The end of world population growth

There has been enormous concern about the consequences of human population growth for the environment and for social and economic development. But this growth is likely to come to an end in the foreseeable future. Improving on earlier methods of probabilistic forecasting, here we show that there is around an 85 per cent chance that the world's population will stop growing before the end of the century. There is a 60 per cent probability that the world's population will not exceed 10 billion people before 2100, and around a 15 per cent probability that the world's population at the end of the century will be lower than it is today. For different regions, the date and size of the peak population will vary considerably.

Lung cancer among industrial sand workers exposed to crystalline silica

In 1997, the International Agency for Research on Cancer determined that crystalline silica was a human carcinogen but noted inconsistencies in the epidemiology. There are few exposure-response analyses. The authors examined lung cancer mortality among 4,626 industrial sand workers, estimating exposure via a job-exposure matrix based on 4,269 industrial hygiene samples collected in 1974--1995. The average length of employment was 9 years, and estimated average exposure was 0.05 mg/m(3) (the National Institute of Occupational Safety and Health Recommended Exposure Limit). Results confirmed excess mortality from silicosis/pneumoconioses (standardized mortality ratio = 18.2, 95% confidence interval: 10.6, 29.1; 17 deaths). The lung cancer standardized mortality ratio was 1.60 (95% confidence interval: 1.31, 1.93; 109 deaths). Limited data suggested that smoking might account for 10--20% of the lung cancer excess. Exposure-response analyses by quartile of cumulative exposure (15-year lag) yielded standardized rate ratios of 1.00, 0.78, 1.51, and 1.57 (p for trend = 0.07). Nested case-control analyses after exclusion of short-term workers, who had high overall morality, yielded odds ratios by quartile of cumulative exposure (15-year lag) of 1.00, 1.35, 1.63, and 2.00 (p for trend = 0.08) and odds ratios by quartile of average exposure of 1.00, 0.92, 1.44, and 2.26 (p = 0.005). These data lend support to the labeling by the International Agency for Research on Cancer of silica as a human carcinogen. There are approximately 2 million US workers exposed to silica; 100,000 are exposed to more than 0.1 mg/m(3).

Nutrition can modulate the toxicity of environmental pollutants: implications in risk assessment and human health

BACKGROUND

The paradigm of human risk assessment includes many variables that must be viewed collectively in order to improve human health and prevent chronic disease. The pathology of chronic diseases is complex, however, and may be influenced by exposure to environmental pollutants, a sedentary lifestyle, and poor dietary habits. Much of the emerging evidence suggests that nutrition can modulate the toxicity of environmental pollutants, which may alter human risks associated with toxicant exposures.

OBJECTIVES

In this commentary, we discuss the basis for recommending that nutrition be considered a critical variable in disease outcomes associated with exposure to environmental pollutants, thus establishing the importance of incorporating nutrition within the context of cumulative risk assessment.

DISCUSSION

A convincing body of research indicates that nutrition is a modulator of vulnerability to environmental insults; thus, it is timely to consider nutrition as a vital component of human risk assessment. Nutrition may serve as either an agonist or an antagonist (e.g., high-fat foods or foods rich in antioxidants, respectively) of the health impacts associated with exposure to environmental pollutants. Dietary practices and food choices may help explain the large variability observed in human risk assessment.

CONCLUSION

We recommend that nutrition and dietary practices be incorporated into future environmental research and the development of risk assessment paradigms. Healthful nutrition interventions might be a powerful approach to reduce disease risks associated with many environmental toxic insults and should be considered a variable within the context of cumulative risk assessment and, where appropriate, a potential tool for subsequent risk reduction.

