchloroethylene than in populations not exposed to chemical solvents, and that these effects are underestimated by serum hepatic transaminase activity.

Neurobehavioral effects of acute and chronic mixed-solvent exposure in the screen printing industry

This 2-year prospective study examined the neurobehavioral effects of acute and chronic exposure to mixed solvents in workers in a screen printing business. A total of 30 subjects participated in the study in two field testings over a 12 month period. Each subject completed a detailed medical and occupational questionnaire, had a neurological examination, and underwent a battery of neuropsychological tests. Industrial hygiene investigation identified the following chemical exposures as present: toluene, methyl ethyl ketone, mineral spirits, beta-ether, methylene chloride, and acetic acid. Different departments and jobs had varying degrees of exposure to these chemicals, the highest exposures being in the ink mix area and the screen washroom area. However, all exposure levels were below recommended threshold limit values. Persons categorized as having higher acute exposure demonstrated significantly impaired test performance on tasks involving manual dexterity, visual memory, and mood. Those with higher chronic exposure demonstrated significantly poorer performance on visual memory tasks and mood. Results suggest that the mixed solvents used in the screen printing industry have an effect on central nervous system functioning in the absence of obvious clinical disease.

A behavioral evaluation of PCE exposure in patients and dry cleaners: a possible relationship between clinical and preclinical effects

Long-term deficits in visuospatial function and memory and disturbances in mood have been clinically identified and followed in four patients occupationally exposed to perchloroethylene (PCE). A frontal/limbic hypothesis is offered as the site of pathology. A separate study among 65 dry cleaners was conducted to provide similar evidence of impairment, suggesting a continuum between clinical and preclinical effects. Three exposure zones were identified for the counter clerks, pressers, and operators corresponding to air levels of 11.2, 23.2, and 40.8 ppm. Decrements were found for visual reproductions (14.4%), the number correct (6.7%) and the latency (10%) for pattern memory, and the number correct (3.9%) for pattern recognition. Chronic, life-long deficits appear below 50 ppm and require at least 3 years of exposure. A reexamination of the OSHA standard is recommended and shows that behavioral testing can be used as an early indicator of more serious clinical effects.

Behavioral effects of low-level exposure to elemental Hg among dentists

Exposure thresholds for health effects associated with elemental mercury (Hg degree) exposure were examined by comparing behavioral test scores of 19 exposed (mean urinary Hg = 36 micrograms/l) with those of 20 unexposed dentists. Thirty-six micrograms Hg/l is 7 times greater than the 5 micrograms Hg/l mean level measured in a national sample of dentists. To improve the distinction between recent and cumulative effects, the study also evaluated porphyrin concentrations in urine, which are correlated with renal Hg content (a measure of cumulative body burden). Subjects provided an on-site spot urine sample, were administered a 1-h assessment consisting of a consent form, the Profile of Mood Scales, a symptom and medical questionnaire, and 6 behavioral tests: digit-span, symbol-digit substitution, simple reaction time, the ability to switch between tasks, vocabulary, and the One Hole Test. Multivariate regression techniques were used to evaluate dose-effects controlling for the effects of age, race, gender and alcohol consumption. A dose-effect was considered statistically significant below a p value of 0.05. Significant urinary Hg dose-effects were found for poor mental concentration, emotional lability, somatosensory irritation, and mood scores. Individual tests evaluating cognitive and motor function changed in the expected directions but were not significantly associated with urinary Hg. However, the pooled sum of rank scores for combinations of tests within domains were significantly associated with urinary Hg, providing evidence of subtle preclinical changes in behavior associated with Hg exposure. Coproporphyrin, one of three urinary porphyrins altered by mercury exposure, was significantly associated with deficits in digit span and simple reaction time.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium 2,3-dimercaptopropane-1-sulfonate challenge test for mercury in humans: II. Urinary mercury, porphyrins and neurobehavioral changes of dental workers in Monterrey, Mexico

The sodium salt of 2,3-dimercaptopropane-1-sulfonic acid (DMPS) challenge test (300 mg p.o. after an 11-hr fast) was given in Monterrey, Mexico to dental and nondental personnel. Urine samples were collected and analyzed for total mercury. The mean mercury urinary excretion (+/- S.E.) for 6 hr before and 6 hr after DMPS administration for 10 dental technicians, who formulate amalgam, was 4.84 micrograms +/- 0.742 and 424.0 micrograms +/- 84.9; for 5 dentists, who use amalgam in their practice, 3.28 micrograms +/- 1.11 and 162.0 micrograms +/- 51.2; and for 13 nondental personnel, 0.783 microgram +/- 0.189 and 27.3 micrograms +/- 3.19. The urinary coproporphyrin levels before DMPS administration, which are indicative of renal mercury content, were quantitatively associated with the urinary mercury levels among the three study groups after DMPS administration. This was not so if the urinary mercury level before DMPS administration was compared with the urinary coproporphyrin concentration. The urinary mercury level after DMPS administration is a better indicator of exposure and renal mercury burden than is the mercury level measured in the urine before DMPS is given. Regression analysis showed that the coefficient of urinary mercury was statistically and adversely associated with complex attention (switching task), the perceptual motor task (symbol-digit substitution), symptoms and mood. The easily performed DMPS-mercury challenge test is useful for monitoring dental personnel for mercury vapor exposure.

