Accurate Exposure Research Articles

A National Prediction Model for PM2.5Component Exposures and Measurement Error–Corrected Health Effect Inference

Background: Studies estimating health effects of long-term air pollution exposure often use a two-stage approach: building exposure models to assign individual-level exposures, which are then used in regression analyses. This requires accurate exposure modeling and careful treatment of exposure measurement error.Objective: To illustrate the importance of accounting for exposure model characteristics in two-stage air pollution studies, we considered a case study based on data from the Multi-Ethnic Study of Atherosclerosis (MESA).Methods: We built national spatial exposure models that used partial least squares and universal kriging to estimate annual average concentrations of four PM2.5 components: elemental carbon (EC), organic carbon (OC), silicon (Si), and sulfur (S). We predicted PM2.5 component exposures for the MESA cohort and estimated cross-sectional associations with carotid intima-media thickness (CIMT), adjusting for subject-specific covariates. We corrected for measurement error using recently developed methods that account for the spatial structure of predicted exposures.Results: Our models performed well, with cross-validated R2 values ranging from 0.62 to 0.95. Naïve analyses that did not account for measurement error indicated statistically significant associations between CIMT and exposure to OC, Si, and S. EC and OC exhibited little spatial correlation, and the corrected inference was unchanged from the naïve analysis. The Si and S exposure surfaces displayed notable spatial correlation, resulting in corrected confidence intervals (CIs) that were 50% wider than the naïve CIs, but that were still statistically significant.Conclusion: The impact of correcting for measurement error on health effect inference is concordant with the degree of spatial correlation in the exposure surfaces. Exposure model characteristics must be considered when performing two-stage air pollution epidemiologic analyses because naïve health effect inference may be inappropriate.Citation: Bergen S, Sheppard L, Sampson PD, Kim SY, Richards M, Vedal S, Kaufman JD, Szpiro AA. 2013. A national prediction model for PM2.5 component exposures and measurement error–corrected health effect inference. Environ Health Perspect 121:1017–1025; http://dx.doi.org/10.1289/ehp.1206010

Influence of recency and duration of glucocorticoid use on bone mineral density and risk of fractures: population-based cohort study

Although systemic glucocorticoids are commonly used, it is difficult to obtain accurate exposure history. In 50,000 patients, we confirmed that glucocorticoids were associated with reductions in bone mineral density (BMD) and increases in fracture and documented that recent and prolonged durations of exposure were particularly associated with adverse events-dose information did not improve risk prediction. Systemic glucocorticoid use, defined as ever having taken supra-physiologic doses for 90-days or more, is a risk factor for low BMD and fractures. This definition does not distinguish recent (vs remote) exposure. Within a population-based clinical BMD registry in Manitoba, Canada, we identified all adults over age 40 years tested between 1998 and 2007 and then undertook a cohort study. We identified all oral glucocorticoid dispensations from 1995 to 2009 and stratified exposure by timing ("recent" if within 12 months vs "remote") and duration (short [<90 days] vs prolonged [≥90 days]). Osteoporosis-related risk factors and treatments and major fractures were obtained using administrative health data. A total of 12,818 of 52,070 (25%) subjects had used glucocorticoids prior to BMD testing; the most common exposure was remote short (n = 6453) vs recent prolonged (n = 2896) vs recent short (n = 2644) vs remote prolonged (n = 825). Compared to 39,252 never-users, only recent prolonged glucocorticoid use was significantly associated with femoral neck T-score (ANCOVA-adjusted difference -0.13, 95% CI -0.16 to -0.10, p < 0.001). There were 2,842 major (566 hip) fractures over median 5-year follow-up. Compared with never-users, only recent prolonged glucocorticoid use was significantly associated with BMD-independent increases in risk of incident major fracture (5.4 vs 7.7%, adjusted HR 1.25, 95% CI 1.07-1.45, p = 0.004) and hip fracture (1.1 vs 1.8%, adjusted HR 1.61, 95% CI 1.18-2.20, p = 0.003). Recent and prolonged glucocorticoid use (but neither remote nor recent short courses) was independently associated with reduced BMD and increased risk of fractures. These findings should permit clinicians to identify a high-risk group of patients that might benefit from osteoporosis prevention.

