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PubMed2004

Variability of environmental exposures to volatile organic compounds.

Although studies of occupational exposure to volatile organic compounds (VOCs) often partition variability across groups, and between and within persons, those of environmental exposure to VOCs have not involved such partitioning. Using data from the Environmental Protection Agency's total exposure assessment methodology (TEAM) studies, we partitioned exposure variability across cities, and between and within persons for nine VOCs. The estimated variance components decreased in the order: within-person > between-person > across city. Despite their smaller magnitudes, estimates of between-person and across-city variance components were sufficiently large to provide reasonable contrast for informative epidemiology studies of most VOCs. Estimates of between-person variance components for environmental VOCs were similar to those published for occupational VOCs (groups defined by job and factory). However, estimates of within-person variance components were much greater for environmental VOCs, probably due to the greater diversity of locations (including the workplace) visited by the general public over time. For benzene and perchloroethylene, we used a simple model to calculate numbers of personal measurements required to relate the exposure level to health outcome statistically. About 10 times more personal measurements would be required to investigate perchloroethylene exposure as compared to benzene exposure; this disparity reflects the greater within-subject variability of perchloroethylene data compared to benzene data. We conclude that variability should be partitioned for environmental VOC exposures in much the same manner as for occupational exposures. There should be sufficient variability in the levels of most VOCs across cities and between subjects to provide reasonable contrast for informative epidemiology studies, as we illustrate for exposures to benzene. Yet, epidemiologists should be wary of investigating environmental VOCs without preliminary data with which to estimate the variance structure of exposure variables.

Air Pollutants↗
PubMed2006

Genetic parameters for canalisation analysis of litter size and litter weight traits at birth in mice.

The aim of this research was to explore the genetic parameters associated with environmental variability for litter size (LS), litter weight (LW) and mean individual birth weight (IW) in mice before canalisation. The analyses were conducted on an experimental mice population designed to reduce environmental variability for LS. The analysed database included 1,976 records for LW and IW and 4,129 records for LS. The total number of individuals included in the analysed pedigree was 3,997. Heritabilities estimated for the traits under an initial exploratory approach varied from 0.099 to 0.101 for LS, from 0.112 to 0.148 for LW and from 0.028 to 0.033 for IW. The means of the posterior distribution of the heritability under a Bayesian approach were the following: 0.10 (LS), 0.13 (LW) and 0.03 (IW). In general, the heritabilities estimated under the initial exploratory approach for the environmental variability of the analysed traits were low. Genetic correlations estimated between the trait and its variability reached values of -0.929 (LS), -0.815 (LW) and 0.969 (IW). The results presented here for the first time in mice may suggest a genetic basis for variability of the evaluated traits, thus opening the possibility to be implemented in selection schemes.

Analysis of Variance↗
PubMed2004

Microbial community dynamics based on 16S rRNA gene profiles in a Pacific Northwest estuary and its tributaries.

We analyzed bacterioplankton community structure in Tillamook Bay, Oregon and its tributaries to evaluate phylogenetic variability and its relation to changes in environmental conditions along an estuarine gradient. Using eubacterial primers, we amplified 16S rRNA genes from environmental DNA and analyzed the PCR products by length heterogeneity polymerase chain reaction (LH-PCR), which discriminates products based on naturally occurring length differences. Analysis of LH-PCR profiles by multivariate ordination methods revealed differences in community composition along the estuarine gradient that were correlated with changes in environmental variables. Microbial community differences were also detected among different rivers. Using partial 16S rRNA sequences, we identified members of dominant or unique gene fragment size classes distributed along the estuarine gradient. Gammaproteobacteria and Betaproteobacteria and members of the Bacteroidetes dominated in freshwater samples, while Alphaproteobacteria, Cyanobacteria and chloroplast genes dominated in marine samples. Changes in the microbial communities correlated most strongly with salinity and dissolved silicon, but were also strongly correlated with precipitation. We also identified specific gene fragments that were correlated with inorganic nutrients. Our data suggest that there is a significant and predictable change in microbial species composition along an estuarine gradient, shifting from a more complex community structure in freshwater habitats to a community more typical of open ocean samples in the marine-influenced sites. We also demonstrate the resolution and power of LH-PCR and multivariate analyses to provide a rapid assessment of major community shifts, and show how these shifts correlate with environmental variables.