Doubling of world population unlikely

Most national and international agencies producing population projections avoid addressing explicitly the issue of uncertainty. Typically, they provide either a single projection or a set of low, medium and high variants, and only very rarely do they give these projections a probabilistic interpretation. Probabilistic population projections have been developed for specific industrialized countries, mostly the United States, and are based largely on time-series analysis. On a global level, time-series analysis is not applicable because there is a lack of appropriate data, and for conceptual reasons such as the structural discontinuity caused by the demographic transition. Here we report on a new probabilistic approach that makes use of expert opinion on trends in fertility, mortality and migration, and on the 90 per cent uncertainty range of those trends in different parts of the world. We have used simulation techniques to derive probability distributions of population sizes and age structures for 13 regions of the world up to the year 2100. Among other things, we find that there is a probability of two-thirds that the world's population will not double in the twenty-first century.

Kidney disease and arthritis in a cohort study of workers exposed to silica

Silica exposure has been associated with kidney disease and rheumatoid arthritis; an autoimmune mechanism has been proposed. Approximately 2 million people are occupationally exposed to silica in the United States, 100,000 at more than twice the National Institute for Occupational Safety and Health recommended exposure limit of 0.05 mg/m(3). We examined renal disease morbidity and mortality, as well as arthritis mortality, in a cohort of 4,626 silica-exposed workers in the industrial sand industry (an industry previously unstudied). We compared the cohort with the U.S. population and also conducted internal exposure-response analyses using a job-exposure matrix based on more than 4,000 industrial hygiene samples. We found excess mortality from acute renal disease [standardized mortality ratio (SMR) = 2.61, 95% confidence intervals (95% CIs) = 1.49--4.24; 16 deaths], chronic renal disease (SMR = 1.61, 95% CI = 1.13--2.22; 36 deaths), and arthritis (SMR = 4.36, 95% CI = 2.76--6.54; 23 deaths) on the basis of multiple-cause mortality data, which considered any mention of disease on a death certificate. Linking the cohort with the U.S. registry of end-stage renal disease for the years 1977-1996, we found an excess of end-stage renal disease incidence (standardized incidence ratio = 1.97, 95% CI = 1.25--2.96; 23 cases), which was highest for glomerulonephritis (standardized incidence ratio = 3.85, 95% CI = 1.55--7.93; 7 cases). We found increasing end-stage renal disease incidence with increasing cumulative exposure; standardized rate ratios by quartile of cumulative exposure were 1.00, 3.09, 5.22, and 7.79. A positive exposure-response trend was also observed for rheumatoid arthritis on the basis of death certificate data. These data represent the largest number of kidney disease cases analyzed to date in a cohort with well-defined silica exposure and suggest a causal link between silica and kidney disease. Excess risk of end-stage renal disease due to a lifetime of occupational exposure at currently recommended limits is estimated to be 14%, above a background end-stage renal disease risk of 2%.

Pesticide use and practices in an Iowa farm family pesticide exposure study

Residents of Iowa were enrolled in a study investigating differences in pesticide contamination and exposure factors between 25 farm homes and 25 non-farm homes. The target pesticides investigated were atrazine, metolachlor, acetochlor, alachlor, 2,4-D, glyphosate, and chlorpyrifos; all were applied to either corn or soybean crops. A questionnaire was administered to all participants to determine residential pesticide use in and around the home. In addition, a questionnaire was administered to the farmers to determine the agricultural pesticides they used on the farm and their application practices. Non-agricultural pesticides were used more in and around farm homes than non-farm homes. Atrazine was the agricultural pesticide used most by farmers. Most farmers applied pesticides themselves but only 10 (59%) used tractors with enclosed cabs, and they typically wore little personal protective equipment (PPE). On almost every farm, more than one agricultural pesticide was applied. Corn was grown by 23 (92%) farmers and soybeans by 12 (48%) farmers. Of these, 10 (40%) grew both soybeans and corn, with only 2 (8%) growing only soybeans and 13 (52%) growing only corn. The majority of farmers changed from their work clothes and shoes in the home, and when they changed outside or in the garage, they usually brought their clothes and shoes inside. Applying pesticides using tractors with open cabs, not wearing PPE, and changing from work clothes in the home may increase pesticide exposure and contamination. Almost half of the 66 farm children less than 16 years of age were engaged in some form of farm chores, with 6 (9%) potentially directly exposed to pesticides, while only 2 (4%) of the 52 non-farm children less than 16 years of age had farm chores, and none were directly exposed to pesticides. Farm homes may be contaminated with pesticides in several ways, resulting in potentially more contamination than non-farm homes, and farm children may be directly exposed to pesticides through farm chores involving pesticides. In addition to providing a description of pesticide use, the data presented here will be useful in evaluating potential contributing factors to household pesticide contamination and family exposure.

