I A Calvert

Neuropsychological effects of long-term exposure to organophosphates in sheep dip.

Organophosphate-based pesticides are widely used throughout the world. The acute effects of over-exposure to such compounds are well known. Concern has also been expressed that long-term exposure may result in damage to the nervous system. In a cross-sectional study, we compared neuropsychological performance in 146 sheep farmers who were exposed to organophosphates in the course of sheep dipping with 143 non-exposed quarry workers (controls). The farmers performed significantly worse than controls in tests to assess sustained attention and speed of information processing. These effects remained after adjustment for covariates. The farmers also showed greater vulnerability to psychiatric disorder than did the controls as measured by the General Health Questionnaire. There were no observed effects on short-term memory and learning. Repeated exposure to organophosphate-based pesticides appears to be associated with subtle changes in the nervous system. Measures should be taken to reduce exposure to organophosphates as far as possible during agricultural operations.

Abnormalities on neurological examination among sheep farmers exposed to organophosphorous pesticides

OBJECTIVES: Organophosphates are effective pesticides which are frequently used in several agricultural settings. Although their acute effects are well characterised, it remains unclear whether long term exposure can damage the human nervous system. This study sought to investigate their long term effects by comparing abnormalities on neurological examination between groups of workers exposed to organophosphates and an unexposed group. METHODS: 146 exposed sheep farmers and 143 unexposed quarry workers were recruited into a cross sectional study of symptoms and neuropsychological effects of long term exposure to organophosphates in sheep dip. From a symptom questionnaire given immediately after dipping the 10 most symptomatic and 10 least symptomatic farmers were selected. Several months later each of these, along with 10 of the unexposed quarry workers, underwent a standardised neurological examination similar to that which might be used in clinical practice, at at time as remote as possible from recent exposure to organophosphates so as to exclude any acute effects. RESULTS: All 30 selected subjects agreed to participate. The components of the examination which showed a significant difference were two point discrimination on the dorsum of the hand (symptomatic farmers 22 mm; asymptomatic farmers 13 mm; quarry workers 8 mm) and the dorsum of the foot (symptomatic farmers 34 mm; asymptomatic farmers 10 mm; quarry workers 11 mm), and mean calf circumference (symptomatic farmers 35.0 cm; asymptomatic farmers 36.3 cm; quarry workers 38.6 cm). Overall the prevalence of neurological abnormalities was low. CONCLUSIONS: The differences in neurological examination detected between groups were subtle and their clinical significance was unclear. However, they do suggest evidence of an adverse neurological effect from exposure to organophosphates. Further, larger scale studies will be required before it is possible to confirm or refute the differences detected.

Respiratory health effects of carbon black: a survey of European carbon black workers.

A study population of 3086 employees was identified in 18 carbon black production plants in seven European countries. Respiratory health questionnaires, spirometry, and chest radiographs were used to estimate effects on health and personal monitoring procedures were employed to measure current exposure to inspirable and respirable dust along with sulphur and carbon monoxide. The low concentrations of gaseous contaminants made the generation of their current and cumulative exposure indices impossible. Low responses from some plants restricted the final analysis to 1742 employees in 15 plants (81% response rate) for respiratory symptoms and spirometry, and 1096 chest radiographs from 10 plants (74% response rate). In total, 1298 respirable and 1317 inspirable dust samples, as well as 1301 sulphur dioxide and 1322 carbon monoxide samples were collected. This study is the first to include a comprehensive and concurrent assessment of occupational exposure to carbon black dust and its associated gaseous contaminants. Cough, sputum, and the symptoms of chronic bronchitis were found to be associated with increasing indices of current exposure. Lung function tests also showed small decreases in relation to increasing dust exposure in both smokers and non-smokers. Nearly 25% of the chest radiographs showed small opacities of category 0/1 or greater. These were strongly associated with indices of cumulative dust exposure. The findings are consistent with a non-irritant effect of carbon black dust on the airways combined with dust retention in the lungs. Further cross sectional studies are planned to investigate whether long term exposure to carbon black dust causes damage to the lung parenchyma.