Bacteria↗
PubMed2004

Environmental influences on safer sex in young gay men: a situational presentation approach to measuring influences on sexual health.

Environmental influences on sexual behavior are difficult to examine given their temporal distance from the sexual act and the cost of long-term longitudinal studies. We examined environmental influences on risky sexual behavior in young gay men using the Situational Presentation (Sitpres) methodology, where situations in which relevant environmental variables are presented as computer vignettes with the variables randomly allocated, and participants rate the likelihood of their engaging in unsafe sexual behavior. A total of 100 gay men aged between 18 and 26 years of age completed 20 situational presentations with the outcome being the likelihood of engaging in unprotected anal intercourse. On regression analysis, 3 environmental variables significantly predicted safer sex: perceived gay/bisexual men's norms toward condom use; availability of HIV prevention messages; and what one's religion says about gay sex. Not significant were family, media, legal, and work/school attitudes to homosexuality. Demographic variables that were predictors included education, age, sexual orientation, and degree of being "out" about sexual orientation. These data suggest that environmental factors can be approximated using the Sitpres methodology, and that more proximal environmental variables have a stronger impact than distal ones.

Adult↗
PubMed2003

Patterning and predicting aquatic macroinvertebrate diversities using artificial neural network.

A counterpropagation neural network (CPN) was applied to predict species richness (SR) and Shannon diversity index (SH) of benthic macroinvertebrate communities using 34 environmental variables. The data were collected at 664 sites at 23 different water types such as springs, streams, rivers, canals, ditches, lakes, and pools in The Netherlands. By training the CPN, the sampling sites were classified into five groups and the classification was mainly related to pollution status and habitat type of the sampling sites. By visualizing environmental variables and diversity indices on the map of the trained model, the relationships between variables were evaluated. The trained CPN serves as a 'look-up table' for finding the corresponding values between environmental variables and community indices. The output of the model fitted SH and SR well showing a high accuracy of the prediction (r>0.90 and 0.67 for learning and testing process, respectively) for both SH and SR. Finally, the results of this study, which uses the capability of the CPN for patterning and predicting ecological data, suggest that the CPN can be effectively used as a tool for assessing ecological status and predicting water quality of target ecosystems.

Animals↗
PubMed2003

Two studies examining environmental predictors of heavy drinking by college students.

Two sequential studies are presented that examine the validity of a set of environmental variables to predict heavy drinking at college students' most recent drinking occasions. Random telephone interviews (n=1609, n=400) of graduate and undergraduate students attending two large public universities in the southwestern United States were conducted during three separate surveys in 2000 and 2001. An original interview schedule was used and it included measures that examined environmental characteristics of students' most recent drinking events, motivations for drinking, demographics, and alcohol consumption. Using nonparametric exploratory and confirmatory discriminant analyses to distinguish between heavy episodic and non-heavy episodic drinking events, a discriminant function was identified that included the following environmental variables: (1) having many people intoxicated at an event, (2) having illicit drugs available at an event, (3) BYOB events and, (4) the playing of drinking games at the event. The validity of these environmental variables to predict heavy drinking among students was supported in a subsequent study examining a separate sample from the same student population. Environmental factors can be useful to predict heavy drinking events experienced by students. Prevention programs would benefit from targeting such factors in combination with more traditional individual-level approaches.

Adolescent↗
PubMed2006

Environmental effects on pregnancy rate in beef cattle.

