Comprehensive skeletal phenotyping and linkage mapping in an intercross of recombinant congenic mouse strains HcB-8 and HcB-23.

Bone biomechanical performance is a complex trait or, more properly, an ensemble of complex traits. Biomechanical performance incorporates flexibility under loading, yield and failure load, and energy to failure; all are important measures of bone function. To date, the vast majority of work has focused on yield and failure load and its surrogate, bone mineral density. We performed a reciprocal intercross of the mouse strains HcB-8 and HcB-23 to map and ultimately identify genes that contribute to differences in biomechanical performance. Mechanical testing was performed by 3-point bending of the femora. We measured femoral diaphysis cross-sectional anatomy from photographs of the fracture surfaces. We used beam equations to calculate material level mechanical properties. We performed a principal component (PC) analysis of normalized whole bone phenotypes (17 input traits). We measured distances separating mandibular landmarks from calibrated digital photographs and performed linkage analysis. Experiment-wide α = 0.05 significance thresholds were established by permutation testing. Three quantitative trait loci (QTLs) identified in these studies illustrate the advantages of the comprehensive phenotyping approach. A pleiotropic QTL on chromosome 4 affected multiple whole bone phenotypes with LOD scores as large as 17.5, encompassing size, cross-sectional ellipticity, stiffness, yield and failure load, and bone mineral density. This locus was linked to 3 of the PCs but unlinked to any of the tissue level phenotypes. From this pattern, we infer that the QTL operates by modulating the proliferative response to mechanical loading. On this basis, we successfully predicted that this locus also affects the length of a specific region of the mandible. A pleiotropic locus on chromosome 10 with LOD scores displays opposite effects on failure load and toughness with LOD scores of 4.5 and 5.5, respectively, so that the allele that increases failure load decreases toughness. A chromosome 19 QTL for PC2 with an LOD score of 4.8 was not detected with either the whole bone or tissue level phenotypes. We conclude that first, comprehensive, system-oriented phenotyping provides much information that could not be obtained by focusing on bone mineral density alone. Second, mechanical performance includes inherent trade-offs between strength and brittleness. Third, considering the aggregate phenotypic data allows prediction of novel QTLs.

Personal exposure to particulate PAHs and anthraquinone and oxidative DNA damages in humans.

Recent studies suggest that DNA oxidative damage be related to the chemical constituents of ambient particles. The purpose of this study was to examine whether particulate polycyclic aromatic hydrocarbons (PAHs) and quinone-structure chemicals increase body burden of oxidative stress in human exposed to heavy traffic volume. We recruited two nonsmoking security guards who worked at a university campus gate near a heavily trafficked road. Each subject wore a personal air sampler for 24h per day to estimate exposures to 24 PAHs and anthraquinone (AnQ) in PM(2.5). Daily pre- and post-work shift spot urines were collected for 29d from each subject. Urine samples were analyzed for 8-hydroxy-2'-deoxyguanosine (8-OHdG). Additionally, using 19 organic tracers other than 24 PAHs and AnQ, a receptor source apportionment model of chemical mass balance was applied to determine the contributions of sources on the PM: gasoline vehicle, diesel vehicle, coal burning, vegetable debris, cooking, natural gas and biomass burning. The relationship among urinary 8-OHdG, individual PAH, and AnQ was demonstrated as follows: the average urinary concentration of 8-OHdG was increased more than three times after 8-h work-shift than those before the work shift. All the 24 PAH and AnQ levels were positively and significantly associated with the post-work urinary 8-OHdG. The results from source apportionment suggest vehicular emission to be the dominant source of personal exposure to PM(2.5). Our finding indicates that personal air exposures to 24 individual PAHs and AnQ originating from traffic emissions are important in increasing oxidative burdens in human body.

PM2.5 constituents and oxidative DNA damage in humans.

