Health Impact Evaluation of Boron in Drinking Water: A Geographical Risk Assessment in Northern France

Objective: To evaluate health impact of boron in drinking water. Methods: A regional scale geographical study in Northern France was conducted. Assessment of boron blood levels in a group of 180 healthy individuals and correlation with boron content in drinking water were followed by an assessment of health indicators such as birth rates, mortality rates, and sex ratios in zones of different boron content in drinking water. Results: After necessary adjustments, men living in municipalities with more than 0.30 mg/L of boron in drinking water had elevated but not significant boron blood levels compared with those living in municipalities with boron water levels of less than 0.30 mg/L (159.1 versus 123.0 ng/g; p > 0.05). The standardized birth ratio adjusted for the reference geographic zone and calendar time period was 1.07 and 1.28 in the low and high (>0.3 mg/L) boron content municipalities, respectively. The birth rate in municipalities with high boron content in drinking water was higher than that of the reference geographic zone and of the French general population (p < 10^-4). The standardized mortality ratio adjusted for the reference geographic zone and calendar time period was 0.94 and 0.92 in the low and high boron content municipalities, respectively. The mortality rate in municipalities with high boron content in drinking water was less than that of the reference geographic zone and of the French general population (p < 10^-3). No statistical difference was noted in the male–female sex ratios between the different municipality zones (p = 0.45). Conclusions: The results of this study do not support the idea of a deleterious effect of boron on human health, at the boron water level contents found in this specific region. In fact, there is a tendency toward a beneficial effect with low-dose environmental exposure (less than 1 mg/L of boron) in drinking water.     

The risks of risk-based regulation: insights from the environmental policy domain

Risk-based regulation has become increasingly popular in recent years. Proponents argue that it facilitates robust governance, contributing to efficient and effective use of regulatory resources and delivering interventions in proportion to risk. Critics contend that the challenges of operationalising risk-based governance mitigate its potential benefits. In this paper we start by considering what we mean by risk-based governance and discuss some of the factors shaping the adoption of such strategies. We then consider the development and operation of risk-based approaches in the environmental policy domain, focusing specifically on the regulation of contaminated land and radioactive waste. We argue that whilst risk-based approaches can offer important benefits, they face a range of epistemic, institutional and normative challenges that can play an important role in shaping the way that organisations manage both risks to society and their own institutional risks. This has profound implications for achieving regulatory objectives and, for this paper, the environmental outcomes that the regulations are designed to deliver.     

Land changes and their driving forces in the Southeastern United States

The ecoregions of the Middle Atlantic Coastal Plain, Southeastern Plains, Piedmont, and Blue Ridge provide a continuum of land cover from the Atlantic Ocean to the highest mountains in the East. From 1973 to 2000, each ecoregion had a unique mosaic of land covers and land cover changes. The forests of the Blue Ridge Mountains provided amenity lands. The Piedmont forested area declined, while the developed area increased. The Southeastern Plains became a commercial forest region, and most agricultural lands that changed became forested. Forests in the Middle Atlantic Coastal Plain declined, and development related to recreation and retirement increased. The most important drivers of land conversion were associated with commercial forestry, competition between forest and agriculture, and economic and population growth. These and other drivers were modified by each ecoregion’s unique suitability and land use legacies with the result that the same drivers often produced different land changes in different ecoregions.     

Estimated home ranges can misrepresent habitat relationships on patchy landscapes

Home ranges of animals are generally structured by the selective use of resource-bearing patches that comprise habitat. Based on this concept, home ranges of animals estimated from location data are commonly used to infer habitat relationships. Because home ranges estimated from animal locations are largely continuous in space, the resource-bearing patches selected by an animal from a fragmented distribution of patches would be difficult to discern; unselected patches included in the home range estimate would bias an understanding of important habitat relationships. To evaluate potential for this bias, we generated simulated home ranges based on optimal selection of resource-bearing patches across a series of simulated resource distributions that varied in the spatial continuity of resources. For simulated home ranges where selected patches were spatially disjunct, we included interstitial, unselected cells most likely to be traveled by an animal moving among selected patches. We compared characteristics of the simulated home ranges with and without interstitial patches to evaluate how insights derived from field estimates can differ from actual characteristics of home ranges, depending on patchiness of landscapes. Our results showed that contiguous home range estimates could lead to misleading insights on the quality, size, resource content, and efficiency of home ranges, proportional to the spatial discontinuity of resource-bearing patches. We conclude the potential bias of including unselected, largely irrelevant patches in the field estimates of home ranges of animals can be high, particularly for home range estimators that assume uniform use of space within home range boundaries. Thus, inferences about the habitat relationships that ultimately define an animal's home range can be misleading where animals occupy landscapes with patchily distributed resources.     

