Biomedical subjects

L L Kupper

Publications and source records attributed to L L Kupper.

At least 19 recordsLinked to original sources

PubMed2006

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.

Adolescent↗

PubMed2005

Air samples versus biomarkers for epidemiology.

BACKGROUND: It has been speculated on theoretical grounds that biomarkers are superior surrogates for chemical exposures to air samples in epidemiology studies. METHODS AND RESULTS: Biomarkers were classified according to their position in the exposure-disease continuum-that is, parent compound, reactive intermediate, stable metabolite, macromolecular adduct, or measure of cellular damage. Because airborne exposures and these different biomarkers are time series that vary within and between persons in a population, they are all prone to measurement error effects when used as surrogates for true chemical exposures. It was shown that the attenuation bias in the estimated slope characterising a log exposure-log disease relation should decrease as the within- to between-person variance ratio of a given set of air or biomarker measurements decreases. To gauge the magnitudes of these variance ratios, a database of 12,077 repeated observations was constructed from 127 datasets, including air and biological measurements from either occupational or environmental settings. The within- and between-person variance components (in log scale, after controlling for fixed effects of time) and the corresponding variance ratios for each set of air and biomarker measurements were estimated. It was shown that estimated variance ratios of biomarkers decreased in the order short term (residence time < or =2 days) > intermediate term (2 days < residence time < or =2 months) > long term biomarkers (residence time >2 months). Overall, biomarkers had smaller variance ratios than air measurements, particularly in environmental settings. This suggests that a typical biomarker would provide a less biasing surrogate for exposure than would a typical air measurement. CONCLUSION: Epidemiologists are encouraged to consider the magnitudes of variance ratios, along with other factors related to practicality and cost, in choosing among candidate surrogate measures of exposure.

Air Pollutants↗

PubMed2004

On the importance of exposure variability to the doses of volatile organic compounds.

The connection between occupational exposure to volatile organic compounds (VOCs) and the resulting internal doses is complicated by variability in air levels from day to day and by nonlinear kinetics of metabolism. We investigated long-term liver doses of VOCs and their metabolites using a physiologically based toxicokinetic model, to which 10,000 random 8-h exposures were inputted. Three carcinogenic VOCs were studied (i.e., benzene, perchloroethylene, and acrylonitrile); these compounds are all bioactivated in the liver and represent a wide range of an important toxicokinetic parameter Vmax/QL x KM. For each VOC, simulations were performed using mean air concentrations (muX) between 0.0003 and 1 mg/l (which covers both linear and saturated metabolism) and using coefficients of variation of exposure (CVX) between 0.23 and 2.18 (which includes most occupational settings). Two long-term measures of internal dose were examined, i.e., the area under the liver concentration-time curve (AUCL) and the area under the metabolic rate-time curve (AURC). Interestingly, both AUCL and AURC were linear functions of cumulative exposure (CE, mg x h/l air) even when metabolism was saturated and CVX was large. Yet, at a given CE, both AUCL and AURC were affected by CVX, with the magnitude of the effect increasing with Vmax/QL x KM (i.e., perchloroethylene < benzene < acrylonitrile). Nonetheless, the effects of CVX were typically only a few percent and should be of little consequence unless a VOC has large values of Vmax/QL x KM, muX,and CVX. We conclude that CE should be a sufficient predictor of the dose of either the parent chemical (VOC) or its metabolite in the liver, even when metabolism is nonlinear. We also observed that AUCL and AURC were sensitive to changes in values of model parameters in the high-variability scenarios, suggesting that (when CVX is large) the population variability of AUCL and AURC can be quite large at a fixed CE.

Acrylonitrile↗

PubMed2001

Physical abuse of women before, during, and after pregnancy.

