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PubMed1987

Integrating uncertainty and interindividual variability in environmental risk assessment.

An integrated, quantitative approach to incorporating both uncertainty and interindividual variability into risk prediction models is described. Individual risk R is treated as a variable distributed in both an uncertainty dimension and a variability dimension, whereas population risk I (the number of additional cases caused by R) is purely uncertain. I is shown to follow a compound Poisson-binomial distribution, which in low-level risk contexts can often be approximated well by a corresponding compound Poisson distribution. The proposed analytic framework is illustrated with an application to cancer risk assessment for a California population exposed to 1,2-dibromo-3-chloropropane from ground water.

California↗
PubMed2005

Environmentally stratified sampling design for the development of Great Lakes environmental indicators.

Understanding the relationship between human disturbance and ecological response is essential to the process of indicator development. For large-scale observational studies, sites should be selected across gradients of anthropogenic stress, but such gradients are often unknown for apopulation of sites prior to site selection. Stress data available from public sources can be used in a geographic information system (GIS) to partially characterize environmental conditions for large geographic areas without visiting the sites. We divided the U.S. Great Lakes coastal region into 762 units consisting of a shoreline reach and drainage-shed and then summarized over 200 environmental variables in seven categories for the units using a GIS. Redundancy within the categories of environmental variables was reduced using principal components analysis. Environmental strata were generated from cluster analysis using principal component scores as input. To protect against site selection bias, sites were selected in random order from clusters. The site selection process allowed us to exclude sites that were inaccessible and was shown to successfully distribute sites across the range of environmental variation in our GIS data. This design has broad applicability when the goal is to develop ecological indicators using observational data from large-scale surveys.

Animals↗
PubMed2005

Demography in an increasingly variable world.

Recent advances in stochastic demography provide unique insights into the probable effects of increasing environmental variability on population dynamics, and these insights can be substantially different compared with those from deterministic models. Stochastic variation in structured population models influences estimates of population growth rate, persistence and resilience, which ultimately can alter community composition, species interactions, distributions and harvesting. Here, we discuss how understanding these demographic consequences of environmental variation will have applications for anticipating changes in populations resulting from anthropogenic activities that affect the variance in vital rates. We also highlight new tools for anticipating the consequences of the magnitude and temporal patterning of environmental variability.

Animals↗
PubMed2005

Maternal and grandmaternal age effects on developmental instability and wing size in parthenogenetic Drosophila mercatorum.

Age is known to have a large effect upon fertility and survival. Here we study the impact of maternal and grandmaternal age on wing size and developmental instability (DI) in offspring using a parthenogenetic strain of Drosophila mercatorum. This enabled us to cancel out any genetic variance between individuals. The mean centroid size of the wings was estimated in offspring from four maternal/grandmaternal age groups. Further, DI was calculated by measuring phenotypic variability and correcting this index for the bias produced by the environmental variability. The offspring developed from eggs laid by mothers belonging to four different age groups with young (Y) or old (O) mothers and grandmothers. The age groups are: YY, YO, OY and OO, with the first letter referring to the age of the grandmother and the second letter to the age of the mother. We consider flies between three to six days of age as young and flies between 15 and 18 days of age as old. We found that environmental variability was present in this study and therefore the correction for its bias on phenotypic variability was shown to be necessary for a correct interpretation of the results. DI displayed, for most of the traits investigated, a significantly higher level in the OY and OO age groups, as compared to the YY and YO age groups. The mean centroid size of the wings were in almost all cases significantly different among the age groups with the highest mean value in the OY group for all traits. This investigation shows that offspring are affected by maternal age and that this effect can be transmitted maternally across more than one generation.

Age Factors↗
PubMed2001

Alzheimer dementia in Down's syndrome: the relevance of cognitive ability.