Children living near chipboard and wood industries are at an increased risk of hospitalization for respiratory diseases: A prospective study

Pollutants emitted from wood processing factories may be harmful to the health of the population. The aim of this prospective cohort study was to evaluate whether proximity to wood factories was associated with the risk of hospital admissions in children living in the Viadana district (Italy), where two big chipboard industries and other smaller wood factories (sawmills, multi-strata layer manufacturing) are located. In 2006, children (3-14 years) living in the Viadana district were surveyed through a parental questionnaire (n=3854), their home/school addresses were geocoded and the distances to the wood industries were calculated. Hospital discharge records for the years 2007-2009 were obtained. Cox proportional hazard regression models were used to estimate the association between hospitalization rates and distance to the factories, adjusting for sex, age, nationality, parents' education, exposure to passive smoking and reported traffic near home. During the 3-year follow-up, the risk of hospitalization for all diagnoses (Hospitalization Hazard Ratio, HHR=1.55; 95% CI: 1.24-1.95) and for respiratory diseases (HHR=1.80; 95% CI: 1.14-2.86) was greater in the children living close (<2 km) to the chipboard industries, with respect to the children who lived at ≥2 km from any wood factory. The children living close to the smaller wood factories were also at increased risk of hospitalization for respiratory diseases (HHR=1.74; 95% CI: 1.06-2.85). This study highlights a health problem for the children living close to chipboard and wood factories in the Viadana district. Further research should develop accurate exposure models based on objective measurements of air pollution in order to confirm these findings.

Integration of a dynamic organism model into the DynA Model: Development and application to the case of DDT in Lake Maggiore, Italy

The Single Organism (SO) model was developed to investigate the influence of temporal dynamics of aquatic organism properties on their exposure to organic chemicals in water. SO was then integrated with an existing dynamic surface-water model (DynA), to form the coupled water-bioaccumulation model EcoDynA. In order to evaluate the model performance, the results produced by EcoDynA were compared to the p,p′-DDT concentrations measured in specimens of whitefish of different age and sex caught in Lake Maggiore after the discovery of a DDT spill. The comparison showed a good agreement. Other satisfying results were obtained comparing model results with p,p′-DDT concentration values measured in another species of whitefish which were available in the literature. A preliminary sensitivity analysis confirmed that accounting for dynamics of parameters such as organism lipid fraction and feeding rate is necessary to obtain accurate exposure predictions.

Retrospective exposure data for baby and children care products: An analysis of 48 clinical studies

To conduct a reliable safety assessment, accurate exposure information for cosmetic products and ingredients is needed. The aim of the present retrospective study was to determine the amount per application and the daily exposure for some of the most commonly used baby cosmetic products. Consumption data from 48 clinical studies performed on 1481 babies and children (from 0 to 10 years old) were reviewed and used to conduct a probabilistic evaluation of dermal exposure. Six categories of products were reviewed: rinseoff products for hair and body; rinse-off products for the whole body; leave-on products for face and body; cleansers for face and body; diaper dermatitis treatment products; shampoos. Subjects were provided with products and recorded detailed daily usage information over a 1-4-week period, depending on the study. Products were weighed at the start and upon completion of each study in order to determine the total amount of product used. The mean, median, standard deviation and 95th percentile were calculated for daily consumption and exposure, for several age groups from 0 to 10 years old. This study provides current baby cosmetic exposure information for commonly used products which will be useful for risk assessment purposes.

Progress in the Development of Federal Resources to Assess Dietary Supplement (DS) Exposures

Accurate total exposure estimates are necessary to examine the role of nutrients and bioactives with health outcomes, as well as to monitor safety.ObjectiveReview progress in the development of methods and databases to assess exposures from DS.MethodStakeholder meetings and workshops; and an ad hoc Federal Working Group suggest and guide product development.ResultsDS intakes have been added to the NHANES 24‐hr recall questionnaire. An analytically validated DS composition database (DS Ingredient Database) is publicly available through the NLM web portal, which contains adult and child multi‐vitamin and mineral (MVM) DS and calculators to compare declared label with estimated analytical values. OTC prenatal MVM and omega‐3 supplements are now being added. A DS Label Database is under development, with full label information from virtually all DS products offered for sale in the US, and links to a structured vocabulary for indexing DS. A MyDS app lets consumers’ record products they take.ConclusionThese resources will help researchers accurately assess exposure to nutrients and bioactives from DS. Funding: Office of Dietary Supplements, National Institutes of Health