Previous studies suggested that certain constituents of ambient PM2.5 can induce or increase oxidative stress in biological systems. The present study is designed to examine whether exposure to traffic generated particles increases the burden of oxidative stress in humans and to identify specific PM2.5 constituents responsible for pollution-induced oxidative stress. We recruited two nonsmoking security guards who worked at a university campus gate by a heavily trafficked road. Pre- and post-workshift spot urines were collected on each of the 29 days of measurement. Concentrations of PM2.5 mass and 126 chemical species were measured at the worksite and a campus background site simultaneously. Urine samples were analyzed for 8-hydroxy-2'-deoxyguanosine (8-OHdG). Factor analysis and linear mixed-effects regression models were used in statistical analyses. Three clusters of PM2.5 species were identified, including PAHs, metals, and polar organic compounds. Urinary concentrations of 8-OHdG increased by > 3 times following an eight-hour workshift in participants. Pre-workshift urinary concentrations of 8-OHdG were associated with PM2.5 concentrations at the background site. Post-workshift 8-OHdG concentrations were significantly and positively associated with PM2.5 mass, PAHs, and metals, but not polar organic species, measured at the worksite. Our findings provide direct evidence in humans that PM compositions are important in increasing oxidative stress burdens. Our results support that PAHs and metals are biologically active constituents of PM2.5 with regards to the induction of oxidative DNA damages in the human body.

Health effects of real-world exposure to diesel exhaust in persons with asthma.

Many people, including people with asthma, experience short-term exposure to diesel exhaust (DE*) during daily activities. The health effects of such exposures, however, remain poorly understood. The present study utilized a real-world setting to examine whether short-term DE exposure would (1) worsen asthma symptoms, (2) augment airway inflammation, or (3) increase oxidative stress burdens. The study also examined exposure-response relations for several DE components and the contribution of background asthma severity to individuals' respiratory responses to DE exposure. Sixty people participated in the study; 31 had mild asthma and 29 had moderate asthma. Each participant completed an exposure and a control session. During the exposure session, participants walked for 2 hours along a heavily trafficked city street where motor vehicle access was restricted to buses and official taxicabs. These vehicles were powered by diesel engines. During the control session, participants walked for the same duration and at the same speed in a public park where motor vehicle traffic was prohibited. The concentrations of elemental carbon (EC), NO2, ultrafine particles (UFP), and particulate matter less than or equal to 2.5 microm in aerodynamic diameter (PM2.5) during exposure sessions were, on average, 4.8, 4.0, 3.4, and 2.0 times higher, respectively, than during control sessions. Increases in asthma symptom score and in the daily use of asthma reliever medication within the 7-day measurement period after exposure were not significant. Some effects on lung function were statistically significant. Compared with control sessions, forced expiratory volume in the first second (FEV1) was reduced 3.0% to 4.1%, and forced vital capacity (FVC) was reduced 2.8% to 3.7% in the 5 hours immediately after the exposure sessions. Analyses of biomarkers showed that the exposure sessions led to a significant reduction in exhaled breath condensate (EBC) pH and to significant increases in induced sputum neutrophils and myeloperoxidase (MPO). The changes in lung function indices (FEV1, FVC, and forced expiratory flow during the middle half of the FVC [FEF25-75]) were most consistently associated with UFP and EC exposures, whereas the changes in EBC pH were most consistently associated with NO2 exposure. In addition, NO2 had a significant effect on bronchial reactivity and on the amount of interleukin-8 (IL-8) in induced sputum; it also modified the UFP effect on EBC pH and the EC effect on exhaled nitric oxide (eNO). However, our findings cannot be taken as demonstrating a causal association with any measured pollutant, because the measured pollutant concentrations may simply represent the entire roadside diesel-traffic exposure that comprises not only the pollutants measured in this study but also other pollutants in the complex DE mixture and resuspended coarse particles from road dust, engine debris, and tire debris. The effects of exposure appeared to be larger in the more severe asthmatic group for most outcomes measured. In conclusion, short-term exposure to urban roadside diesel traffic led to consistent and significant reductions in lung function, accompanied by airway acidification and neutrophilic inflammation. Our findings help to explain the epidemiologic evidence on diesel traffic health effects in persons with asthma.

Hazardous chemicals in synthetic turf materials and their bioaccessibility in digestive fluids.