CONTEXT: Clinicians who care for new mothers and infants need information concerning postpartum physical abuse of women as a foundation on which to develop appropriate clinical screening and intervention procedures. However, no previous population-based studies have been conducted of postpartum physical abuse. OBJECTIVES: To examine patterns of physical abuse before, during, and after pregnancy in a representative statewide sample of North Carolina women. DESIGN, SETTING, AND PARTICIPANTS: Survey of participants in the North Carolina Pregnancy Risk Assessment Monitoring System (NC PRAMS). Of the 3542 women invited to participate in NC PRAMS between July 1, 1997, and December 31, 1998, 75% (n = 2648) responded. MAIN OUTCOME MEASURES: Prevalence of physical abuse during the 12 months before pregnancy, during pregnancy, and after infant delivery; injuries and medical interventions resulting from postpartum abuse; and patterns of abuse over time in relation to sociodemographic characteristics and use of well-baby care. RESULTS: The prevalence of abuse before pregnancy was 6.9% (95% confidence interval [CI], 5.6%-8.2%) compared with 6.1% (95% CI, 4.8%-7.4%) during pregnancy and 3.2% (95% CI, 2.3%-4.1%) during a mean postpartum period of 3.6 months. Abuse during a previous period was strongly predictive of later abuse. Most women who were abused after pregnancy (77%) were injured, but only 23% received medical treatment for their injuries. Virtually all abused and nonabused women used well-baby care; private physicians were the most common source of care. The mean number of well-baby care visits did not differ significantly by maternal patterns of abuse. CONCLUSION: Since well-baby care use is similar for abused and nonabused mothers, pediatric practices may be important settings for screening women for violence.

Adolescent↗

PubMed2001

Preventive counseling during prenatal care: Pregnancy Risk Assessment Monitoring System (PRAMS).

BACKGROUND: Prenatal care provides an opportunity for counseling about behaviors and experiences that increase the likelihood of adverse maternal and fetal outcomes. OBJECTIVE: To document (1) prevalence of preventive health counseling during prenatal care, (2) prevalence of women in higher need of counseling about specific health concerns, and (3) whether women in higher need for counseling were more likely than women in lower need to have received counseling. METHODS: Analysis of the Pregnancy Risk Assessment Monitoring System (PRAMS), a state-specific, population-based, random sample of postpartum women, was performed by using data from 14 states for births during 1997 or 1998, for a total of 24,620 participants. Outcome measures included report of preventive health counseling during prenatal visits by specific topic as well as behaviors and experiences about cigarette use, alcohol use, breast-feeding, partner violence, and preterm labor. RESULTS: The percentage of women that report preventive counseling during prenatal care is relatively high (> or =75%) for 9 of 13 topics. However, the percentage of women that report counseling is relatively low (<75%) for partner violence, seat belt use, illegal drug use, and human immunodeficiency virus (HIV) risk. Except for counseling about cigarette and alcohol use, women in higher need, compared with women in lower need, for three other health topics were not significantly more likely to receive counseling. CONCLUSIONS: Preventive health counseling for partner violence, seat-belt use, illegal drug use, and risk of HIV could be increased across prenatal settings. Counseling should involve assessment of risks, with focused counseling related to those risks.

Adolescent↗

PubMed2001

Stressful life events and physical abuse among pregnant women in North Carolina.

OBJECTIVES: This study estimates the prevalence of stressful life events and physical abuse among North Carolina women prior to infant delivery, and examines potential associations between abuse and the other stressors. METHODS: Data were from the North Carolina Pregnancy Risk Assessment Monitoring System, a statewide representative survey of over 2,600 postpartum women. The survey assessed women's sociodemographic characteristics and their experiences of physical abuse and 13 other stressful life events before delivery. The prevalences of each life event and abuse were estimated. Logistic regression modeled the probability of women having high levels of stressful life events in relation to physical abuse and sociodemographics. RESULTS: Most women were married, white, high school graduates, aged 20 or older. The most common stressful life events were residential moves, increased arguing with husbands/partners, family member hospitalizations, financial hardship, and deaths of loved ones. Fourteen percent of women had high levels of stressful events (5 or more), and almost 9% were physically abused. Abuse was positively associated with increased arguing with husbands/partners, physical fighting, having someone close with an alcohol/drug problem, becoming separated/divorced, and financial hardship. Logistic regression analysis showed that a high level of stressful life events was significantly more likely among women abused both before and during pregnancy (OR = 11.94) and among women abused before but not during pregnancy (OR = 14.19). CONCLUSIONS: The high frequency of multiple stressful events and abuse in women's lives suggests that women's care providers should ask their patients about these issues, and offer appropriate referral/interventions to those in need.