Teeth as a biomarker of past chemical exposure

Accurate prenatal exposure assessment is one of the major challenges in environmental epidemiologic studies. Variations in placental transport make maternal biospecimens unreliable for many chemicals and fetal specimens collected at birth do not provide information on exposure timing over the prenatal period. The skeletal compartment is an important chemical repository, making calcified tissues important for measuring exposure. For decades teeth have been used to estimate long-term cumulative exposure to metals and some organic chemicals. Recently developed methodologies that combine sophisticated histological and chemical analysis to precisely sample tooth layers that correspond to specific life stages have the potential to reconstruct exposure in the second and third trimesters of prenatal development and during early childhood. Such a retrospective biomarker that precisely measures exposure intensity and timing during prenatal development would substantially aid epidemiologic investigations, particularly case-control studies of rare health outcomes.

Biomonitoring the Cooked Meat Carcinogen 2-Amino-1-Methyl-6-Phenylimidazo[4,5-b]Pyridine in Hair: Impact of Exposure, Hair Pigmentation, and Cytochrome P450 1A2 Phenotype

Hair is a promising tissue to assess exposure to 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a carcinogen formed in cooked meats. However, an understanding of how dietary exposure to PhIP, cytochrome P450 1A2 activity-a key enzyme involved in PhIP metabolism, and hair pigmentation affect the level of PhIP accrued in hair is required to determine the reliability of the PhIP hair level as a biomarker of exposure to this carcinogen. We examined the impact of PhIP exposure, cytochrome P450 1A2 activity, and hair pigmentation on the levels of PhIP accumulated in the hair of volunteers on a 4-week semicontrolled diet of cooked meat containing known quantities of PhIP. The amount of PhIP in hair increased, on average, 15-fold in light- and dark-haired individuals during consumption of cooked meat. PhIP levels in hair were correlated to PhIP intake (ρ = 0.53; P < 0.001), and the relationship was strengthened when PhIP levels were normalized for the melanin content of hair (ρ = 0.71; P < 0.001). However, PhIP accrual in hair was not correlated to cytochrome P450 1A2 activity, as assessed by the caffeine test, or to the levels of unmetabolized PhIP in urine or to the metabolic ratio of the major urinary metabolite N(2)-(β-1-glucosiduronyl-2-(hydroxyamino)-1-methyl-6-phenylimidazo[4,5-b]pyridine to unmetabolized PhIP. The use of the PhIP hair biomarker should take hair pigmentation into account for accurate exposure assessment of PhIP. PhIP hair levels can serve as a biomarker in epidemiologic studies investigating the association of heterocyclic aromatic amine (HAA), cooked meat, and cancer risk.

Assessment of human exposure level to PM10 in China

Epidemiological studies have found that atmospheric particulate matter, especially PM10 (inhalable particulate matter with aerodynamic diameter less than or equal to 10 μm) is one of the pollutants that are harmful to human health. In recent years, particulate matter pollution in China is becoming increasingly serious and PM10 has become the primary pollutant in Beijing and other cities. Therefore, it is necessary to carry out studies and a health damage assessment of PM10. In human health damage assessment, measuring human exposure level to PM10 is required and crucial to provide accurate exposure data for the exposure–response relationship, and also for the accurate quantitative assessment of human exposure.The spatial distribution of particle concentration in China is variable because of spatial differences in the local economic level and the geographical environment. Along with the accelerating urbanisation in China, city population density is high, and the population distribution is variable between and within cities, thus resulting in different population numbers exposed to different concentration ranges. Therefore, an accurate assessment of China's level of exposure to particulate matter is a priority and the basis for assessing the damage to public health caused by particle pollution.Using high accuracy population and PM10 monitoring data, this study analysed the human exposure to PM10 in different regions and typical cities of China. The results show that for most areas of China, the population-weighted PM10 exposure concentration is slightly higher than the annual mean concentration, meaning that more of the population is exposed to high concentrations, and most of the population is exposed to levels that meet the second national standard (between 40 and 100 μg m−3), occupying about 83.7% of population and 76.3% of area in China. The population exposure to PM10 is higher in two types of typical regions and cities: areas with dense human populations such as Jingjinji, Beijing and Tianjin, and areas with more sand dust and factories such as Northwest and Chongqing.