Platelet monoamine oxidase B activity in workers exposed to styrene

A cross-sectional study was conducted to evaluate monoamine oxidase type B (MAO-B) activity in platelets as a biomarker of effect of styrene and perchloroethylene exposures. MAO-B is an enzyme system involved in dopamine catabolism, the impairment of which has been postulated as a mechanism of styrene-induced neurotoxicity. We previously observed an inverse association between blood styrene and MAO-B among reinforced plastics manufacturing workers. The present study included 59 male boat plant workers exposed to styrene (exposure range < 1-144 ppm, 8-h TWA). Two comparison groups comprised six male dry cleaning workers exposed to perchloroethylene (PCE; exposure range < 2-37 ppm) and 14 male laundry workers not exposed to either agent. Respiratory protection was not used by any of the styrene- or PCE-exposed workers; thus, air concentrations were regarded as valid exposure indicators. MAO-B activity (pmol/10(8) cells/h) was measured in peripheral blood platelets, using phenylethylamine as substrate. Only small overall mean differences in MAO-B were observed among the three groups; mean values were 4.21, 4.51, and 4.12 for the styrene-exposed, PCE-exposed, and laundry workers, respectively. Despite the absence of gross differences among the groups, styrene exposure was inversely related to MAO-B. Mean values for four increasing exposure group quartiles were: 5.60, 4.13, 3.69, and 3.44. The Spearman rank correlation coefficient for styrene with MAO-B was -0.41. Adjustment for age, medication use, smoking, and alcohol consumption had only a minimal effect on this trend.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuropsychological effects of exposure to naphtha among automotive workers

The association between exposure to naphtha and neurobehavioural measures was examined prospectively over one year among workers employed at an automotive plant that used naphtha to calibrate fuel injectors. The neurobehavioural tests included those that assess mood, basic intelligence, and functioning of the cerebral frontal lobes and limbic system and were designed so that acute, reversible, and chronic effects of solvent exposure could be assessed. Participants were 248 workers in June 1988, and the testing was repeated on 185 of these workers in 1989. Concentrations of naphtha at the plant ranged from six to 709 mg/m3, although exposure was greater in 1988 than in 1989. Duration of exposure for individual subjects ranged from 0.8 to 7.3 years. Cross sectional data analyses showed significant associations between level of exposure to naphtha and slower timed scores on trails A, and greater reports of negative affective symptoms on profile of mood states scales in 1988 but not 1989. Threshold model analyses of the 1989 data showed an association between score on visual reproductions immediate recall and daily exposure to naphtha at or above 1050 h x mg/m3. Models of chronic exposure showed no associations between chronic exposure and negative neurobehavioural outcome. Results suggest that naphtha produces mild acute reversible effects on function of the central nervous system at or above daily exposures of 540 h x mg/m3 (approximately 90 ppm/h).

Urinary porphyrin profiles as a biomarker of mercury exposure: studies on dentists with occupational exposure to mercury vapor

Porphyrins are formed as intermediates in the biosynthesis of heme. In humans and other mammals, porphyrins with eight, seven, six, five, and four carboxyl groups are excreted in the urine in a well-established pattern. Mercury selectively alters porphyrin metabolism in kidney proximal tubule cells, leading to an altered urinary porphyrin excretion pattern. Previous studies in rats have shown that changes in the urinary porphyrin profile during exposure to mercury as methylmercury hydroxide are uniquely characterized by highly elevated (20- to 30-fold) levels of four- and five-carboxyl porphyrins and by the excretion of an atypical porphyrin ("precoproporphyrin"), which elutes on high performance liquid chromatography (HPLC) approximately midway between penta- and coproporphyrins. Changes in the urinary porphyrin profile are highly correlated with the dose and duration of mercury exposure and persist for up to 20 wk following cessation of mercury treatment. In the present studies, the utility of urinary porphyrin profile changes as a biomarker of mercury exposure in human subjects was evaluated. Urinary porphyrin concentrations were measured in dentists participating in the Health Screening Programs conducted during the 1991 and 1992 annual meetings of the American Dental Association and compared with urinary mercury levels measured in the same subjects. Among dentists with no detectable urinary mercury, mean concentrations of urinary porphyrins were within the established normal ranges for male human subjects. In contrast, among dentists with urinary mercury in excess of 20 micrograms/L, mean urinary concentrations of four- and five-carboxyl porphyrins as well as of precoproporphyrin were elevated three to four times those of unexposed subjects. Significant differences in urinary porphyrin concentrations remained when porphyrin concentrations in spot urine samples were adjusted for creatinine levels. These findings suggest that urinary porphyrin profiles may serve as a useful biomarker of mercury exposure in clinical or epidemiologic studies of mercury-related human health risks.