Adolescent↗

PubMed2001

A mixture model for occupational exposure mean testing with a limit of detection.

Information from detectable exposure measurements randomly sampled from a left-truncated log-normal distribution may be used to evaluate the distribution of nondetectable values that fall below an analytic limit of detection. If the proportion of nondetects is larger than expected under log normality, alternative models to account for these unobserved data should be considered. We discuss one such model that incorporates a mixture of true zero exposures and a log-normal distribution with possible left censoring, previously considered in a different context by Moulton and Halsey (1995, Biometrics 51, 1570-1578). A particular relationship is demonstrated between maximum likelihood parameter estimates based on this mixture model and those assuming either left-truncated or left-censored data. These results emphasize the need for caution when choosing a model to fit data involving nondetectable values. A one-sided likelihood ratio test for comparing mean exposure under the mixture model to an occupational exposure limit is then developed and evaluated via simulations. An example demonstrates the potential impact of specifying an incorrect model for the nondetectable values.

Algorithms↗

PubMed2001

Partner violence among adolescents in opposite-sex romantic relationships: findings from the National Longitudinal Study of Adolescent Health.

OBJECTIVES: This report examines (1) the prevalence of psychological and minor physical violence victimization in a nationally representative sample of adolescents and (2) associations between sociodemographic factors and victimization. METHODS: Analyses are based on 7500 adolescents who reported exclusively heterosexual romantic relationships in the National Longitudinal Study of Adolescent Health. Items from the Conflict Tactics Scale were used to measure victimization. Associations between victimization patterns and sociodemographic characteristics were assessed with polytomous logistic regression. RESULTS: One third of adolescents reported some type of victimization, and 12% reported physical violence victimization. Although most sociodemographic characteristics were significantly associated with victimization, patterns varied by sex and type of victimization. CONCLUSIONS: Psychological and minor physical violence victimization is common in opposite-sex romantic relationships during adolescence. The sex-specific associations between sociodemographic characteristics and patterns of partner violence victimization underscore the importance of pursuing longitudinal, theory-driven investigations of the characteristics and developmental histories of both partners in a couple to advance understanding of this public health problem.

Adolescent↗

PubMed2001

Simultaneous assessment of occupational exposures from multiple worker groups.

The methods developed by Rappaport et al. [Ann. Occup. Hyg. 39 (1995) 469] and Lyles et al. [J. Agri. Bio. Environ. Stat. 2 (1997a) 64; Ann. Occup. Hyg. 41 (1997b) 63]) for assessing workplace exposures on a group-by-group basis are extended to allow for the simultaneous assessment of data from multiple worker groups within the same industry. These extended methods allow models to be fit simultaneously to data on all groups in a study, even when some of the groups might not contribute adequate information to be modeled separately. We assume that the exposures are log-normally distributed, and that they can be adequately modeled by a mixed effects regression model with parameters for exposure levels and for between- and within-worker variance components. Simultaneously analyzing data from multiple groups is only advantageous when at least one of these variance components can be assumed to be homogeneous across the groups. Here, we advocate testing an assumption of homogeneous within-worker variance components, sigma(2)(w,h), using a likelihood ratio test to choose between a full model (distinct sigma(2)(w,h) for each group) and a reduced model (common sigma(2)(w) across groups). We then develop a procedure, which is conditional on the results of the likelihood ratio test, for testing whether or not each group of workers is overexposed to the contaminant of interest. This modeling and testing procedure was applied to 39 different data sets, each containing data for multiple groups, from a wide variety of industries. For these data, the testing procedure generally resulted in the same conclusion regarding overexposure under both models, even in those data sets where the within-worker variance components appeared to be quite heterogeneous. We also conducted a small simulation study to estimate the significance level of the proposed testing procedure, and found that the significance levels tended to be adequately close to the specified nominal level when a likelihood ratio test with significance level of at least 0.01 was used as a preliminary test. Additionally, we make specific recommendations for designing studies and suggest a method for determining whether engineering and administrative controls or individual-level interventions would be of most benefit to an overexposed group of workers.