Characterizing source-sink dynamics with genetic parentage assignments

Source-sink dynamics have been suggested to characterize the population structure of many species, but the prevalence of source-sink systems in nature is uncertain because of inherent challenges in estimating migration rates among populations. Migration rates are often difficult to estimate directly with demographic methods, and indirect genetic methods are subject to a variety of assumptions that are difficult to meet or to apply to evolutionary timescales. Furthermore, such methods cannot be rigorously applied to high-gene-flow species. Here, we employ genetic parentage assignments in conjunction with demographic simulations to infer the level of immigration into a putative sink population. We use individual-based demographic models to estimate expected distributions of parent-offspring dyads under competing sink and closed-population models. By comparing the actual number of parent-offspring dyads (identified from multilocus genetic profiles) in a random sample of individuals taken from a population to expectations under these two contrasting demographic models, it is possible to estimate the rate of immigration and test hypotheses related to the role of immigration on population processes on an ecological timescale. The difference in the expected number of parent-offspring dyads between the two population models was greatest when immigration into the sink population was high, indicating that unlike traditional population genetic inference models, the highest degree of statistical power is achieved for the approach presented here when migration rates are high. We used the proposed genetic parentage approach to demonstrate that a threatened population of Marbled Murrelets (Braclhyrarmphus marmotus) appears to be supplemented by a low level of immigration (approximately 2-6% annually) from other populations.     

Widespread contribution of methane-cycle bacteria to the diets of lake profundal chironomid larvae

Reports of unexpectedly 13C-depleted chironomid larvae in lakes have led to an hypothesis that significant transfer of detrital organic matter to chironomid larvae may occur via methane-cycle bacteria. However, to date little is known of how such transfer might vary across species and lakes. We gathered data from 87 lakes to determine how widespread this phenomenon might be and to define boundaries for its likely magnitude. Carbon stable isotope values of chironomid larvae varied greatly between taxa. Very marked 13C-depletion was evident only in certain taxa, especially Chironomus plumosus, C. anthracinus, and C. tenuistylus, all characteristic of eutrophic or dystrophic lakes and known to be tolerant of low oxygen conditions. Furthermore, marked 13C-depletion was only found in larvae from lakes in which late-summer hypolimnetic oxygen depletion near the sediment surface was below an apparent threshold concentration of 2-4 mg O2/L. Similarly, application of a two-source mixing model suggested that methanotrophic bacteria made the greatest contribution to profundal chironomid growth (0-70% of larval carbon) when the late-summer oxygen concentration dropped below approximately 2 mg O2/L. Our study demonstrates that methane-derived carbon is an important, but often neglected, contribution to the flux of carbon through the food webs of many productive or dystrophic lakes.     

Influence of fur trade,famine, and forest fires on moose and woodland caribou populations in northwestern Ontario from 1786 to 1911

Hudson’s Bay Company records were used to estimate the 1786–1911 annual number of moose (Alces alces andersonii) and caribou (Rangifer tarandus caribou) involved in trade by northern Ojibwa natives to the company post at Osnaburgh House (51°10′N 90°15′W) in northwest Ontario, Canada. The human population for the early 19th century, and the number and severity of human starvations from 1786 to 1911 were estimated. The extent of forest fires in the region around Osnaburgh was documented using a “fire-day” index computed from Hudson’s Bay Company journals and using qualitative archival information. It is argued that the human population was too small to have caused the observed early 19th century moose and caribou population decline solely through predation. Likewise, severe early 19th century famines were caused by climatic factors rather than by declines in moose and caribou numbers. Habitat change caused by increased forest fires correlates with the observed decline of caribou, while moose increased and subsequently collapsed as winter shelter was destroyed. A burgeoning human population, sustained during winter food shortages on potatoes donated by the Hudson’s Bay Company, then kept ungulate populations to low levels until the late 19th century. Only then did maturing forests and a new outbreak of fires provide renewed habitat for resurgences of, respectively, caribou and moose.     

The use of passive sampling to monitor forest exposure to O3, NO2 and SO2: a review and some case studies

The use of passive sampler systems is reviewed and discussed. These devices are able to determine both spatial and temporal differences in canopy exposure, as is demonstrated by their use in extensive monitoring of air-pollution exposure in forest health plots. Categorising forest health monitoring plots according to air-pollution exposure permits cause-effect analysis of certain forest health responses. In addition, passive sampling may identify areas affected by interaction between different gaseous pollutants. Passive samplers at the stand level can be used to resolve vertical profiles of ozone within the stand, and edge effects, which are important in exposure of understorey and ground flora. Recent case studies using passive samplers to determine forest exposure to gaseous pollutants indicate a potential for the development of spatial models on regional-, landscape-, and stand-level scales and the verification of atmospheric transport models.