Efficiency of different grouping schemes for dust exposure in the European carbon black respiratory morbidity study

OBJECTIVES: The aim of this study was to assess the theoretical efficiencies of different grouping strategies and its effect on the exposure-response relation in a study of respiratory morbidity associated with exposure to total inhalable and respirable carbon black dust. METHODS: A large epidemiological study is being undertaken to investigate the respiratory health of employees in the European carbon black manufacturing industry in relation to exposure to carbon black dust. In phase 2 of the study, repeated measurements of total inhalable and respirable dust were taken which enabled estimation of various components of variability in the exposure data (within and between worker variance and within and between group variance). These variance components were used to calculate the contrast in exposure between the groups in various classification schemes and to calculate the theoretical attenuation of the exposure-response relation and the standard error (SE) of the slope. RESULTS: High contrast in exposure was found when workers were classified according to the combination of their factory and job category as well as when these combinations were amalgamated into five exposure groups. Attenuation was minimal with most grouping schemes; only with the individual based strategy was the attenuation large. The SE of the theoretically attenuated exposure-response slope was smallest for the strategy based on individual people followed by the classification scheme based on factory and job category. CONCLUSIONS: It was concluded that, although some assumptions for the calculations of the attenuation of the exposure-response slope were not met, the most appropriate classification scheme of the worker seems to be by the combination of factory and job category.

Polycyclic aromatic hydrocarbon exposure in coal liquefaction workers: The value of urinary 1-hydroxypyrene excretion in the development of occupational hygiene control strategies

Studies in coal liquefaction workers were conducted to examine relationships between work activities, exposure to polycyclic aromatic hydrocarbons (PAHs) and excretion of urinary 1-hydroxypyrene (1-OHP). In a single-week study in operators, the end of work period 1-OHP excretion was an order of magnitude higher than in a shadow control subject, who experienced exposure by inhalation only (shadowed operator = 15.8 mumol mol-1 creatinine; shadow control = 1.07 mumol mol-1 creatinine). Dermal exposure was estimated to account for over 70% of excreted 1-OHP in exposed workers. A second study over 4 consecutive weeks (multi-week study) showed consistency in 1-OHP excretion from week to week both in operators and laboratory technicians, indicating little variation in weekly exposures for these workers. Excretion levels in maintenance workers however, showed some week to week variation, consistent with the variable nature of exposures associated with this type of work. A further study involving an end of work period spot assessment for all personnel showed a clear distinction between exposed workers (operators and maintenance staff) and other workers not thought to be exposed (laboratory technicians and office staff). Findings in the course of these studies indicated that there is no loss of 1-OHP at 4 degrees C, compared with -20 degrees C. On the basis of work to date at the coal liquefaction facility, hygiene control strategies have been proposed involving periodic urinary 1-OHP monitoring.

Occupational exposure to carbon black in its manufacture: Data from 1987 to 1992

Carbon black is a very pure form of very finely divided particulate carbon used mainly in the automotive tyre industry. Its carbonaceous nature and submicron size (unpelleted) have raised concerns with regard to its ability to affect respiratory morbidity. This paper describes the exposure to carbon black dust in the first and second phase of a large multi-national epidemiological study investigating the magnitude of these exposure-related effects. In Phase I, 1278 respirable dust samples were taken (SIMPEDS cyclone) which increased to 2941 in Phase II with a similar rise in the number of total inhalable dust samples (IOM head) from 1288 in Phase I to 3433 Phase II. Exposure dropped markedly between the two phases with total inhalable dust showing a bigger reduction (49.9%) than respirable dust (42%), although the mean exposure for certain factories and job categories dropped more than others. The data are presented by the 14 job titles/numbers (21-34). The highest mean exposure in both phases and for both dust fractions is experienced by the warehouse packers and they are also most likely to exceed the OES of 3.5 mg m-3 (35.1% of samples in Phase I and 12.0% in Phase II).

Investigation of dose related neurobehavioural effects in paintmakers exposed to low levels of solvents.