What about the Rest of Them? Fatal Injuries Related to Production Agriculture Not Captured by the Bureau of Labor Statistics (BLS) Census of Fatal Occupational Injuries (CFOI)

Surveillance of injuries in production agriculture is necessary to inform stakeholders about workplace hazards and risks in order to improve and advance injury prevention policies and practices for this dangerous industry. The most comprehensive fatal injury surveillance effort currently in the United States is the Bureau of Labor Statistics (BLS) Census of Fatal Occupational Injuries (CFOI), which covers occupational fatalities in all U.S. industries, including production agriculture. However, this surveillance does not include many categories of fatalities that occur during agricultural work or on production agriculture worksites. To better capture the human cost of production agriculture, the authors of this paper call for the collection of additional data with a broader scope that supplements, not replaces, the current CFOI. This paper describes challenges in surveillance, highlights key procedural gaps, and offers recommendations for advancing national surveillance of fatal traumatic injuries associated with production agriculture.

Outbreak of hypersensitivity pneumonitis among mushroom farm workers

Between April 1982 and August 1985, seven cases of mushroom worker's lung (MWL), a form of hypersensitivity pneumonitis, were diagnosed among workers at one mushroom farm in Florida. The cases suffered from episodic shortness of breath, cough, fever and chills, myalgia, malaise, and difficulty breathing. Pulmonary function testing revealed restrictive ventilatory impairment and reduced diffusing capacity; chest radiographs exhibited diffuse interstitial pulmonary infiltrates. The seven cases occurred among workers from different farm operations, suggesting that workers throughout the farm were exposed to the disease causing agent(s). Six of the affected workers left employment at the farm in order to remain free of symptoms. The other affected worker was able to continue working at the farm, but only by remaining in a maintenance shop which was physically separated from the rest of the farm facilities. An industrial hygiene survey demonstrated that farm workers from every work area were exposed to organic dust constituents suspected of causing MWL, but no specific antigens were identified as the cause of the cases. Of the remaining workers who participated in a cross-sectional respiratory morbidity survey at the farm, approximately 20% of the more heavily exposed workers reported occasionally experiencing symptoms consistent with MWL. Approximately 10% of the workers had below normal spirometry test results, but interpretation was hampered by the diverse racial makeup of the population and lack of an adequate comparison group. No abnormalities consistent with either acute or chronic MWL were seen on the chest radiographs. Serologic tests demonstrated that almost all workers had been exposed to antigens capable of causing MWL, but the results were not associated with health status. At the time of the cross-sectional survey, no workers were found to be suffering acute respiratory problems consistent with MWL.

Noise exposures of rural adolescents

PURPOSE

This project was conducted to characterize the noise exposure of adolescents living in rural and agricultural environments.

METHODS

From May to October, 25 adolescents ages 13 through 17, living either on a farm or a rural nonfarm, were enrolled in the study. Subjects received training on the correct operation and use of personal noise dosimeters and the proper way to record their daily tasks on activity cards. Subjects completed 4 days of self-monitoring noise dosimetry, 2 days in the first round (May-July) and 2 days in the second round (August-October). In addition to dosimetry, subjects completed activity logs of their daily tasks.