Exposure assessment of mobile phone base station radiation in an outdoor environment using sequential surrogate modeling

Human exposure to background radiofrequency electromagnetic fields (RF-EMF) has been increasing with the introduction of new technologies. There is a definite need for the quantification of RF-EMF exposure but a robust exposure assessment is not yet possible, mainly due to the lack of a fast and efficient measurement procedure. In this article, a new procedure is proposed for accurately mapping the exposure to base station radiation in an outdoor environment based on surrogate modeling and sequential design, an entirely new approach in the domain of dosimetry for human RF exposure. We tested our procedure in an urban area of about 0.04 km(2) for Global System for Mobile Communications (GSM) technology at 900 MHz (GSM900) using a personal exposimeter. Fifty measurement locations were sufficient to obtain a coarse street exposure map, locating regions of high and low exposure; 70 measurement locations were sufficient to characterize the electric field distribution in the area and build an accurate predictive interpolation model. Hence, accurate GSM900 downlink outdoor exposure maps (for use in, e.g., governmental risk communication and epidemiological studies) are developed by combining the proven efficiency of sequential design with the speed of exposimeter measurements and their ease of handling.

Contaminant intrusion in water distribution systems: An ingress model

In a water distribution system, low or negative pressure may occur under normal operation of the system and may lead to contaminant intrusion. To assess the risk associated with contaminant intrusion, exposure assessment is required. To have more accurate intrusion exposure assessment, the effects of the surrounding soil on the intrusion rate must be considered. This research proposes a model to create a more realistic estimation of intrusion rate. A two‐level factorial design was used to screen the effect of pipe internal pressure, soil porosity, average diameter of soil particles, size of the leak point, and pipe burial depth. The Buckingham p theorem was applied to group the influential factors into a set of dimensionless p parameters. The relationship among the p parameters was obtained by using the numerical data generated by a two‐dimensional finite element model for flow in a saturated zone surrounding a pipe. A regression analysis was then applied to find the best fit for the data.

Is Ambient PM 2.5 Sulfate Harmful?

Is Ambient PM _2.5 Sulfate Harmful?

조화상수를 이용한 조간대 노출시간 추정공식 개발

A new formulae for the estimation of the exposure duration in the inter-tidal zone are developed. The exposure duration is one of the most important factors influencing the habitat distribution of the benthic organisms. The formulae can estimate the exposure duration only using the four major tidal harmonic constants available in almost coastal areas. It is easier than the existing method using the frequency analysis of the hourly tidal elevation data. The estimation results by using the formulae suggested in this study are compared with the value by using the observed tidal elevation data analysis in the west coast, Korea. The mean RMS (root-mean squared) errors ranged form 0.8 to 1.4%. It can be used to simply estimate the accurate exposure duration in the region not having the longterm hourly tidal elevation data.

Land Use Regression 모델을 이용한 수도권 초등학교 대기오염 노출 분석

Epidemiologic studies of air pollution need accurate exposure assessments at unmonitored locations. A land use regression (LUR) model has been used successfully for predicting traffic-related pollutants, although its application has been limited to Europe, North America, and a few Asian region. Therefore, we modeled traffic-related pollutants by LUR then examined whether LUR models could be constructed using a regulatory monitoring network in Metropolitan area in Korea. We used the annual-mean nitrogen dioxide () in 2010 in the study area. Geographic variables that are considered to predict traffic-related pollutants were classified into four groups: road type, traffic intensity, land use, and elevation. Using geographical variables, we then constructed a model to predict the monitored levels of . The mean concentration of was 30.71 ppb (standard deviation of 5.95) respectively. The final regression model for the concentration included five independent variables. The LUR models resulted in of 0.59. The mean concentration of of elementary schools was 34.04 ppb (standard deviation of 5.22) respectively. The present study showed that even if we used regulatory monitoring air quality data, we could estimate moderately well. These analyses confirm the validity of land use regression modeling to assign exposures in epidemiological studies, and these models may be useful tools for assessing health effects of long-term exposure to traffic related pollution.

