Biomedical subjects

H Kromhout

Publications and source records attributed to H Kromhout.

At least 91 records · Page 5Linked to original sources

PubMed1996

Experts' subjective assessment of pesticide exposure in fruit growing.

OBJECTIVES: Exposure to pesticides in fruit growing was estimated by pesticide experts, occupational hygienists, and fruit growing experts to determine whether valid subjective assessments can be made by experts. The study objectives were (i) validation of exposure assessment by experts using different sources of information, (ii) assessment of interrater agreement, (iii) measurement of agreement between experts' assessments and actual quantitative exposure data. METHODS: Three groups with different expertise made four ratings. Three of the ratings were made in three phases in which exposure information was provided. RESULTS: The intraclass correlation was high for each subgroup of experts when tasks in fruit growing were relatively ranked by increasing exposure level. In general, the interrater agreement on factors influencing the internal dose decreased when more information on exposure was provided. Experts correctly considered dermal exposure as the prominent contributor to internal dose. Results were comparable for the three pesticides under study. The ranking of 15 specific sprayings with a fungicide clearly showed differences between raters according to their expertise. The pesticide experts and occupational hygienists were able to rank daily exposure levels during pesticide spraying in a meaningful way. CONCLUSIONS: Experts seem to recognize the most important determinants of external exposure and therefore should be able pay a role in evaluating the effectiveness of control measures taken to reduce external exposure and to determine exposure groups in epidemiologic studies. The expert panel should not be too small, and consensus or average estimates should be used because differences within expert groups can be considerable.

Agriculture↗

PubMed1995

Occupational epidemiology in the rubber industry: implications of exposure variability.

The variability of exposure has important implications for the design of occupational epidemiologic studies. To assess the influence of this variability in the rubber industry, the efficiency of different schemes for classification of exposure to particulates, cyclohexane-soluble contaminants, and solvents was assessed. Groupings based on job title, plant, factors affecting exposure, published classifications, and the International Standard Classification of Occupations of the International Labor Organization (ISCO-ILO) were compared. Statistical parameters for contrast in average exposure between groups and precision of average exposure within groups were developed to enable comparison of the efficiency of different classification schemes. Grouping of exposure to particulates and dermal exposure appeared to be less efficient than grouping of exposure to solvents. Grouping of solvent exposure using occupational title groups, existing classification schemes, and schemes based on factors affecting exposure showed comparable high resolution in exposure levels. Even the most detailed grouping schemes based on the combination of plant and occupational title group showed relatively modest resolution in particulate and dermal exposure levels. Groupings based on factors affecting exposure showed similar resolution for these exposures, but had higher precision due to having fewer groups. Application of optimal exposure grouping strategies will benefit new research on cancer among rubber workers. Eventually, this might resolve the situation in which a complete industry was included on the list of proven human carcinogens.

Analysis of Variance↗

PubMed1995

Urinary excretion of tetrahydrophtalimide in fruit growers with dermal exposure to captan.

The relation between dermal and respiratory exposure and uptake into the body of captan, measured as 24 hr cumulative tetrahydrophtalimide (THPI) dose, was studied among 14 male fruit growers applying pesticides in orchards in the Netherlands. No contribution of respiratory exposure was observed on THPI in the urine. Dermal exposure, measured with skin pads, showed a clear relation with THPI in urine when exposure was estimated from exposure on skin pads of ankles and neck. No relation was found for total dermal exposure, calculated from measured exposure on skin pads of representative skin areas according to models described in the literature. Determinants of exposure such as use of a cabin on the tractor, use of gloves during mixing and loading, and use of rubber boots also explained THPI in urine very well. This finding corroborated the findings on measured dermal exposure. Results indicate that more attention should be paid to skin areas which are suspected to be most permeable for a chemical under study. It was concluded that dermal exposure data can be linked better to biological monitoring based on empirical findings as gathered in a pilot study on exposure of specific body areas than on estimations of total skin dose.

Adult↗

PubMed1995

Cancer risk for European asphalt workers.