RESULTS

The mean daily noise exposures of adolescents living on farms and in nonfarm rural homes were between 55.4 dBA (A-weighted decibels) and 103.5 dBA, with 44% of the daily measurements greater than the National Institute of Occupational Safety and Health Recommended Exposure Level of 85 dBA. Task-based analysis of noise exposures found that activities involving mechanized equipment resulted in the highest exposures, while activities in the home resulted in the lowest exposure. No particular demographic group had a statistically higher noise exposure; therefore, specific factors apart from activities and noise sources could not be identified as risk factors for exposure to hazardous noise levels.

CONCLUSIONS

The results of this project indicate that rural adolescents complete a variety of activities and are exposed to noise sources with a broad range of decibel levels. While the exposures may change from day to day, there are occasions when exposure to noise exceeds the recommended levels.

Hassles and uplifts associated with caring for people with cognitive impairment in community settings

In this study we explored the hassles and uplifts (i.e. negative and positive emotional events) experienced by registered nurses, nursing assistants and personal carers working with people with cognitive impairment in community and residential healthcare settings in Brisbane, Queensland, Australia. The primary aim of the research was to explore what aspects of caring for cognitively impaired clients hassles nurses, what helps to relieve these hassles, what aspects of this work nurses find rewarding and what detracts from those rewards, as well as the intensity with which each of these aspects were felt. A questionnaire developed to explore hassles and uplifts at work was administered and 57 responses obtained. Results indicated that caring for the cognitively impaired client provides many uplifts for nurses and few hassles. However, the hassles that occurred were of high importance. This paper will be of interest to managers, nurses and carers in settings where there are people with cognitive impairment as well as scholars, who may find that assessing emotional hassles and uplifts provides additional insights into other areas of nursing.

A case-control study of trace-element status and lung cancer in Appalachian Kentucky

Appalachian Kentucky (App KY) leads the nation in lung cancer incidence and mortality. Trace elements, such as As, have been associated with lung cancers in other regions of the country and we hypothesized that a population-based study would reveal higher trace element concentrations in App KY individuals with cancer compared to controls. Using toenail and drinking water trace element concentrations, this study investigated a possible association between lung cancer incidence and trace-element exposure in residents of this region. This population-based case-control study had 520 subjects, and 367 subjects provided toenail samples. Additionally, we explored the relationship between toenail and fingernail trace-element concentrations to determine if fingernails could be used as a surrogate for toenails when patients are unable to provide toenail samples. We found that, contrary to our initial hypothesis, trace element concentrations (Al, As, Cr, Mn, Co, Fe, Ni, Cu, Se, and Pb) were not higher in cancer cases than controls with the exception of Zn where concentrations were slightly higher in cases. In fact, univariate logistic regression models showed that individuals with lower concentrations of several elements (Al, Mn, Cr, and Se) were more likely to have lung cancer, although only Mn was significant in multivariate models which controlled for confounding factors. While drinking water concentrations of Al, Cr and Co were positively related to cancer incidence in univariate models, only Co remained significant in multivariate models. However, since the drinking water concentrations were extremely low and not reflected in the toenail concentrations, the significance of this finding is unclear. We also found that fingernail concentrations were not consistently predictive of toenail concentrations, indicating that fingernails should not be used as surrogates for toenails in future studies.

Impact of a worker notification program: assessment of attitudinal and behavioral outcomes

BACKGROUND

Hundreds of worker notification programs are conducted each year to communicate occupational risks to workers. However, few attempts have been made to evaluate their effectiveness and few have described how communication theories are applied in developing notification messages. We developed and assessed the effectiveness of a worker notification program at a beryllium machining plant.

METHODS

We compared self-protective attitudinal and behavioral responses among workers in two plants: (1) an intervention plant that received beryllium risk notification and (2) a matched control plant that did not receive notification.

RESULTS

Workers receiving notification reported significantly stronger perceptions of threat and efficacy, more positive attitudes toward safety practices, and engaged in more protective behaviors than the workers at the control plant.

CONCLUSIONS

This study demonstrates the utility of applying communication theories in the development of notification messages and the results suggest that mass presentations may be just as effective, if not more so, than one-on-one notifications. Am. J. Ind. Med. 37:205-213, 2000. Published 2000 Wiley-Liss, Inc.