Humans↗

PubMed2000

Meta-analyses of the relation between silicone breast implants and the risk of connective-tissue diseases.

BACKGROUND: The postulated relation between silicone breast implants and the risk of connective-tissue and autoimmune diseases has generated intense medical and legal interest during the past decade. The salience of the issue persists, despite the fact that a great deal of research has been conducted on this subject. To provide a stronger quantitative basis for addressing the postulated relation, we applied several techniques of meta-analysis that combine, compare, and summarize the results of existing relevant studies. METHODS: We searched data bases and reviewed citations in relevant articles to identify studies that met prestated inclusion criteria. Nine cohort studies, nine case-control studies, and two cross-sectional studies were included in our meta-analyses. We conducted meta-analyses of the results of these studies, both with and without adjustment for confounding factors, and a separate analysis restricted to studies of silicone-gel-filled breast implants. Finally, we estimated the annual number of new cases of connective-tissue disease that could be attributed to breast implants. RESULTS: There was no evidence that breast implants were associated with a significant increase in the summary adjusted relative risk of individual connective-tissue diseases (rheumatoid arthritis, 1.04 [95 percent confidence interval, 0.72 to 1.51]; systemic lupus erythematosus, 0.65 [95 percent confidence interval, 0.35 to 1.23]; scleroderma or systemic sclerosis, 1.01 [95 percent confidence interval, 0.59 to 1.73]; and Sjögren's syndrome, 1.42 [95 percent confidence interval, 0.65 to 3.11]); all definite connective-tissue diseases combined (0.80; 95 percent confidence interval, 0.62 to 1.04); or other autoimmune or rheumatic conditions (0.96; 95 percent confidence interval, 0.74 to 1.25). Nor was there evidence of significantly increased risk in the unadjusted analyses or in the analysis restricted to silicone-gel-filled implants. CONCLUSIONS: On the basis of our meta-analyses, there was no evidence of an association between breast implants in general, or silicone-gel-filled breast implants specifically, and any of the individual connective-tissue diseases, all definite connective-tissue diseases combined, or other autoimmune or rheumatic conditions. From a public health perspective, breast implants appear to have a minimal effect on the number of women in whom connective-tissue diseases develop, and the elimination of implants would not be likely to reduce the incidence of connective-tissue diseases.

Autoimmune Diseases↗

PubMed2000

Stability of hemoglobin and albumin adducts of benzene oxide and 1,4-benzoquinone after administration of benzene to F344 rats.

The stability of cysteinyl adducts of benzene oxide (BO) and mono-S-substituted cysteinyl adducts of 1,4-benzoquinone (1,4-BQ) was investigated in both hemoglobin (Hb) and albumin (Alb) following administration of a single oral dose of 400 mg [U-14C/13C6]benzene/kg body weight to F344 rats. Total radiobound adducts to Hb were stable, as were adducts formed by the reaction of [13C6]BO with cysteinyl residues on Hb. In both cases adduct stability was indicated by zero-order kinetics with decay rates consistent with the lifetime of rat erythrocytes. Hb adducts of 1,4-BQ were not detected, possibly due to the production of multi-S-substituted adducts within the erythrocyte. Regarding Alb binding, total radiobound adducts decayed more rapidly than expected (half-life of 0.4 days), suggesting that uncharacterized benzene metabolites were noncovalently bound or formed unstable adducts with Alb. Although adducts from reactions of BO and 1,4-BQ with Alb both decayed with rates consistent with those of Alb turnover in the rat, the half-life for 1,4-BQ-Alb (2.5 days) was shorter than that for BO-Alb (3.1 days), suggesting some instability of 1,4-BQ-Alb. Assuming similar rates of adduct instability in humans and rats, the 1,4-BQ-Alb adducts would be eliminated with a half-life of approximately 8 days, compared with BO-Alb, which would be expected to turnover with Alb (half-life of approximately 21 days).

Albumins↗

PubMed1999

Sexual behaviors and reproductive health outcomes: associations with wife abuse in India.