OBJECTIVES: The feasibility of a European epidemiologic study of cancer risk among asphalt workers was examined in Western Europe. The study was motivated by occupational and public health concern about possible health risk from exposure to bitumen fumes. METHODS: Information on the accessibility and quality of epidemiologic resources, retrospective worker records, mortality and cancer incidence records, and exposures was requested from research institutes and road paving and asphalt mixing companies in 15 European countries. RESULTS: Research institutes and asphalt companies in 12 countries responded. It was found that at least 44 companies in seven countries can be included in a retrospective mortality study of a minimum of 32,000 employees with 356,000 person-years (over 100 lung cancers). Coal tar will be an important confounder for these data. The power of a cohort study of workers who have never worked with tar-containing materials remains insufficient. Even in an ambispective study extending to the year 2005, the expected lung cancer deaths in a tar-free cohort would be only four. CONCLUSIONS: The results suggest that a case-referent study of lung cancer, nested in an international cohort of asphalt workers, represents the design of choice, conditionally on the possibility of assessing relevant individual life-time exposures. A cross-sectional determination of relevant biomarkers of exposure such as adducts in lymphocytes or the presence of metabolites of polycyclic aromatic compounds in urine in a group of workers exposed to bitumen fumes will provide further relevant information.

Adult↗

PubMed1995

Modeling long-term average exposure in occupational exposure-response analysis.

OBJECTIVES: Estimates of long-term average exposure to occupational hazards are often imprecise because intraindividual variability in exposure can be large and exposure is usually based on one or few measurements. One potential result is bias of exposure-response relationships. The possibility was studied of a more valid measure of exposure being obtained by modeling exposure and consequently increasing the number of days with exposure estimates, using simple measurable exposure surrogates. METHODS: In a group of 198 Dutch pig farmers, exposure to endotoxins was measured on one workday in summer and one day in winter. Farmers recorded activity patterns during one week in both seasons, and farm characteristics were evaluated. Relationships between farm characteristics and activities and log-transformed measured exposure levels were quantified in a multiple regression analysis. Exposure was estimated for 14 d with known activity patterns. RESULTS: The ratio of intraindividual and interindividual variance in log-transformed measured exposure was 4.7. Given this ratio, the true regression coefficient of lung function on exposure would potentially be attenuated by 70%. The variance ratio for predicted exposures was only 1.2, and the potential attenuation by variation in exposure estimates was decreased to 8%. There was no relationship between lung function and measured exposure. Modeled long-term average exposure was inversely related to base-line lung function; it reached statistical significance for asymptomatic farmers. CONCLUSIONS: The results suggest that the presented strategy offers a possibility to minimize measurement effort in occupational epidemiologic studies, without apparent loss of statistical power.

Adult↗

PubMed1995

Assessment and grouping of occupational magnetic field exposure in five electric utility companies.

OBJECTIVES: Occupational exposure to 60-Hz magnetic fields was surveyed among randomly selected workers in five electric power companies. METHODS: The study facilitated the examination of exposure variability and provided the base for a job-exposure matrix linking health outcomes and occupational magnetic field exposures. RESULTS: Average exposures ranged from 0.11 to 1.50 microT. The differences among the five companies were small, the more urban companies showing somewhat higher averages. The day-to-day component of variance exceeded the within- and between-group components of variance. The final job-exposure matrix consisted of five groups with average exposure levels of 0.12, 0.21, 0.39, 0.62, and 1.27 microT. Given the variance in exposure, even this optimal grouping considerably overlapped. CONCLUSIONS: The job-exposure matrix used in this study efficiently incorporated the differences in exposure within occupational categories between companies and provided an objective and statistically based method for estimating cumulative magnetic field exposure.

Adult↗

PubMed1995

Wood-dust exposure during wood-working processes.

Personal and ambient full shift concentrations of inhalable wood dust were measured at different wood-working processes in two joineries and a furniture factory in The Netherlands. The current occupational exposure limit for wood dust is still 5 mg m-3 total dust, but the Dutch Expert Committee for Occupational Standards has recently recommended a health-based limit of 0.2 mg m-3 (total wood dust). The main purpose of the present study was to characterize current wood-dust exposures during different wood-working activities in order to determine whether compliance with the proposed limit was feasible. The wood-dust exposures in the joineries were usually much lower than 5 mg m-3, but in the furniture factory the present limit was regularly exceeded. Sanding, especially hand sanding, nearly always resulted in exposures above 5 mg m-3. Almost all personal exposures were higher than the proposed health-based limit of 0.2 mg m-3 and therefore can be considered to generate a health risk to the workers. The measurements performed may help in setting priorities and will serve as a basis for the development of a control strategy to reduce the average exposure.

Dust↗

PubMed1995

Determinants of dust and endotoxin exposure of pig farmers: development of a control strategy using empirical modelling.