Determinants of atrazine contamination in the homes of commercial pesticide applicators across time

Twenty-nine commercial pesticide applicator households in eastern Iowa were enrolled to investigate in-home contamination of atrazine, the most commonly used corn herbicide in the Unites States. From each home, four vacuum dust samples were collected during atrazine application season (Visit 1) and again 6 months later during winter months (Visit 2). Samples were taken from the following locations: primary entryway for pesticide applicator, living room, master bedroom, and kitchen. The applicator completed an atrazine handling log and household questionnaire with spouse. Of the 230 dust samples, only 2 were below the level of detection, 2 ng of atrazine per gram (ng/g) of fine dust (dust particle size 5-150 μm). Dust levels were standardized to chemical loading. During application season the entryway (2.68 ng/cm(2)) and kitchen (0.47 ng/cm(2)) had the highest geometric mean atrazine chemical loading. The entryway chemical loading during Visit 2 was the second highest aggregate (0.55 ng/cm(2)). Aggregate concentrations were significantly higher at Visit 1 compared with Visit 2 when paired by location (p≤0.02). Analysis showed that job (application, mixing/loading, or both) was not associated with in-home atrazine contamination. Linear regression showed a strong positive association between atrazine handling (number of acres applied with atrazine, number of days atrazine handled, and pounds of atrazine handled) and aggregate dust chemical loading from both visits (p = 0.06, 0.03, and 0.10, respectively). Frequency of vacuuming was inversely associated with Visit 2 concentrations (p = 0.10) and showed a weaker association with Visit 1 (p = 0.30). Removing shoes outside the home was associated with lower atrazine chemical loading (p = 0.03), and applicators changing work clothes in the master bedroom had significantly increased atrazine chemical loading in master bedrooms (p = 0.01). Changes in hygiene practices for commercial pesticide applicators could significantly reduce atrazine and, likely, other pesticide contaminations in the home.

Academic psychiatry and managed care: a case study

An academic department of psychiatry in New York City eliminated the need for behavioral managed care intermediaries by transforming itself from a fee-for-service system to a system able to engage in full-risk capitation contracts. The first step was to require health maintenance organizations to contract directly with the department. The department formed two legal entities, a behavioral management services organization for utilization management and a behavioral integrated provider association. The authors describe these entities and review the first year of operation, presenting data on enrollees, capitation rates, and service utilization for the first three contracts. The fundamental differences in the treatment model under managed care and under a fee-for-service system are highlighted. The authors conclude that by contracting directly with insurers on a full-risk capitation basis, departments of psychiatry will be better able to face the economic threats posed by the cost constraints inherent in managed care and maintain or re-establish their autonomy as care managers as well as high-quality care providers.

Paternal and joint parental occupational pesticide exposure and spina bifida in the National Birth Defects Prevention Study, 1997 to 2002

BACKGROUND

Because of persistent concerns over the association between pesticides and spina bifida, we examined the role of paternal and combined parental occupational pesticide exposures in spina bifida in offspring using data from a large population-based study of birth defects.

METHODS

Occupational information from fathers of 291 spina bifida cases and 2745 unaffected live born control infants with estimated dates of delivery from 1997 to 2002 were collected by means of maternal report. Two expert industrial hygienists estimated exposure intensity and frequency to insecticides, herbicides, and fungicides. Multivariable logistic regression models were used to estimate adjusted odds ratios (aOR) and 95% confidence intervals (CI) for exposure to any pesticide and to any class of pesticide (yes/no; and by median), and exposure to combinations of pesticides (yes/no) and risk of spina bifida. Adjusted odds ratios were also estimated by parent exposed to pesticides (neither, mother only, father only, both parents).

RESULTS

Joint parental occupational pesticide exposure was positively associated with spina bifida (aOR, 1.5; 95% CI, 0.9-2.4) when compared with infants with neither maternal nor paternal exposures; a similar association was not observed when only one parent was exposed. There was a suggested positive association between combined paternal insecticide and fungicide exposures and spina bifida (aOR, 1.5; 95% CI, 0.8-2.8), however, nearly all other aORs were close to unity.