Ten years of calving records were examined from Bos taurus crossbred cows (mean of 182 cows/yr) to quantify the effects of environmental conditions during the breeding season on pregnancy rate. Estimated breeding dates were determined by subtracting 283 d from the calving date. Relationships were determined between the proportion of cows bred during the periods from the beginning of the breeding season until d 21, 42, and 60 of the breeding season and the corresponding environmental variables. Weather data were compiled from a weather station located approximately 20 km from the research site. Average daily temperature and relative humidity were used to calculate daily temperature-humidity index (THI). Daily averages for each environmental variable were averaged for each period. Minimum temperature (MNTP) and THI for the first 21 and 42 d of the breeding season were negatively associated (P < 0.001) with pregnancy rate. For the 0-to 21-d, 0- to 42-d, and 0- to 60-d breeding periods, respective r2 for average temperatures were 0.32, 0.37, and 0.11, whereas r2 for MNTP were 0.45, 0.40, and 0.10 and r2 for THI were 0.38, 0.41, and 0.11, respectively, for the same breeding periods. The negative associations of temperature and THI with pregnancy rate are most pronounced during the first 21 d of the breeding season, with a -3.79 and -2.06% change in pregnancy rate for each unit of change in MNTP and THI, respectively. A combination of environmental variables increased the R2 to 0.67. In this analysis, windspeed was found to be positively associated with pregnancy rate in all equations and increased the R2 in all breeding periods. Optimum MNTP for the 0- to 21-d, 0- to 42-d, and 0- to 60-d breeding periods was 12.6, 13.5, and 14.9 degrees C, respectively. For the 0- to 60-d breeding period, optimum THI was 68.0, whereas the THI threshold, the calculated level at which cattle will adapt, was found to be 72.9. Reductions in pregnancy rate are likely when the average MNTP and THI equal or exceed 16.7 degrees C and 72.9, respectively, and for Bos taurus beef cows that are pasture bred during a 60-d spring-summer period.

Animals↗
PubMed2005

Macroinvertebrate community structure in agricultural streams: impact of runoff-related pesticide contamination.

This study aims to assess the runoff-related pesticide contamination, among other environmental factors, that contributes to differentiation in the macroinvertebrate communities inhabiting six streams in northern Germany (Braunschweig, Lower Saxony). A total of 91 macroinvertebrate taxa were sampled three times (April, May and June 2000) during the main period of pesticide application to cereals and sugar beets in the catchment. Thirteen environmental variables (e.g., nutrients, discharge, in-stream structure), including runoff-related pesticide concentrations expressed as a sum parameter based on toxicity units (TU(SUM)), were analyzed using canonical correspondence analysis (CCA) and redundancy analysis. CCA based on species-level data and environmental variables explained 48% of the variance, with TU(SUM), stream width, percentage of detritus in the stream bed, and temperature being the most important variables. The sampling dates were of minor importance for the classification. The community composition in three streams exposed to maximum total pesticide levels between 0.2 x and 0.01 x acute toxicity to Daphnia (48-h LC(50)) was clearly distinct from that at three control sites. Redundancy analysis using average values of the environmental variables and taxonomic orders explained 95% of the variance, with TU(SUM) being the only significant variable. The results show that the present pesticide levels affect the invertebrate community structure in the field. Furthermore, they underline the potential for effects in the field at pesticide concentrations greater than 0.01 x acute toxicity to Daphnia and are thus in agreement with the assumptions underlying the standards set by the European Union uniform principle.

Agriculture↗
PubMed2005

Effects of pH, salt, and macromolecular crowding on the stability of FK506-binding protein: an integrated experimental and theoretical study.

Environmental variables can exert significant influences on the folding stability of a protein, and elucidating these influences provides insight on the determinants of protein stability. Here, experimental data on the stability of FKBP12 are reported for the effects of three environmental variables: pH, salt, and macromolecular crowding. In the pH range of 5-9, contribution to the pH dependence of the unfolding free energy from residual charge-charge interactions in the unfolded state was found to be negligible. The negligible contribution was attributed to the lack of sequentially nearest neighboring charged residues around groups that titrate in the pH range. KCl lowered the stability of FKBP12 and the E31Q/D32N double mutant at small salt concentrations but raised stability after approximately 0.5 M salt. Such a turnover behavior was accounted for by the balance of two opposing types of protein-salt interactions: the Debye-Hückel type, modeling the response of the ions to protein charges, favors the unfolded state while the Kirkwood type, accounting for the disadvantage of the ions moving toward the low-dielectric protein cavity from the bulk solvent, disfavors the unfolded state. Ficoll 70 as a crowding agent was found to have a modest effect on protein stability, in qualitative agreement with a simple model suggesting that the folded and unfolded states are nearly equally adversely affected by macromolecular crowding. For any environmental variable, it is the balance of its effects on the folded and unfolded states that determines the outcome on the folding stability.