CONTEXT: Wife abuse has been associated with a variety of health concerns. Associations between abuse and reproductive health in India are not well known. OBJECTIVE: To examine relationships between men's reports of wife abuse and reproductive health issues in northern India. DESIGN: Structured face-to-face interviews were conducted as part of the male reproductive health supplement of the PERFORM System of Indicators Survey, a systematic multistage survey conducted in 1995-1996. SETTING: The northern state of Uttar Pradesh, one of the least developed states in India. PARTICIPANTS: A total of 6632 married men aged 15 to 65 years who lived with their wives and completed all survey questions for the study variables reported here. MAIN MEASURES: Physically and sexually abusive behaviors toward wives, sexual activities outside marriage, sexually transmitted disease (STD) symptoms, contraception use, unplanned pregnancies, and sociodemographic characteristics. RESULTS: Fifty-four percent of men reported not abusing their wives, while 17% reported physically but not sexually abusing their wives, 22% reported sexual abuse without physical force, and 7% reported sexual abuse with physical force. Abuse was more common among men who had extramarital sex (for sexual abuse using force: odds ratio [OR], 6.22; 95% confidence interval [CI], 3.98-9.72). Similarly, men who had STD symptoms were more likely to abuse their wives (with current symptoms: OR, 2.43; 95% CI, 1.73-3.42). Unplanned pregnancies were significantly more common among wives of abusive men, especially sexually abusive men who used force (OR, 2.62; 95% CI, 1.91-3.60). CONCLUSIONS: Wife abuse appears to be fairly common in northern India. Our findings that abusive men were more likely to engage in extramarital sex and have STD symptoms suggest that these men may be acquiring STDs from their extramarital relationships, thereby placing their wives at risk for STD acquisition, sometimes via sexual abuse. These abusive sexual behaviors also may result in an elevated rate of unplanned pregnancies.

Adolescent↗

PubMed1999

Sample size determination for multiple comparison studies treating confidence interval width as random.

Methods for optimal sample size determination are developed using four popular multiple comparison procedures (Scheffe's, Bonferroni's, Tukey's and Dunnett's procedures), where random samples of the same size n are to be selected from k (>/=2) normal populations with common variance sigma2, and where primary interest concerns inferences about a family of L linear contrasts among the k population means. For a simultaneous coverage probability of (1-alpha), the optimal sample size is defined to be the smallest integer value n*m such that, simultaneously for all L confidence intervals, the width of the lth confidence interval will be no greater than tolerance 2deltal (l=1,2,...,L) with tolerance probability at least (1-gamma), treating the pooled sample variance S2p as a random variable. Using Scheffe's procedure as an illustration, comparisons are made to usual sample size methods that incorrectly ignore the stochastic nature of S2p. The latter approach can lead to serious underestimation of required sample sizes and hence to unacceptably low values of the actually tolerance probability (1-gamma'). Our approach guarantees a lower bound of [1-(alpha+gamma)] for the probability that the L confidence intervals will both cover the parametric functions of interest and also be sufficiently narrow. Recommendations are provided regarding the choices among the four multiple comparison procedures for sample size determination and inference-making.

Confidence Intervals↗

PubMed1999

Violence victimization experiences of pregnant prisoners.

The violence victimization histories of pregnant incarcerated women were studied in relation to those of pregnant health department patients in North Carolina. Prisoners were twice as likely as health department patients to have experienced both physical and sexual violence compared to no violence, and over three times more likely to have experienced both types of violence compared to only one type. Implications for research and program development are noted.

Adolescent↗

PubMed1999

Violence in the lives of pregnant teenage women: associations with multiple substance use.

Using data from a consecutive sample of approximately 700 prenatal patients aged 12 to 19, the extent of violence and substance use in the lives of these women was examined, as were associations between violence and substance use. The findings show that 29% of the study participants had been victims of violence, with 15% experiencing physical violence only, 5% sexual violence only, and 9% both physical and sexual violence. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) from logistic regression analyses showed that, after controlling for confounding factors, victims were more likely than nonvictims to use cigarettes, alcohol, and illicit drugs, with victims of both physical and sexual violence being the most likely to use each type of substance. Ordinal logistic regression analysis found that, compared to nonvictims, violence victims were more likely to have more severe patterns of substance use (use multiple types of substances), with victims of both physical and sexual violence being the most likely to be multiple substance users. These findings underline the importance of both violence and substance use as health concerns among our youth.