Characterization and Preliminary Toxicity Assay of Nano‐Titanium Dioxide Additive in Sugar‐Coated Chewing Gum

Nanotechnology shows great potential for producing food with higher quality and better taste through including new additives, improving nutrient delivery, and using better packaging. However, lack of investigations on safety issues of nanofood has resulted in public fears. How to characterize engineered nanomaterials in food and assess the toxicity and health impact of nanofood remains a big challenge. Herein, a facile and highly reliable separation method of TiO2 particles from food products (focusing on sugar-coated chewing gum) is reported, and the first comprehensive characterization study on food nanoparticles by multiple qualitative and quantitative methods is provided. The detailed information on nanoparticles in gum includes chemical composition, morphology, size distribution, crystalline phase, particle and mass concentration, surface charge, and aggregation state. Surprisingly, the results show that the number of food products containing nano-TiO2 (<200 nm) is much larger than known, and consumers have already often been exposed to engineered nanoparticles in daily life. Over 93% of TiO2 in gum is nano-TiO2 , and it is unexpectedly easy to come out and be swallowed by a person who chews gum. Preliminary cytotoxicity assays show that the gum nano-TiO2 particles are relatively safe for gastrointestinal cells within 24 h even at a concentration of 200 μg mL(-1) . This comprehensive study demonstrates accurate physicochemical property, exposure, and cytotoxicity information on engineered nanoparticles in food, which is a prerequisite for the successful safety assessment of nanofood products.

Complex magnetic field exposure system for in vitro experiments at intermediate frequencies

In occupational environments, an increasing number of electromagnetic sources emitting complex magnetic field waveforms in the range of intermediate frequencies is present, requiring an accurate exposure risk assessment with both in vitro and in vivo experiments. In this article, an in vitro exposure system able to generate complex magnetic flux density B-fields, reproducing signals from actual intermediate frequency sources such as magnetic resonance imaging (MRI) scanners, for instance, is developed and validated. The system consists of a magnetic field generation system and an exposure apparatus realized with a couple of square coils. A wide homogeneity (99.9%) volume of 210 × 210 × 110 mm(3) was obtained within the coils, with the possibility of simultaneous exposure of a large number of standard Petri dishes. The system is able to process any numerical input sequence through a filtering technique aimed at compensating the coils' impedance effect. The B-field, measured in proximity to a 1.5 T MRI bore during a typical examination, was excellently reproduced (cross-correlation index of 0.99). Thus, it confirms the ability of the proposed setup to accurately simulate complex waveforms in the intermediate frequency band. Suitable field levels were also attained. Moreover, a dosimetry index based on the weighted-peak method was evaluated considering the induced E-field on a Petri dish exposed to the reproduced complex B-field. The weighted-peak index was equal to 0.028 for the induced E-field, indicating an exposure level compliant with the basic restrictions of the International Commission on Non-Ionizing Radiation Protection. Bioelectromagnetics 34:211-219, 2013. © 2012 Wiley Periodicals, Inc.

Searching for global descriptors of engineered nanomaterial fate and transport in the environment.

Engineered nanomaterials (ENMs) are a new class of environmental pollutants. Researchers are beginning to debate whether new modeling paradigms and experimental tests to obtain model parameters are required for ENMs or if approaches for existing pollutants are robust enough to predict ENM distribution between environmental compartments. This Account outlines how experimental research can yield quantitative data for use in ENM fate and exposure models. We first review experimental testing approaches that are employed with ENMs. Then we compare and contrast ENMs against other pollutants. Finally, we summarize the findings and identify research needs that may yield global descriptors for ENMs that are suitable for use in fate and transport modeling. Over the past decade, researchers have made significant progress in understanding factors that influence the fate and transport of ENMs. In some cases, researchers have developed approaches toward global descriptor models (experimental, conceptual, and quantitative). We suggest the following global descriptors for ENMs: octanol-water partition coefficients, solid-water partition coefficients, attachment coefficients, and rate constants describing reactions such as dissolution, sedimentation, and degradation. ENMs appear to accumulate at the octanol-water interface and readily interact with other interfaces, such as lipid-water interfaces. Batch experiments to investigate factors that influence retention of ENMs on solid phases are very promising. However, ENMs probably do not behave in the same way as dissolved chemicals, and therefore, researchers need to use measurement techniques and concepts more commonly associated with colloids. Despite several years of research with ENMs in column studies, available summaries tend to discuss the effects of ionic strength, pH, organic matter, ENM type, packing media, or other parameters qualitatively rather than reporting quantitative values, such as attachment efficiencies, that would facilitate comparison across studies. Only a few structure-activity relationships have been developed for ENMs so far, but such evaluations will facilitate the understanding of the reactivities of different forms of a single ENM. The establishment of predictive capabilities for ENMs in the environment would enable accurate exposure assessments that would assist in ENM risk management. Such information is also critical for understanding the ultimate disposition of ENMs and may provide a framework for improved engineering of nanomaterials that are more environmentally benign.