CONCLUSION

Overall, there was little evidence paternal occupational pesticide exposure was associated with spina bifida. However, the small numbers make it difficult to precisely evaluate the role of pesticide classes, individually and in combination. Birth Defects Research (Part A) 106:963-971, 2016. © 2016 Wiley Periodicals, Inc.

Late-Stage Melanoma: Be Sure to Screen Uninsured, Unmarried Men

OBJECTIVE

The purpose of this study was to assess for any associations between individual and social factors and late-stage melanoma in Kentucky from 1995 to 2013.

METHODS

The study combines three datasets: individual-level data from the Kentucky Cancer Registry, census tract-level data from the US Census, and county-level physician licensure data from the Kentucky Department for Public Health. The study population is described by all cases, early stage, and late stage. Logistic regression was used to evaluate the unadjusted associations between each covariate and early-stage and late-stage disease groups. All of the significant variables were assessed for interaction effect, and the significant interaction terms were used in the final model. Multiple logistic regression provided the final model of late-stage disease.

RESULTS

In this study population, a dramatic increase in melanoma incidence is seen from 1995 to 2013 with a threefold increase in the number of cases per year. Of the 10,109 cases reported, 13.6% have late-stage disease, with a mean age for all cases at 56.9 years and the majority being men. Late-stage cases are more commonly uninsured or insured with Medicaid or Medicare compared with cases with early-stage lesions. Having a spouse or partner is clearly protective from being diagnosed as having late-stage melanoma, whereas being uninsured or having Medicaid increases the odds of late-stage melanoma.

CONCLUSIONS

The incidence of melanoma is increasing dramatically. With no screening recommendation for the general population from the US Preventive Task Force, clinicians should focus on those at increased risk of late-stage melanoma: unmarried men who are uninsured or receiving Medicaid.

Association between maternal occupational exposure to polycyclic aromatic hydrocarbons and rare birth defects of the face and central nervous system

BACKGROUND

Previous studies suggested associations between maternal smoking, a source of exposure to polycyclic aromatic hydrocarbons (PAHs) and other chemicals, and central nervous system and face birth defects; however, no previous studies have evaluated maternal occupational PAH exposure itself.

METHODS

Jobs held in the periconceptional period were retrospectively assigned for occupational PAH exposures. Associations between maternal occupational PAH exposure and selected rare defects of the face (cataracts, microphthalmia, glaucoma, microtia, and choanal atresia) and central nervous system (holoprosencephaly, hydrocephaly, cerebellar hypoplasia, and Dandy-Walker malformation) were evaluated using data from the National Birth Defects Prevention Study, a population-based case-control study in the United States. Crude and adjusted odds ratios (ORs) with 95% confidence intervals were calculated to estimate associations between each evaluated defect and PAH exposure using multivariable logistic regression.

RESULTS

Food and beverage serving, as well as cooks and food preparation occupations, were among the most frequent jobs held by exposed mothers. Cataracts, microtia, microphthalmia, and holoprosencephaly were significantly associated with PAH exposure with evidence of dose-response (P-values for trend ≤.05). Hydrocephaly was associated with any PAH exposure, but not significant for trend. Sensitivity analyses that reduced possible sources of exposure misclassification tended to strengthen associations.

CONCLUSIONS

This is the first population-based case-control study to evaluate associations between maternal occupational PAH exposures and these rare birth defects of the central nervous system and face.