A cross sectional study was carried out to compare 110 paintmakers exposed to solvents with 110 age matched controls for outcome measures designed to assess cognitive performance and mental health. Hygiene data available for the paintmakers allowed the development of individual indices of solvent exposure and the analyses of health effects in relation to both duration and intensity of exposure. No effects on cognitive functioning or mental health were found in the paintmakers. For most of their period of employment the exposure of the paintmakers had been below current occupational exposure limits. The results are therefore interpreted as providing support for the view that long term exposure at or below current compliance levels does not result in damage to the central nervous system.

Assessment of the sensitivity of the relation between current exposure to carbon black and lung function parameters when using different grouping schemes.

BACKGROUND Equations using variance components in exposure data to predict attenuation and standard error of exposure--response slopes have been published recently. However, to date, no comparisons have been made between results of applying these equations to a real data set with the exposure-response relations estimated directly. METHODS Data on lung function parameters and personal inhalable and respirable dust exposure levels from the European carbon black respiratory health study were used. The predicted attenuation and standard error of the relation between current inhalable and respirable dust levels and lung function parameters (FVC and FEV(1)) were calculated for various exposure grouping schemes. These results were compared with the observed exposure-response relations. Workers were grouped by Job Category, the combination of factory and Job Category and five a posteriori created Exposure Groups. In addition, the individual approach was also used, as exposure data were available for each worker. RESULTS The rank orders of the coefficients from the regression analyses using the different grouping schemes were similar to those predicted by the equations, although the differences were larger than predicted. When using inhalable dust exposure, the predicted standard errors of the exposure-response slopes were slightly lower than those estimated directly; for respirable dust the predicted standard errors were about a factor two to three smaller than those from the regression analyses. When considering FVC, the predicted exposure-response relations were all statistically significant, whilst the observed relation was only significant when using the five a posteriori Exposure Groups. When reviewing the relations between dust exposure and level of FEV(1), all relations were statistically significant, with the exception of the (observed) relation between respirable dust and FEV(1), when the individual approach was used. CONCLUSIONS Using different grouping schemes for estimating exposure can have large effects on the slope and standard error of the exposure-response relation. It is, therefore, important that the effect of the different grouping schemes on the level and precision of the exposure-response slope be estimated. Despite violation of most of the assumptions when applying the equations to predict attenuation and the standard error of the exposure-response slope, the similarities in predicted and observed exposure-response relations and standard errors are indicative of the robustness of these equations. Therefore, the equations appear to be a useful tool in establishing the most efficient way of utilizing exposure measurements.

Are the respiratory health effects found in manufacturers of ceramic fibres due to the dust rather than the exposure to fibres

OBJECTIVES--To determine whether the respiratory symptoms and decrements in lung function found in manufacturers of ceramic fibres are related to exposure to the respirable fibre or inspirable mass constituents of the air in the working environment. METHODS--Cross sectional survey of all current European primary producers of ceramic fibre was carried out, with measurement of exposure to respiratory fibres by personal samplers that measured inspirable and total mass, together with a health survey with an expanded respiratory questionnaire and standardised measurement of lung function. Odds ratios were calculated for symptoms and current exposure by multiple logistic regression, and multiple linear regression coefficients for lung function related to cumulative exposures controlled for the effects of respirable fibre and inspirable mass separately and together. RESULTS--Significant effects of current exposure to both inspirable dust and respirable fibres were related to dry cough, stuffy nose, eye and skin irritation and breathlessness. The decrements found in smokers and to some extent in ex-smokers in forced expiratory volume in one second and forced expiratory flow from 25% to 75% of expiratory volume, seem to be related to the respirable fibres rather than the inspirable mass constituents of the environment. CONCLUSIONS--Current symptoms were related to both current exposure to inspirable dust and respirable fibre. The decrements in lung function were related to the fibre constituent of the exposure.

The PlayMate System

Research in CoSy was scenario driven. Two scenarios were created, the Play- Mate and the Explorer. One of the integration goals of the project was to build integrated systems that addressed the tasks in these two scenarios. This chapter concerns the integrated system for the PlayMate scenario.