Personal exposure to dust and endotoxin was measured among 198 Dutch pig farmers. For each participant 8-h measurements were made on 2 days, one in summer 1991 and one in winter 1992. Mean time-weighted average (TWA) exposure to dust was 3.0 mg m-3 (arithmetic mean, range 0.3-27 mg m-3) and mean TWA exposure to endotoxin was 130 ng m-3 (arithmetic mean, range 6-1503 mg m-3). Empirical statistical modelling was applied to identify activities and farm characteristics associated with exposure. In a multiple least-squares regression analysis, aspects of hygiene and feeding were major characteristics associated with dust exposure. Flooring and feeding were predominant characteristics explaining variation in endotoxin exposure. Activities performed frequently, like feeding and controlling, cleaning activities and activities in which very active animals were involved, such as teeth cutting and ear tagging, were associated with exposure to dust and endotoxin. The models were used to set priorities for the development of control measures to eliminate the dust and endotoxin hazard of pig farmers.

Animal Husbandry↗

PubMed1994

Organization and classification of work history data in industry-wide studies: an application to the electric power industry.

Industry-based cohort studies require systems for organizing work history data. Although the ultimate goal may be to assess the hazards of specific exposures, classification of the job titles that comprise work histories serves an important descriptive purpose in itself and is often necessary before exposure data can be obtained. A system we have created for organizing jobs in a study of 135,000 workers at five electric power companies highlights conceptual and practical issues in managing work history data for epidemiological studies. Job characteristics including function, location, and authority were used to develop a system of 28 occupational categories. Comprehensibility, flexibility, and efficiency were important criteria in designing the system. Assessment of exposures was an implicit goal; the same categories will define job-exposure matrices for numerous agents. A combination of computer algorithms and expert judgment was used to assign individual job titles to the categories. This system facilitates examining the effects of various agents and controlling for confounding. The 28 categories can be collapsed and regrouped to analyze disease risks in relation to exposures to magnetic fields and other agents; even exposures not previously considered could be brought into the study with this generic system for organizing the electric power industry.

Data Collection↗

PubMed1994

Empirical modelling of chemical exposure in the rubber-manufacturing industry.

As part of a study of working conditions chemical exposure was assessed in 10 rubber-manufacturing plants in The Netherlands. Personal exposures to airborne particulates, rubber fumes and solvents, and also dermal contamination, were measured. To identify factors affecting exposure the personal exposure levels and information on tasks performed, ventilation characteristics and production variables were used in multiple linear regression models. The exposure was generally very variable. The specific circumstances in each department of each plant determined the actual levels of exposure to a large extent. The factors affecting exposure turned out to be different for each of the types of exposure considered. The model for exposure to airborne particulates explained 40% of the total variability and incorporating the actual time spent on a task only slightly improved the model (R2 = 0.42). The handling of chemicals in powder form was the main factor affecting exposure, forced ventilation having a negligible effect. The model for exposure to curing fumes (measured as the cyclohexane-soluble fraction of the particulate matter) explained 50% of the variability. Both curing temperature and pressure determined the level of rubber fumes. Local exhaust ventilation showed a significant exposure reducing effect. The effect of curing different elastomers was not statistically significant. Dermal exposure to cyclohexane-soluble matter could only be explained to a limited extent (R2 = 0.22). Tasks with frequent contact with (warm) compound and maintenance tasks in the engineering services departments resulted in high dermal exposure. Tasks in which solvents were directly used explained 56% of the variation in solvent exposures. Exposure data, together with information on tasks, methods of work, ventilation and production throughout a branch of industry, can be used to derive empirical statistical models which occupational hygienists can apply to study factors affecting exposure. These determining factors are of crucial importance, whenever hazard control or epidemiological research is the ultimate goal.

Air Pollutants, Occupational↗

PubMed1994

Occupational exposures estimated by a population specific job exposure matrix and 25 year incidence rate of chronic nonspecific lung disease (CNSLD): the Zutphen Study.

The influence of occupational exposures on total mortality and respiratory mortality and morbidity was examined, employing a population specific Job Exposure Matrix (JEM). Moreover, the relationship between time-related variables of exposure to dust and chronic nonspecific lung disease (CNSLD) incidence was analysed, using time since first exposure and duration of exposure. Occupational exposures in the Zutphen cohort were assessed by application of a JEM, arbitrarily considering jobs as exposed when at least 10% of men who had held the job of interest reported an exposure to one or more from a list of 27 chemical agents. None of the exposures was related to mortality due to CNSLD, although results were influenced by the healthy-worker effect and low mortality rates. Exposure to wood dust and a high probability of exposure to dust were associated with total mortality. Exposures to dust and solvents were statistically significantly related to CNSLD incidence. An exposure-response relationship was found for the probability of exposure to dust with CNSLD incidence. Time-related estimates of exposure to dust based on work history were negatively related to CNSLD incidence. The results suggest the presence of a healthy-worker effect, in a general population study, resulting in an underestimation of the relationship between occupational exposures and respiratory diseases based on the evidence published so far. The use of the full work history to determine exposure to dust leads to stronger relationships with CNSLD incidence, compared to conventional analyses using exposure at the start of follow-up.