More years of education have been found to be associated with a lower rate of Alzheimer disease (AD) in individuals without intellectual disability. It has been proposed that education reflects greater 'synaptic reserve' and that greater synaptic reserve may defer the development of AD. The present study compared individuals with Down's syndrome (DS) who were found to have symptoms of dementia with those who remained symptom-free to determine if the two groups differed in their level of education, employment, recreational activities, years in an institution or overall level of cognitive functioning. Thirty-five adults with DS aged between 29 and 67 years were assessed. The participants were recruited from a community health facility and included individuals with a wide range of ability levels. Neuropsychological testing, caregiver report and the Dementia Scale for Down Syndrome (Gedye 1995) were used to identify decline in participants over periods of 6 months to 3 years. After the effect of age was statistically removed, multiple regression analyses revealed that level of cognitive functioning was significantly associated with decline such that a higher level of cognitive functioning predicted less decline. None of the environmental variables (i.e. educational level, years in an institution and employment) were directly associated with decline; however, a post hoc regression using level of cognitive functioning as the outcome variable revealed that level of cognitive functioning itself was associated with these environmental variables. A higher level of cognitive functioning was associated with fewer cases of dementia in individuals with DS, and level of cognitive functioning appears to be associated with environmental factors such as level of education, years in an institution and employment. The present findings suggest that environmental interventions aimed at improving level of cognitive functioning may also be useful in deferring the onset of dementia.

Adult↗
PubMed2006

Mercury bioaccumulation in forage fish communities invaded by rainbow smelt (Osmerus mordax).

We compared total mercury concentrations ([Hg]) among 6 forage fish species in 25 central Canadian lakes and related [Hg] to adjusted-delta15N (an index of trophic position), delta13C, growth rate, and a suite of environmental variables. Growth rates were also compared among species and related to environmental variables. We found that rainbow smelt (Osmerus mordax), a recent invader in many of these lakes, had intermediate [Hg] and growth rates relative to other species. Forage fish growth rates differed significantly among species and were related to latitude (inverse relationship) and lake conductivity (positive relationship). Mercury concentrations also differed significantly among species and the strongest predictors were growth rate and lake conductivity; [Hg] was significantly and negatively related to both. Adjusted-delta15N explained very little variation in [Hg] and was significant only when the analysis was restricted to biotic variables. These results indicate that biomagnification may not be observed at fine scales of trophic differentiation and that rainbow smelt are unlikely to cause post-invasion [Hg] increases in most predatory fish species.

Animals↗
PubMed2005

Methodological scheme for designing the monitoring of genetically modified crops at the regional scale.

According to EC regulations the deliberate release of genetically modified (GM) crops into the agro-environment needs to be accompanied by environmental monitoring to detect potential adverse effects, e.g. unacceptable levels of gene flow from GM to non-GM crops, or adverse effects on single species or species groups thus reducing biodiversity. There is, however, considerable scientific and public debate on how GM crops should be monitored with sufficient accuracy, discussing questions of potential adverse effects, agro-environmental variables or indicators to be monitored and respective detection methods; Another basic component, the appropriate number and location of monitoring sites, is hardly considered. Currently, no consistent GM crop monitoring approach combines these components systematically. This study focuses on and integrates spatial agro-environmental aspects at a landscape level in order to design monitoring networks. Based on examples of environmental variables associated with the cropping of Bt-Maize (Zea maize L.), herbicide-tolerant (HT) winter oilseed rape (Brassica napus L.), HT sugar beet (Beta vulgaris L.), and starch-modified potato (Solanum tuberosum L.), we develop a transferable framework and assessment scheme that comprises anticipated adverse environmental effects, variables to be measured and monitoring methods. These we integrate with a rule-based GIS (geographic information system) analysis, applying widely available spatial area and point information from existing environmental networks. This is used to develop scenarios with optimised regional GM crop monitoring networks.

Beta vulgaris↗
PubMed2000

Patterns of Annual Seed Production by Northern Hemisphere Trees: A Global Perspective.