Ficoll↗
PubMed1991

Environmental versus analytical variability in exposure measurements.

Measurements of 8-hr time-weighted average (TWA) exposures are subject to environmental variability and collection and analytical error. Environmental variability can be represented by the geometric standard deviation (GSD) of the lognormally distributed 8-hr TWAs; analytical variability can be represented by the coefficient of variation (CV) of the normally distributed collection and analytical errors. A mathematical expression is derived for the variance of the measured 8-hr TWAs as a function of the GSD of the true daily average exposures and the total CV of the industrial hygiene method used in monitoring. For typical values of the GSD and CV, environmental variability is far more important than analytical variability in determining the variance of the measured 8-hr TWAs. A resulting policy implication is that the Occupational Safety and Health Administration inappropriately focuses on analytical variability when determining compliance with its permissible exposure limits.

Bias↗
PubMed2006

Determinants of fruit and vegetable intake among 11-year-old schoolchildren in a country of traditionally low fruit and vegetable consumption.

BACKGROUND: Fruit and vegetable consumption is traditionally low in Iceland. The results of the Pro Children cross-Europe survey showed that the consumption was lowest among children in Iceland. The aim of this study was to identify determinants of fruit and vegetable intake among 11-year-old schoolchildren in Iceland. METHODS: A cross-sectional survey was performed in Iceland in the autumn of 2003 as a part of the Pro Children cross-Europe survey. The survey was designed to provide information on actual consumption levels of vegetables and fruits by 11-year-old school children and to assess potential determinants of consumption patterns. A total of 1235 Icelandic children (89%) from 32 randomly chosen schools participated. Hierarchical regression analyses were performed to determine the explained variance of the children's fruit and vegetable intake. In these analyses socio-demographic background variables were entered as a first block, perceived physical-environmental variables as a second block, perceived socio-environmental variables as a third block and personal variables as a fourth block. RESULTS: 64% of the children ate fruit less than once a day, and 61% ate vegetables less than once a day. Respectively, 31% and 39% of the variance in children's fruit and vegetable intake was explained by the determinants studied. About 7% and 13% of the variance in fruit and vegetable intake was explained by the perceived physical-environmental determinants, mainly by availability at home. About 18% and 16% of the variance in fruit and vegetable intake was explained by the personal determinants. For both fruit and vegetable intake, the significant personal determinants were preferences, liking, knowledge of recommendations and self-efficacy. CONCLUSION: Interventions to increase fruit and vegetable intake among children should aim at both environmental factors such as greater availability of fruit and vegetables, and personal factors as self-efficacy and knowledge levels concerning nutrition.

Journal Article↗
PubMed1990

Entrainment of bimodal circatidal rhythms in the shore crab Carcinus maenas.

Individuals of the shore crab Carcinus maenas were exposed to artificial cycles, applied in tidal antiphase, of pairs of the three major environmental variables that entrain circatidal rhythmicity in this species: salinity, temperature, and hydrostatic pressure. During entrainment, the observed locomotor activity patterns were dominated by exogenous responses to high pressure, low temperature, or low salinity. In subsequent constant conditions, many of the crabs showed bimodal circatidal rhythms, with peaks phased to the times of expected high-tide characteristics of high pressure, low temperature, or high salinity. Similar bimodal rhythms were induced by exposing freshly captured crabs, with free-running circatidal rhythms, to tidal antiphase cycles of each of the three environmental variables applied individually. The hypothesis that circatidal rhythmicity in this species is controlled by at least two separate circatidal oscillators, with differential sensitivities to specific cyclical environmental variables, is discussed.