Age Factors↗

PubMed1993

The relationship between polycyclic aromatic hydrocarbons in air and in urine of workers in a Söderberg potroom.

The relationships between increase of urinary 1-hydroxypyrene over the workweek and the airborne concentrations of benzo(a)pyrene and coal tar pitch volatiles (CTPVs) were studied among groups of workers in a vertical-stud Söderberg potroom of an aluminum smelter. There was a strong correlation between the natural logarithm of the pyrene concentration and the natural logarithm of the total polycyclic aromatic hydrocarbon (PAHs) concentration in personal air samples (r = 0.94). 1-Hydroxypyrene as the major metabolite of pyrene, a polycyclic aromatic hydrocarbon, was used as a marker for exposure to PAHs. A strong positive correlation was found between the natural logarithm of increase of urinary 1-hydroxypyrene and the natural logarithm of the estimated airborne PAH exposure (R2 = 0.84 with CTPV) when the use of facial protective clothing was taken into account. The relationship between increase of urinary 1-hydroxypyrene and PAHs differed for workers who used facial protective clothing under their respirators compared to those who did not. A contradictory fact was found: the use of facial protection seemed to lead to an elevated increase of 1-hydroxypyrene over the workweek. The regression model for the relationship between increase of urinary 1-hydroxypyrene over the workweek and airborne CTPV was: LN(change in 1-hydroxypyrene) = -4.7 + 1.2 LN(CTPV) -0.44 LN(CTPV)*(use of facial protection) + 3.5 (use of facial protection).

Air Pollutants, Occupational↗

PubMed1993

Variation of exposure between workers in homogeneous exposure groups.

It is generally assumed that workers employed in the same job at a given location are uniformly exposed, i.e., that they have the same long-term mean exposure. This assumption has led to observational schemes for classifying workers into homogeneous exposure groups (HEGs), based on job title, location, and other identifiable features of the work environment. This paper presents results from analysis of 183 HEGs (comprised of 15,495 personal measurements) in which it was possible to determine the between-worker component of variance in exposure. The results indicate that, contrary to popular belief, only about one fifth of the HEGs were uniformly exposed (less than a two-fold difference among 95% of individual mean exposures) while an equal number showed a high degree of variation between workers (more than 15-fold differences among 95% of individuals). Further analyses indicate that the identifiable features of the work environment, which are typically used to establish HEGs, are only marginally related to the between-person variation (accounting for only 13% of this variance component). It is concluded that industrial hygienists should not rely on observational schemes to guarantee that groups of workers are uniformly exposed. Rather, they should adopt methods of statistical sampling and analysis that allow the variance components to be estimated so that decisions regarding the evaluation of hazard and selection of controls will be appropriate.

Analysis of Variance↗

PubMed1993

Prevention and control of chemical exposures in the rubber manufacturing industry in The Netherlands.

In a survey in the rubber manufacturing industry in The Netherlands both the chemical and physical exposure of operators as well as company policies on working conditions were assessed. Defining the effectiveness of control measures was a part of this study and is the subject of this article. A method of solution-directed workplace analysis was applied to compare and evaluate the control measures within this branch of industry. Elimination of sources appears to be a strategy for prevention which has been adopted on only a limited scale. Control of exposure to particulates is more frequently applied, with local exhaust ventilation as the most important control measure. Both qualitative and quantitative analysis confirmed that local exhaust ventilation has a limited effect. Dust-free forms of chemicals, especially those with health risks, are used on only a moderate scale. In addition to hazard identification and evaluation based on exposure levels, the foreseeable risks associated with the design and requirements of production processes were established. The forthcoming industrial agreement for the rubber manufacturing industry in The Netherlands will, amongst other measures, stimulate use of source related strategies.

Environmental Monitoring↗

PubMed1993

A comprehensive evaluation of within- and between-worker components of occupational exposure to chemical agents.