Adolescent↗

PubMed1999

An investigation of factors contributing to styrene and styrene-7,8-oxide exposures in the reinforced-plastics industry.

During the manufacturing of reinforced plastics, large amounts of styrene and trace quantities of styrene-7,8-oxide (SO) are released. Since previous work suggests that inhalation of even small amounts of SO might be an important health risk, we investigated several possible factors contributing to styrene and SO exposure during the manufacture of reinforced plastics. Factors related to job type, worker and the type and quantity of styrene-containing resins were investigated using mixed-effects multiple linear regression models. Overall, SO exposure levels were positively correlated with styrene exposure levels. However, this correlation was statistically significant only among hand laminators who had the highest exposures to both styrene and SO. An important factor for predicting both styrene and SO concentrations was the type of resin used, while the quantity of resin consumed was predictive of styrene but not of SO exposure. Since So exposure appears to be associated with factors other than coexposure to styrene, more effort should be placed on investigating emissions of SO per se. The type of mixed-models regression analysis employed in this study can be used for clarifying the underlying patterns for exposures to styrene and SO as well as for evaluating preventive measures.

Carcinogens↗

PubMed1998

Individual-based and group-based occupational exposure assessment: some equations to evaluate different strategies.

Basically, two strategies can be considered for the analysis of hazardous pollutants in the work environment: group-based and individual-based strategies. This paper provides existing and recently derived equations for both strategies describing the influence of several factors on attenuation and on the standard error of an estimated linear regression coefficient relating a continuous exposure variable and a continuous health outcome via a simple linear regression model. We applied these equations using exposure variability information from industry-wide surveys over the past decade in order to gain more insight into the effects of various sources of exposure variability on choices among different analysis strategies. In general, for the modeling scenario considered here, there is not a straightforward criterion for choosing an optimal analysis strategy. Researchers have to decide between individual-based strategies generating precise, though biased, estimates or group-based strategies generating less precise but essentially unbiased estimates. For most exposure variability scenarios evaluated, an individual-based strategy yielded substantial attenuation. It is the authors' contention that the choice between individual-based and group-based strategies should be based on validity, rather than on precision, of the estimated exposure-response coefficient.

Air Pollutants, Occupational↗

PubMed1998

Comprehensive evaluation of long-term trends in occupational exposure: Part 1. Description of the database.

OBJECTIVES: To conduct a comprehensive evaluation of long term changes in occupational exposure among a broad cross section of industries worldwide. METHODS: A review of the scientific literature identified studies that reported historical changes in exposure. About 700 sets of data from 119 published and several unpublished sources were compiled. Data were published over a 30 year period in 25 journals that spanned a range of disciplines. For each data set, the average exposure level was compiled for each period and details on the contaminant, the industry and location, changes in the threshold limit value (TLV), as well as the type of sampling method were recorded. Spearman rank correlation coefficients were used to identify monotonic changes in exposure over time and simple linear regression analyses were used to characterise trends in exposure. RESULTS: About 78% of the natural log transformed data showed linear trends towards lower exposure levels whereas 22% indicated increasing trends. (The Spearman rank correlation analyses produced a similar breakdown between exposures monotonically increasing or decreasing over time.) Although the rates of reduction for the data showing downward trends ranged from -1% to -62% per year, most exposures declined at rates between -4% and -14% per year (the interquartile range), with a median value of -8% per year. Exposures seemed to increase at rates that were slightly lower than those of exposures which have declined over time. Data sets that showed downward (versus upward) trends were influenced by several factors including type and carcinogenicity of the contaminant, type of monitoring, historical changes in the threshold limit values (TLVs), and period of sampling. CONCLUSIONS: This review supports the notion that occupational exposures are generally lower today than they were years or decades ago. However, such trends seem to have been affected by factors related to the contaminant, as well as to the period and type of sampling.

Databases, Bibliographic↗