Spatial and seasonal variation in disinfection byproducts concentrations in a rural public drinking water system: A case study of Martin County, Kentucky, USA

To increase our understanding of the factors that influence formation of disinfection byproducts (DBPs) in rural drinking systems, we investigated the spatial and seasonal variation in trihalomethane (THM) and haloacetic acid (HAA) concentrations in relation to various chemical and physical variables in a rural public drinking water system in Martin County, Kentucky, USA. We collected drinking water samples from 97 individual homes over the course of one year and analyzed them for temperature, electrical conductivity, pH, free chlorine, total chlorine, THMs (chloroform, bromodichloromethane, dibromochloromethane, dichlorobromomethane, and bromoform) and HAAs (monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, bromoacetic acid, and dibromoacetic acid). Spatial autocorrelation analysis showed only weak overall clustering for HAA concentrations and none for THMs. The relationship between modeled water age and TTHM or HAA5 concentrations varied seasonally. In contrast, there was strong variation for both HAA and THMs, with concentrations of HAA peaking in mid-summer and THMs peaking in early fall. Multiple regression analysis revealed that THM concentrations were strongly correlated with conductivity, while HAA concentrations were more strongly correlated with water temperature. Individual DBP species that only contained chlorine halogen groups were strongly correlated with temperature, while compounds containing bromine were more strongly correlated with conductivity. Further investigation revealed that increased drinking water conductivity associated with low discharge of the Tug Fork River, the source water, is highly correlated with increased concentrations of bromide. Discharge and conductivity of the Tug Fork River changed dramatically through the year contributing to a seasonal peak in bromide concentrations in the late summer and early fall and appeared to be a driver of brominated THM concentrations. Brominated DBPs tend to have higher toxicity than DBPs containing only chlorine, therefore this study provides important insight into the seasonal factors driving risk from exposure to DBPs in rural drinking water systems impacted by bromide.

Testing and Validating Semi-automated Approaches to the Occupational Exposure Assessment of Polycyclic Aromatic Hydrocarbons

INTRODUCTION

When it is not possible to capture direct measures of occupational exposure or conduct biomonitoring, retrospective exposure assessment methods are often used. Among the common retrospective assessment methods, assigning exposure estimates by multiple expert rater review of detailed job descriptions is typically the most valid, but also the most time-consuming and expensive. Development of screening protocols to prioritize a subset of jobs for expert rater review can reduce the exposure assessment cost and time requirement, but there is often little data with which to evaluate different screening approaches. We used existing job-by-job exposure assessment data (assigned by consensus between multiple expert raters) from a large, population-based study of women to create and test screening algorithms for polycyclic aromatic hydrocarbons (PAHs) that would be suitable for use in other population-based studies.

METHODS

We evaluated three approaches to creating a screening algorithm: a machine-learning algorithm, a set of a priori decision rules created by experts based on features (such as keywords) found in the job description, and a hybrid algorithm incorporating both sets of criteria. All coded jobs held by mothers of infants participating in National Birth Defects Prevention Study (NBDPS) (n = 35,424) were used in developing or testing the screening algorithms. The job narrative fields considered for all approaches included job title, type of product made by the company, main activities or duties, and chemicals or substances handled. Each screening approach was evaluated against the consensus rating of two or more expert raters.

RESULTS

The machine-learning algorithm considered over 30,000 keywords and industry/occupation codes (separate and in combination). Overall, the hybrid method had a similar sensitivity (87.1%) as the expert decision rules (85.5%) but was higher than the machine-learning algorithm (67.7%). Specificity was best in the machine-learning algorithm (98.1%), compared to the expert decision rules (89.2%) and hybrid approach (89.1%). Using different probability cutoffs in the hybrid approach resulted in improvements in sensitivity (24-30%), without the loss of much specificity (7-18%).

CONCLUSION

Both expert decision rules and the machine-learning algorithm performed reasonably well in identifying the majority of jobs with potential exposure to PAHs. The hybrid screening approach demonstrated that by reviewing approximately 20% of the total jobs, it could identify 87% of all jobs exposed to PAHs; sensitivity could be further increased, albeit with a decrease in specificity, by adjusting the algorithm. The resulting screening algorithm could be applied to other population-based studies of women. The process of developing the algorithm also provides a useful illustration of the strengths and potential pitfalls of these approaches to developing exposure assessment algorithms.