A database of approximately 20,000 chemical exposures has been constructed in close co-operation between the School of Public Health of the University of North Carolina at Chapel Hill and the Department of Air Pollution of the Wageningen Agricultural University. A special feature of this database is that only multiple measurements of exposure from the same workers were included. This enabled estimation of within- and between-worker variance components of occupational exposure to chemical agents throughout industry. Most of the groups were not uniformly exposed as is generally assumed by occupational hygienists. In fact only 42 out of a total of 165 groups (25%), based on job title and factory, had 95% of individual mean exposures within a two-fold range. On the contrary, about 30% of the groups had 95% of individual mean exposures in a range which was greater than 10-fold. Environmental and production factors were shown to have distinct influences on the within-worker (day-to-day) variability, but not on the between-worker variability. Groups working outdoors and those working without local exhaust ventilation showed more day-to-day variability than groups working indoors and those working with local exhaust ventilation. Groups consisting of mobile workers, those working with an intermittent process and those where the source of contamination was either local or mobile also showed great day-to-day variability. In a multivariate regression model, environment (indoors-outdoors) and type of process (continuous-intermittent) explained 41% of the variability in the within-worker component of variance. Another model, in which only type of process (continuous-intermittent) had a significant effect, explained only 13% of the variability in the between-worker component of variance.

Air Pollutants, Occupational↗

PubMed1993

Job exposure matrices in industry.

Job exposure matrices (JEM) are designed to link information on occupation with information on exposure to specific workplace hazards. In spite of some limitations, JEM are particularly useful in large retrospective epidemiological studies. The development of JEM designed for a company or an industrial sector have a more specific field of application than JEM used in population-based studies, and can therefore be based on a more detailed classification of occupations and better exposure information. This article reviews on-going research related to the design of JEM in support of industry-based studies. The review covers design aspects related to the structure of JEM, and specially the four main axes that may produce differences on exposure characteristics: agent (exposure), job, time and place. Attention has also been given to the different sources of information on exposure, the characteristics of the exposure and the validation of exposure estimates.

Data Collection↗

PubMed1992

Performance of two general job-exposure matrices in a study of lung cancer morbidity in the Zutphen cohort.

Data from a general population cohort of 878 men from the town of Zutphen, The Netherlands, were used to evaluate the performance of two general job-exposure matrices. Exposures generated by the job-exposure matrices on the basis of job histories were compared. The validity of those exposures was measured against exposures reported by the participants in 1977/1978. The performance of the different exposure measures was assessed in proportional hazards analyses of lung cancer morbidity incidence. The two general job-exposure matrices generally disagreed with regard to exposure classification because of differences in exposure assessment and level of detail of the job axis. When compared with self-reported exposures, the sensitivity of both job-exposure matrices was low (on average, below 0.51), while the specificity was generally high (on average, above 0.90). Self-reported exposures to asbestos, pesticides, and welding fumes showed elevated risk ratios for lung cancer which were absent for exposures generated by the two job-exposure matrices. Thus, a population-specific job-exposure matrix is proposed as an alternative to general job-exposure matrices developed elsewhere. Such a matrix can be constructed from the results of in-depth interviews of a job-stratified sample of cohort members. Sound validation and documentation of exposure assessment methods used in job-exposure matrices are recommended.

Adult↗

PubMed1992

Relations between occupation, smoking, lung function, and incidence and mortality of chronic non-specific lung disease: the Zutphen Study.

Information gathered in the "Zutphen study", the Dutch contribution to the Seven Countries Study was used for the present study. Follow up data from 1965 to 1 July 1985 were used. During this follow up, the morbidity state of the participants was verified at regular intervals. In 1965 lung function was measured by spirometry and the vital capacity (VC) and forced expiratory volume in one second (FEV1) were available. A complete set of data was available for 668 men. The occurrence of chronic non-specific lung disease (CNSLD) at a specific time was coded by one physician, using strict criteria. Information about the cause of death was obtained and coded by one physician in 1985. Occupation was coded and a distinction between blue and white collar workers was made. For the analysis of the relation between age, lung function, smoking habits, and occupational state with CNSLD incidence and mortality, proportional hazard models were used. Blue collar workers had a significantly raised risk for incidence of CNSLD only. The hazard ratio for blue v white collar workers with CNSLD mortality was 1.4 but not statistically significant. It was concluded that occupation is clearly related to incidence of CNSLD. There were indications that occupation is related to mortality from CNSLD. A reduced FEV1 was a strong predictor of both CNSLD incidence and mortality. It is noteworthy that small differences in age and height standardised lung function were significantly related to incidence of CNSLD, mortality from CNSLD, and total mortality. Although these differences in lung function have no direct clinical importance for the individual subject, they indicate a raised morbidity and mortality risk for the population.

Age Factors↗