Estimation of cumulative exposures to naphtha at an automobile fuel-injector manufacturing plant

As part of an epidemiologic study of neuropsychological and renal effects of occupational exposure to organic solvents, estimates of cumulative exposure to naphtha were derived for workers at an automobile fuel-injector manufacturing plant. The approach to exposure estimation was relatively unusual in three respects: (1) a marked association between indoor naphtha air concentration and outdoor temperature was modeled and applied to detailed historical temperature data to calculate cumulative exposure estimates; (2) the large number of investigator-generated air samples allowed the use of analyses of variance to compare alternative job-grouping schemes; and (3) the young age of the plant and few process changes allowed for historical exposure estimates with a high degree of confidence. The derived estimates of cumulative exposure appear to offer a firm basis for epidemiologic analyses of exposure-health outcome relationships.

Renal effects of naphtha exposure among automotive workers

As part of a study on health effects of naphtha exposure, the association between naphtha exposure and urinary excretion of total protein, albumin, beta-N-acetyl-D-glucosaminidase (beta-NAG), and beta 2-microglobulin was assessed prospectively over 1 year among workers at an automotive plant that used naphtha to calibrate fuel injectors. Participants consisted of 248 workers who provided spot urine samples in June 1988 among whom 181 workers provided specimens again in June 1989. Naphtha air concentrations at the plant ranged from 6 to 790 mg/m3 and the length of exposure ranged from 0.8 to 7.3 years. In both 1988 and 1989, the overall distribution of the four measures of renal function appeared consistent with that of an unexposed population. In cross-sectional analyses, there were no statistically significant associations in the expected direction between cumulative or recent naphtha exposure and the measures of renal function. In longitudinal analyses, the change in beta-NAG was positively associated with the change in recent naphtha exposure (P = .009). The effect of the naphtha exposure during 1 workweek was assessed among 17 workers who provided urine samples Monday preshift, Monday postshift, and Friday postshift. No associations were found. The results of this study do not provide strong evidence of naphtha-associated renal effects at these levels of exposure.

Acute behavioural comparisons of toluene and ethanol in human subjects

A comparison of toluene and ethanol (EtOH) induced changes in central nervous system (CNS) function and symptoms were evaluated in two studies, and when possible the effects of toluene were expressed in EtOH equivalent units. The toluene concentrations were 0, 75, and 150 ppm, bracketing the American Conference of Governmental Industrial Hygienists threshold limit value (ACGIH TLV) of 100 ppm. The socially relevant EtOH doses were 0.00, 0.33, and 0.66 g EtOH/kg body weight, equivalent to two and four 3.5% 12 ounce beers. Forty two paid college students were used in each study. In the first study, subjects were exposed to toluene and an odour masking agent menthol (0.078 ppm) for seven hours over three days. In the second study EtOH or a placebo was administered at 1530 across three days also in the presence of menthol. Verbal and visual short term memory (Sternberg, digit span, Benton, pattern memory), perception (pattern recognition), psychomotor skill (simple reaction time, continuous performance, symbol-digit, hand-eye coordination, finger tapping, and critical tracking), manual dexterity (one hole), mood (profile on mood scales (POMS), fatigue (fatigue checklist), and verbal ability were evaluated at 0800, 1200, and 1600. Voluntary symptoms and observations of sleep were collected daily. A 3 x 3 latin square design evaluated solvent effects simultaneously controlling for learning and dose sequence. An analysis of variance and test for trend were performed on am-pm differences reflecting an eight hour workday and on pm scores for each solvent, in which subjects were their own control Intersubject variation in absorbance was monitored in breath. A 5 to 10% decrement was considered meaningful if consistent with a linear trend at p less than 0.05. At 150 ppm toluene, losses in performance were 6.0% for digit span, 12.1% for pattern recognition (latency), 5% for pattern memory (number correct), 6.5% for one hole, and 3% for critical tracking. The number of headaches and eye irritation also increased in a dose-response manner. The greatest effect was found for an increasing number of observations of sleep. A range of 2 to 7% decrements suggest the ACGIH TLV of 100 ppm toluene may be a good estimate of the biological threshold supporting a re-evaluation of the TLV. At 0.66 g EtOH/kg body weight symptoms and performance decrements were 6.6% for digit span, 9.2% for pattern recognition, 4.0% for continuous performance, 7.9% for symbol-digit, 16.5% for finger tapping, 6.2% for critical tracking, and 5.2% for the one hole test. The EtOH equivalents at 150 ppm toluene for digit span (0.56g EtOH/kg/body weight), the latency for pattern recognition (0.66 g EtOH kg body weight), and the one hole element "move" (0.37 g EtOH kg body weight) show that the first two measures would be affected at or above the 50 mg% blood alcohol concentration. This concentration is recognised as the lowest alcohol concentration associated with increased numbers of automobile accidents. The results suggest that EtOH may be a useful acute standard to compare the effects of various industrial solvents and support investigating an association between exposure to solvents and increased risk to safety in industry.