We tested whether annual seed production (masting or mast fruiting) in Northern Hemisphere trees is an evolved strategy or a consequence of resource tracking by comparing masting patterns with those of annual rainfall and mean summer temperatures, two environmental variables likely to correlate with available resources. There were generally significant negative autocorrelations between the seed crop in year x and year [Formula: see text] (year [Formula: see text] in species of Quercus requiring 2 yr to mature acorns), as expected if resources are depleted in mast years in part by switching resources from growth to reproduction. Spatial autocorrelation in annual seed production generally declined with distance but was statistically significant over large geographic areas. Variability in annual seed production was relatively high and inversely correlated with latitude and generally not bimodally distributed. Patterns of spatial autocorrelation in annual rainfall and summer temperatures are generally similar to those exhibited by annual seed production, and relative variability in annual rainfall is also inversely correlated with latitude. However, these environmental variables exhibit distinctly different patterns of temporal autocorrelation, are much less variable, and are more normally distributed than annual seed production. Combined with the inverse relationship between growth and reproduction previously documented, these results support the hypothesis that variability in annual seed production is an evolved strategy and that annual seed production is more or less normally distributed rather than an all-or-none phenomenon.

mast fruiting↗
PubMed1991

Dietary n-3 (omega-3) polyunsaturated fatty acid effects on animal tumorigenesis.

Environmental variables influence the incidence and expression of disease. Dietary fat is one environmental variable that has been associated experimentally and epidemiologically with alterations in certain types of tumorigenesis. Recently, detailed biochemical analyses have shown that not all fatty acid families possess the same tumor-promoting potential. In general, diets containing high levels of the n-6 polyunsaturated fatty acids have routinely enhanced tumorigenesis in lipid sensitive carcinogen-induced and tumor transplant tumor models, whereas diets with equivalent levels of n-3 polyunsaturated fatty acids have diminished tumorigenesis. At present, there is no definitive biochemical mechanism that fully explains these observations, but several possibilities have been proposed. One of the most attractive of these hypotheses is that each polyunsaturated fatty acid family has an individual effect on eicosanoid metabolism which determines its tumor-promoting potential. Regardless of current uncertainties about mechanisms of action, however, results of numerous animal models affirm the importance of qualitative, as well as quantitative, dietary lipid differences on tumorigenesis. This knowledge strengthens the probability that further advances in our understanding of lipid-tumor interrelationships will have important preventive and therapeutic medical benefits.

Animals↗
PubMed1996

Environmental tobacco smoke exposure and gastroesophageal reflux in infants with apparent life-threatening events.

OBJECTIVE: To study the hypothesis that environmental tobacco smoke exposure in infants diagnosed with an apparent life-threatening event (ALTE) could be a contributing factor to gastroesophageal reflux. METHODS: Thirty-four polygraphic recordings of combined esophageal pH study and respiration in infants with ALTE, age 4.1 +/- 4.9 months, range 0.4-27 months, were studied. This group of children had uncomplicated perinatal history, no congenital anomalies, no neuropathology, and no drug exposure. A written questionnaire was administered to the parents to determine the following: environmental variables, degree of environmental tobacco smoke (ETS) exposure (number of cigarettes/day), and nutrition (breast vs. bottle feeding). RESULTS: There was a strong correlation between pH study parameters and ETS exposure (p < 0.005). The esophageal pH parameters were markedly elevated in the ETS-exposed group and in this group there was a linear relation between the number of cigarettes smoked per day and reflux index, as well as reflux > 5 min/hr (p < 0.05, r = 0.46). Nursing mothers were less likely to be smokers (18.2% vs. 34.0%). The only significant respiratory finding was in the obstructive/mixed apnea group; there was strong association between ETS exposure and high reflux index (p < 0.05). CONCLUSION: We conclude that ETS exposure represents a significant contributing factor to GER. Pediatricians should systematically ask questions about the infant environment, explain the risk of ETS exposure to the caretaker, and recommend that children should remain in a smoke-free environment.

Apnea↗
PubMed2000

Measuring tolerance to herbivory: accuracy and precision of estimates made using natural versus imposed damage.

Tolerance to herbivory (the ability of a plant to incur herbivore damage without a corresponding reduction in fitness) can be measured using either naturally occurring or imposed herbivore damage. After briefly reviewing some of the advantages and disadvantages of these approaches, we present calculations describing the degree to which estimates of tolerance will be biased by environmental variables that affect both herbivory and fitness. With naturally occurring herbivory the presence of environmental variables that are correlated with herbivory and fitness will result in biased estimates of tolerance. In contrast, estimates obtained from experiments in which herbivory is artificially imposed will be unbiased; however, under a wide range of parameter values these estimates will be less precise than estimates obtained from experiments in which herbivory is not manipulated.