Many synthetic turf fields consist of not only artificial grass but also rubber granules that are used as infill. The public concerns about toxic chemicals possibly contained in either artificial (polyethylene) grass fibers or rubber granules have been escalating but are based on very limited information available to date. The aim of this research was to obtain data that will help assess potential health risks associated with chemical exposure. In this small-scale study, we collected seven samples of rubber granules and one sample of artificial grass fiber from synthetic turf fields at different ages of the fields. We analyzed these samples to determine the contents (maximum concentrations) of polycyclic aromatic hydrocarbons (PAHs) and several metals (Zn, Cr, As, Cd, and Pb). We also analyzed these samples to determine their bioaccessible fractions of PAHs and metals in synthetic digestive fluids including saliva, gastric fluid, and intestinal fluid through a laboratory simulation technique. Our findings include: (1) rubber granules often, especially when the synthetic turf fields were newer, contained PAHs at levels above health-based soil standards. The levels of PAHs generally appear to decline as the field ages. However, the decay trend may be complicated by adding new rubber granules to compensate for the loss of the material. (2) PAHs contained in rubber granules had zero or near-zero bioaccessibility in the synthetic digestive fluids. (3) The zinc contents were found to far exceed the soil limit. (4) Except one sample with a moderate lead content of 53 p.p.m., the other samples had relatively low concentrations of lead (3.12-5.76 p.p.m.), according to soil standards. However, 24.7-44.2% of the lead in the rubber granules was bioaccessible in the synthetic gastric fluid. (5) The artificial grass fiber sample showed a chromium content of 3.93 p.p.m., and 34.6% and 54.0% bioaccessibility of lead in the synthetic gastric and intestinal fluids, respectively.

1-Hydroxypyrene concentrations in first morning voids and 24-h composite urine: intra- and inter-individual comparisons.

Urinary 1-hydroxypyrene (1-OHP) has been suggested as an exposure biomarker for polycyclic aromatic hydrocarbons (PAHs). However, it remains unknown whether a first morning urine sample can be used to reflect average exposure. In this paper, we examine intra-individual differences and inter-individual associations between first morning voids and 24-h composite urine samples. The analysis was performed using data collected from 100 adults who had a wide range of PAH exposure due to differences in their occupation, e.g., coke oven workers vs. non-coke oven workers. For each subject, all the urine voids within each of two 24-h measurement periods were collected. Results showed a significant (40% to 62%) intra-individual difference between first morning voids and 24-h urinary 1-OHP concentrations (in ng/ml urine). Creatinine adjustments of 1-OHP concentrations (in micromol/mol urinary creatinine) reduced the intra-individual difference by approximately 10%. Across all the subjects, a high overall correlation (r=0.76) was observed between first morning and 24-h average 1-OHP concentrations. Work environment and sampling season were found to significantly affect the relationship between first morning and 24-h 1-OHP concentrations. An increase of 1 ng/ml of first morning urinary 1-OHP predicted an increase of 0.5 and 0.25 ng/ml of 24-h urinary 1-OHP for coke oven workers and non-coke oven workers, respectively. Data collected in a winter season showed a higher correlation between first morning and 24-h concentrations than data collected in a fall season. Creatinine adjustments did not significantly improve overall correlations between first morning void and 24-h measurements, but increased total variances for 24-h urines explained by first morning urines in coke workers.

Respiratory effects of exposure to diesel traffic in persons with asthma.

BACKGROUND: Air pollution from road traffic is a serious health hazard, and people with preexisting respiratory disease may be at increased risk. We investigated the effects of short-term exposure to diesel traffic in people with asthma in an urban, roadside environment. METHODS: We recruited 60 adults with either mild or moderate asthma to participate in a randomized, crossover study. Each participant walked for 2 hours along a London street (Oxford Street) and, on a separate occasion, through a nearby park (Hyde Park). We performed detailed real-time exposure, physiological, and immunologic measurements. RESULTS: Participants had significantly higher exposures to fine particles (<2.5 microm in aerodynamic diameter), ultrafine particles, elemental carbon, and nitrogen dioxide on Oxford Street than in Hyde Park. Walking for 2 hours on Oxford Street induced asymptomatic but consistent reductions in the forced expiratory volume in 1 second (FEV1) (up to 6.1%) and forced vital capacity (FVC) (up to 5.4%) that were significantly larger than the reductions in FEV1 and FVC after exposure in Hyde Park (P=0.04 and P=0.01, respectively, for the overall effect of exposure, and P<0.005 at some time points). The effects were greater in subjects with moderate asthma than in those with mild asthma. These changes were accompanied by increases in biomarkers of neutrophilic inflammation (sputum myeloperoxidase, 4.24 ng per milliliter after exposure in Hyde Park vs. 24.5 ng per milliliter after exposure on Oxford Street; P=0.05) and airway acidification (maximum decrease in pH, 0.04% after exposure in Hyde Park and 1.9% after exposure on Oxford Street; P=0.003). The changes were associated most consistently with exposures to ultrafine particles and elemental carbon. CONCLUSIONS: Our observations serve as a demonstration and explanation of the epidemiologic evidence that associates the degree of traffic exposure with lung function in asthma.