Animals↗
PubMed2004

Environmental factors influencing microcystin distribution and concentration in the Midwestern United States.

During May-September 2000-2001, physicochemical data were collected from 241 lakes in Missouri, Iowa, northeastern Kansas, and southern Minnesota U.S.A., to determine the environmental variables associated with high concentrations of the cyanobacterial hepatotoxin microcystin (MC). The study region represents a south-north latitudinal gradient in increasing trophic status, with total phosphorus (TP) and total nitrogen (TN) values ranging between 2-995 and 90-15870 microg/L, respectively. Particulate MC values, measured by ELISA, ranged from undetectable to 4500 ng/L and increased with increasing latitude. Despite latitudinal trends, environmental variables explained < 50% of the variation in MC values. Inspection of MC-TN and MC-Secchi bivariate plots revealed distinctly nonlinear trends, suggesting optima for maximum MC values. Nonlinear interval maxima regression indicated that MC-TN maxima were characterized by a unimodal curve, with maximal (> 2000 ng/L) MC values occurring between 1500 and 4000 microg/L TN. Above 8000 microg/L TN all MC values were < 150 ng/L. MC-Secchi maxima were characterized by exponential decline, with maximal MC values occurring at Secchi depths < 2.5 m. The development of empirical relationships between environmental variables and MC values is critical to effective lake management and minimization of human health risks associated with the toxin. This study indicates MC values are linked to the physicochemical environment; however, the relationships are not traditional linear models.

Carcinogens↗
PubMed1999

Effects of environmental factors on child survival in Bangladesh: a case control study.

The need for further studies on relationships between deaths and environmental variables has been reported in the literature. This case-control study was, therefore, carried out to find out the associations between several social and environmental variables and deaths of children due to infectious diseases such as those leading to diarrhoea, acute respiratory infection, measles and other diseases. Six hundred and twenty-five deaths (cases) and an equal number of matched living children (controls) aged 1-59 months, were studied in rural Matlab. An analysis of crude and adjusted odds ratio showed differential associations. Sources of drinking water, amount of stored water, conditions of latrines, number of persons sleeping with the child and the type of cooking site were statistically significantly associated with deaths due to infectious diseases after controlling for breast feeding, immunization, and the family size. Significant associations were also observed between: (i) the sources of drinking water and deaths due to ARI, and (ii) conditions of latrines and deaths due to diarrhoeal diseases, after controlling for the confounding variables. Several other environmental factors also showed associations with these various death groups, but they were not statistically significant. The size of the samples in death groups (small) and the prevalence of more or less homogeneous environmental health conditions probably diminished the magnitude of the effects. The results of the study reconfirm the importance of environmental health intervention in child survival, irrespective of breast-feeding, immunization, and selected social variables.

Bangladesh↗
PubMed2004

Integral strategy for evaluation of fecal indicator performance in bird-influenced saline inland waters.

Wild birds are an important nonpoint source of fecal contamination of surface waters, but their contribution to fecal pollution is mostly difficult to estimate. Thus, to evaluate the relation between feces production and input of fecal indicator bacteria (FIB) into aquatic environments by wild waterfowl, we introduced a new holistic approach for evaluating the performance of FIB in six shallow saline habitats. For this, we monitored bird abundance, fecal pellet production, and the abundance of FIB concomitantly with a set of environmental variables over a 9-month period. For estimating fecal pellet production, a new protocol of fecal pellet counting was introduced, which was called fecal taxation (FTX). We could show that, over the whole range of investigated habitats, bird abundance, FTX values, and FIB abundance were highly significantly correlated and could demonstrate the good applicability of the FTX as a meaningful surrogate parameter for recent bird abundances and fecal contamination by birds in shallow aquatic ecosystems. Presumptive enterococci (ENT) were an excellent surrogate parameter of recent fecal contamination in these saline environments for samples collected at biweekly to monthly sampling intervals while presumptive Escherichia coli and fecal coliforms (FC) were often undetectable. Significant negative correlations with salinity indicated that E. coli and FC survival was hampered by osmotic stress. Statistical analyses further revealed that fecal pollution-associated parameters represented one system component independent from other environmental variables and that, besides feces production, rainfall, total suspended solids (direct), and trophy (indirect) had significant positive effects on ENT concentrations. Our holistic approach of linking bird abundance, feces production, and FIB detection with environmental variables may serve as a powerful model for application to other aquatic ecosystems.