Environment↗
PubMed2004

Geographic distribution of environmental factors influencing human skin coloration.

Skin coloration in indigenous peoples is strongly related to levels of ultraviolet radiation (UVR). In this study, the relationships of skin reflectance to seasonal UVR levels and other environmental variables were investigated, with the aim of determining which variables contributed most significantly to skin reflectance. The UVR data recorded by satellite were combined with environmental variables and data on human skin reflectance in a geographic information system (GIS). These were then analyzed visually and statistically through exploratory data analysis, correlation analysis, principal components analysis, least-squares regression analysis, and nonlinear techniques. The main finding of this study was that the evolution of skin reflectance could be almost fully modeled as a linear effect of UVR in the autumn alone. This linear model needs only minor modification, by the introduction of terms for the maximum amount of UVR, and for summer precipitation and winter precipitation, to account for almost all the variation in skin reflectance. A further significant finding was that the effect of summer UVR seems to reach a threshold beyond which further adaptation is difficult.

Environmental Exposure↗
PubMed2001

Intimately linked or hardly speaking? The relationship between genotype and environmental gradients in a Louisiana Iris hybrid population.

Several models of hybrid zone evolution predict the same spatial patterns of genotypic distribution whether or not structuring is due to environment-dependent or -independent selection. In this study, we tested for evidence of environment-dependent selection in an Iris fulva x Iris brevicaulis hybrid population by examining the distribution of genotypes in relation to environmental gradients. We selected 201 Louisiana Iris plants from within a known hybrid population (80 m x 80 m) and placed them in four different genotypic classes (I. fulva, I. fulva-like hybrid, I. brevicaulis-like hybrid and I. brevicaulis) based on seven species-specific random amplified polymorphic DNA (RAPD) markers and two chloroplast DNA haplotypes. Environmental variables were then measured. These variables included percentage cover by tree canopy, elevation from the high water mark, soil pH and percentage soil organic matter. Each variable was sampled for all 201 plants. Canonical discriminant analysis (CDA) was used to infer the environmental factors most strongly associated with the different genotypic groups. Slight differences in elevation (-0.5 m to +0.4 m) were important for distinguishing habitat distributions described by CDA, even though there were no statistical differences between mean elevations alone. I. brevicaulis occurred in a broad range of habitats, while I. fulva had a narrower distribution. Of all the possible combinations, I. fulva-like hybrids and I. brevicaulis-like hybrids occurred in the most distinct habitat types relative to one another. Each hybrid class was not significantly different from its closest parent with regard to habitat occupied, but was statistically unique from its more distant parental species. Within the hybrid genotypes, most, but not all, RAPD loci were individually correlated with environmental variables. This study suggests that, at a very fine spatial scale, environment-dependent selection contributed to the genetic structuring of this hybrid zone.

Altitude↗
PubMed2005

Perceived Neighborhood Environments and physical activity in adolescents.

BACKGROUND: There is a reason to believe that physical environments variables play an especially important role in the level of physical activity. Few studies have examined the association between environmental variables and level of physical activity in adolescents. OBJECTIVES: This study aims were: (1) to evaluate differences in perceived neighborhood environment according to physical activity level and (2) to determine which, if any, perceived neighborhood environmental variables were associated with reported physical activity levels in an adolescent population. METHODS: The sample comprised of 1123 adolescents, which were classified according to physical activity levels into actives (n = 589) and non-active (n = 534). A questionnaire assessed Perceived Neighborhood Environments. Physical activity was assessed by questionnaire and used as the dependent variable. RESULTS: More active children were reported to more significantly (P < 0.05) agree with the importance of the accessibility of shops, the social environment, neighbors with recreational facilities, and aesthetics. Logistic regression analysis showed that aesthetic (OR = 1.302; P = 0.05) and recreational facilities (OR = 1.297; P = 0.05) domains were related to being physically active. CONCLUSIONS: Some perceived neighborhood environmental attributes were found to be associated with level of physical activity in adolescents.

Adolescent↗
PubMed1987

Multivariate analysis of ambient environmental factors and respiratory effects.