Acute neurobehavioural effects of toluene

An acute inhalation chamber study of 42 college students was performed to investigate the relation between exposure to 0, 75, and 150 ppm of toluene and changes in central nervous system function and symptoms. Paid subjects were exposed for seven hours over three days. Verbal and visual short term memory (Sternberg, digit span, Benton, pattern memory); perception (pattern recognition); psychomotor skill (simple reaction time, continuous performance, digit symbol, hand-eye coordination, finger tapping, and critical tracking); manual dexterity (one hole); mood (profile of mood scales (POMS]; fatigue (fatigue checklist); and verbal ability were evaluated at 0800, 1200, and 1600 hours. Voluntary symptoms and observations of sleep were collected daily. An analysis of variance and test for trend was performed on the difference and score for each concentration reflecting an eight hour workday where each subject was their own control. A 3 x 3 Latin square study design evaluated toluene effects simultaneously, controlling for learning across the three days and the solvent order. Intersubject variation in solvent uptake was monitored in breath and urine. A 5-10% decrement in performance was considered significant if it was consistent with a linear trend at p less than 0.05. Adverse performance at 150 ppm toluene was found at 6.0% for digit span, 12.1% for pattern recognition (latency), 5.0% for pattern memory (number correct), 6.5% for one hole, and 3.0% for critical tracking. The number of headaches and eye irritation also increased in a dose response manner. The greatest effect was found for an increasing number of observations of sleep. Overall, no clear pattern of neurobehavioural effects was found consistent with the type 1 central nervous system as classified by the World Health Organisation. Subtle acute effects, however, were found just below and above the ACGIH TLV of 100 ppm toluene, supporting the position that the guideline be lowered since the biological threshold of behavioural effects may be comparable with the TLV.

Increase in the size of soluble brain adenylate cyclase with activation by guanosine 5'-(beta, gamma-imino)triphosphate

Adenylate cyclase solubilized from bovine brain with Lubrol 12A9 or Triton X-100 can be resolved into two forms by gel filtration or sucrose density gradient centrifugation. The activity of one of these forms is not stimulatable by guanosine 5'-(beta, gamma-imino)triphosphate (Gpp(NH)p) and represents the "basal" adenylate cyclase activity. In Lubrol 12A9, this form has Mr = 330,000 (total, protein and detergent) and Mr (protein only) = 265,000. The other form of adenylate cyclase can be activated by Gpp(NH)p and has a smaller molecular weight: Mr (protein and detergent) = 293,000, Mr (protein only) = 199,000. Upon activation by Gpp(NH)p, the size of the Gpp(NH)p-responsive form of adenylate cyclase increases: Mr (protein and detergent) = 330,000, Mr (protein only) = 251,000. Similar values were obtained in Triton X-100. The kinetics of heat inactivation are different in the two forms of the enzyme. Both forms are activated about 2-fold by 5 mM MnCl2. Neither of the forms is associated with measurable low Km GTPase activity. On the basis of these studies, we propose that the catalytic unit (C) of adenylate cyclase and the guanine nucleotide regulatory unit (G/F) may exist in solution in the following rapid equilibrium: (formula: see text) We propose that activation by Gpp(NH)p stabilizes the C . G/F complex and this accounts for the greater mass of the enzyme measured after activation with Gpp(NH)p. The size of the enzyme which represents the basal activity is very similar to that of the C . G/F complex. We suggest, therefore, that the basal activity is the result of a stable association of the catalytic unit with the guanine nucleotide regulatory site.