Animals↗
PubMed1984

An environmental and demographic analysis of otitis media in rural Australian aborigines.

Otitis media (OM) and tympanic scarring prevalence among rural Australian Aboriginal children is examined in relation to age, sex, community size and 34 environmental variables pertaining to living conditions and climate. The environmental variables are reduced to a smaller set of underlying factors via Principal Components Analysis. With age and sex standardized, a multivariate analysis is performed. OM prevalence is profoundly age-dependent, and is related negatively to community socioeconomic status and the presence of swimming facilities. Scarring prevalence is shown to be subject to substantial inter-observer variation, and with the appropriate adjustment manifests an inverse relationship with winter warmth. The data were collected under the National Trachoma and Eye Health Program.

Adolescent↗
PubMed1988

Water supply, sanitation and housing in relation to the risk of infant mortality from diarrhoea.

In a population-based case-control study in the metropolitan areas of Porto Alegre and Pelotas in southern Brazil children dying in infancy from diarrhoea were compared to neighbourhood controls in terms of several social and environmental variables. Factors found to be significantly associated with an increased risk of death from diarrhoea included the non-availability of piped water, the absence of a flush toilet, residence in a poorly built house and household overcrowding. When adjustment was made for confounding variables and the mutual confounding effect of the environmental variables on each other, the only association that remained statistically significant was that with the availability of piped water. The association with poor housing was almost significant (p = 0.052). Compared to those with water piped to their house, those without easy access to piped water were found to be 4.8 times more likely to suffer infant death from diarrhoea (95% confidence interval 1.7 to 13.8) and those with water piped to their plot but not to their house had a 1.5 times greater risk (95% confidence interval 0.8 to 3.0).

Brazil↗
PubMed2006

Spatiotemporal variability of stream habitat and movement of three species of fish.

Relationships between environmental variability and movement are poorly understood, due to both their complexity and the limited ecological scope of most movement studies. We studied movements of fantail (Etheostoma flabellare), riverweed (E. podostemone), and Roanoke darters (Percina roanoka) through two stream systems during two summers. We then related movement to variability in measured habitat attributes using logistic regression and exploratory data plots. We indexed habitat conditions at both microhabitat (i.e., patches of uniform depth, velocity, and substrate) and mesohabitat (i.e., riffle and pool channel units) spatial scales, and determined how local habitat conditions were affected by landscape spatial (i.e., longitudinal position, land use) and temporal contexts. Most spatial variability in habitat conditions and fish movement was unexplained by a site's location on the landscape. Exceptions were microhabitat diversity, which was greater in the less-disturbed watershed, and riffle isolation and predator density in pools, which were greater at more-downstream sites. Habitat conditions and movement also exhibited only minor temporal variability, but the relative influences of habitat attributes on movement were quite variable over time. During the first year, movements of fantail and riverweed darters were triggered predominantly by loss of shallow microhabitats; whereas, during the second year, microhabitat diversity was more strongly related (though in opposite directions) to movement of these two species. Roanoke darters did not move in response to microhabitat-scale variables, presumably because of the species' preference for deeper microhabitats that changed little over time. Conversely, movement of all species appeared to be constrained by riffle isolation and predator density in pools, two mesohabitat-scale attributes. Relationships between environmental variability and movement depended on both the spatiotemporal scale of consideration and the ecology of the species. Future studies that integrate across scales, taxa, and life-histories are likely to provide greater insight into movement ecology than will traditional, single-season, single-species approaches.

Animals↗