Relationships between respiratory health and environmental conditions (pollen, pollution and meteorology) are investigated in 204 subjects in four symptom groups in four geographical clusters in Tucson. Techniques used are principal components, factor and path analysis. Daily respiratory symptoms and peak expiratory flows were recorded during a three-year period. Ambient pollutants, meteorological conditions and pollen types were monitored in or near the clusters. Factor-based scales, which are climate and season specific, are developed for the environmental variables. Three pollutant/meteorological scales represent 'Summer', 'Winter', and 'Humidity'. Four pollen scales represent early and late spring, summer and fall pollen types. Relationships between environmental variables, respiratory symptoms and peak expiratory flow are analyzed with path diagrams, after accounting for age, sex, smoking habits and stove type. The different effects of the environment on asthmatics, allergics and airways obstructive disease subjects have been demonstrated. Many relationships were found between environmental factors and respiratory responses. The pollutant and meteorological variables are related to respiratory symptoms and peak flow directly as well as through interactions with pollen types. Some of the largest positive coefficients are seen in association with seasonal pollen types, specifically, rhinitis and dyspnoea.

Adult↗
PubMed1984

The determinants of actinic skin damage: problems of confounding among environmental and constitutional variables.

Constitutional and environmental determinants of actinic skin damage, assessed by cutaneous microtopography, were evaluated in 1,216 subjects attending the 1981 Busselton Health Survey in Western Australia. Increasing age, male sex, the tendency to burn on exposure to sunlight and outdoor occupation were found to have independent predictive value for the presence of actinic skin damage. Crude positive and inverse associations of actinic skin damage with several other factors were shown to arise from confounding. Effect measures for outdoor leisure pursuits and sunscreen use were underestimated due to inverse associations of these factors with older age, and inverse associations of high-exposure outdoor activities with poor skin response to sunlight. Associations of constitutional traits typical of fair individuals and sunscreen use with the tendency to burn resulted in overestimation of effect measures. Empirical relationships of actinic skin damage with certain leisure activities and with use of sunscreens were also confounded by sex. The results indicate a need for greater attention to confounding in nonexperimental skin cancer research.

Adolescent↗
PubMed1993

Photoperiod, temperature, and regional patterns of conceptions in the USA.

Twenty-two years of monthly values of birth data for the USA, 1967 through 1988, were analyzed by visual inspection. The data were transformed to remove the influence of length of month and of linear trend, and the values were lagged 9 months to approximate the time of conception. Then, 11-year monthly averages were obtained and plotted as standard scores. Thus two 11-year sets of data were independently analyzed, providing the opportunity of replication. Four distinct temporal patterns were found, differing in month of occurrence of the initial trough and peak and the relative sizes of the two troughs; these characteristics of the temporal pattern change systematically with latitude in the eastern and midwestern states. Data from two other continents, the United Kingdom and Australia, also were analyzed using the same method and found to exhibit a temporal pattern during the year similar to the northern states of the USA. Two biologically relevant variables, temperature and photoperiod, were considered as possible controllers and regulators of the annual rhythmicity. Comparisons of the trends in conceptions with these environmental variables, and inspections of the temperatures and photoperiods at which peaks and troughs in conceptions were found, indicated that these environmental variables could not account for the annual rhythmicity in conceptions.

Birth Rate↗
PubMed2004

Effects of pollution on zooplankton abundance and distribution in two estuaries of the Basque coast (Bay of Biscay).

The abundance and spatial distribution of mesozooplankton were compared in the euhaline region of the polluted Bilbao estuary and the unperturbed Urdaibai estuary. The environmental variables measured were salinity, temperature, dissolved oxygen saturation, chlorophyll a, particulate organic matter and Secchi disk depth. Differences in the environmental variables and zooplankton between the estuaries and within the estuaries were tested statistically. Differences in the patterns of mesozooplankton abundance with salinity in each estuary indicated that they were affected by pollution in the Bilbao. Total mesozooplankton, and several mesozooplankton categories were more abundant in the Bilbao at higher salinities but in the Urdaibai at lower salinities. Therefore, we deduced that, in the Bilbao, zooplankton abundance was enhanced by the moderate pollution at the outer euhaline zone and limited by the poorer conditions of the inner zone. The response of the various zooplankton categories to the pollution is discussed.

Animals↗