Advancing risk assessment for emerging infectious diseases for blood and blood products: proceedings of a public workshop

from infectedblooddonorsintheUnitedStatesdemonstrate the need to improve and expedite current approaches for identifying donors at risk for emerging infectious diseases (EIDs). The safety of the US blood supply relies on accurate and timely data on risk factors, data evaluation, identifying potentially at-risk donors, and implementing appropriate interventions to reduce risk. Quantitative risk assessment (QRA) evaluates the risks and benefits of candidate blood safety interventions and relies on rapid data collection of donor risks. However, such data currently take several months to a year or more to collect, creating delays for responding to urgent public health threats. During the 2009 H1N1 influenza pandemic, the Centers for Disease Control and Prevention (CDC) emphasized the importance of temporarily deferring blood and plasma donors experiencing flu symptoms or not in good health at the time of donation. 5 More specific and sensitive screening methods rely on accurate donor exposure data.

Pesticide exposure as a risk factor for amyotrophic lateral sclerosis: A meta-analysis of epidemiological studies: Pesticide exposure as a risk factor for ALS

BackgroundExposure to pesticides and agricultural chemicals has been linked to amyotrophic lateral sclerosis (ALS) although findings have been inconsistent. A meta-analysis of studies published through May, 2011 was conducted to investigate the association of pesticide exposure and risk of ALS. MethodsSix peer-reviewed studies that met criteria were included in a meta-analysis of men involving 1,517 ALS deaths from one retrospective cohort study and 589 ALS or motor neuron disease cases from five case-control studies. A random effects model was used to calculate sex-specific pooled odds ratios (ORs). ResultsEvidence was found for an association of exposure to pesticides and risk of ALS in male cases compared to controls (OR=1.88, 95% CI: 1.36–2.61), although the chemical or class of pesticide was not specified by the majority of studies. ConclusionThis meta-analysis supports the relationship of exposure to pesticides and development of ALS among male cases compared to controls. The weight of evidence links pesticide exposure to ALS; however, additional prospective studies with a target exposure group are necessary to better elucidate the relationship. Future research should focus on more accurate exposure assessment and the use of job exposure matrices.

고엽제 노출에 따른 건강위해의 보건학적 고찰

Objectives: Controversy regarding the relationship between exposure to Agent Orange and disease has progressed for more than four decades, both at home and abroad. Recently, the allegation by US veteran Steve House of the burial of Agent Orange at the US Army base Camp Carroll located in Waegwan-eup, Korea, has emerged. We reviewed published articles and reports related to Agent Orange. Methods: Articles and reports were collected online using the keywords ‘agent orange’ and ‘health’ and then reviewed. Results: A number of epidemiologic studies have reported disease outcomes due to exposure to Agent Orange, while others were unable to establish a link to the injuries of veterans of the Vietnam War. This can be explained by the fact that accurate exposure assessment should be carried out since exposure misclassification in epidemiologic studies can affect estimates of risk. In the case of the burial of Agent Orange at Camp Carroll, an exposure pathway could be through underground water supplies, which differs from the cases of Vietnam and Seveso in Italy. Conclusion: There still remains a dispute among academics regarding the relationship between exposure to Agent Orange and disease, although Agent Orange is a highly toxic chemical. This dispute indicates that accurate exposure pathway and exposure assessment is needed.