To assess geographic distributions of elements in the Arctic we compared essential and non-essential elements in the livers of polar bears (Ursus maritimus) collected from five regions within Canada in 2002, in Alaska between 1994 and 1999 and from the northwest and east coasts of Greenland between 1988 and 2000. As, Hg, Pb and Se varied with age, and Co and Zn with gender, which limited spatial comparisons across all populations to Cd, which was highest in Greenland bears. Collectively, geographic relationships appeared similar to past studies with little change in concentration over time in Canada and Greenland for most elements; Hg and Se were higher in some Canadian populations in 2002 as compared to 1982 and 1984. Concentrations of most elements in the polar bears did not exceed toxicity thresholds, although Cd and Hg exceeded levels correlated with the formation of hepatic lesions in laboratory animals.

The potential health effects of Salmonella found in wastewater residuals is dependent on the exposure of individuals to the organism. This paper provides a risk assessment for human infection from Salmonella due to direct contact with Class B biosolids, and from contact with Class A biosolids following regrowth of Salmonella. In addition, a risk assessment is provided for infection via airborne transport of bioaerosols from Class B biosolids and biosolids in which regrowth had occurred, to off-site communities. Results of the risk characterization imply that the risk of human infection from direct contact with Class B land applied residuals and subsequent ingestion is low. In contrast, the risk from direct contact with Class A residuals following regrowth is greater. Risks from airborne transport of Salmonella via bioaerosols away from a Class B land application site are also low. However, once again the risk from aerosols resulting from biosolids in which regrowth had occurred was greater. Based on these analyses, we conclude that it is highly unlikely that Salmonella infections will occur from land applied Class A or B residuals. However, risks become significant if Class A biosolids are stored anaerobically i.e. saturated, prior to land application.

The tropospheric level of the phytotoxic air pollutant ozone has considerably increased during the last century and is expected to continue to rise. Long-term exposures of higher plants to low ozone concentrations affect biochemical processes prior to any detectable symptoms of visible injury. On the other hand, the current critical level of ozone used to determine the threshold for damaging plants (biomass loss) is still based on the seasonal sum of the external concentrations of the pollutant above 40 nl l-1 (AOT40). Taking into account the stomatal conductance, a more relevant concept is based upon the actual ozone flux in the leaf through the stomata (cumulative uptake of ozone = CUO). CUO however ignores the internal capacity of leaf defense, which led to the concept of “effective ozone flux”, balance between stomatal flux and the intensity of cellular detoxification, with the aim to propose an improved threshold for ozone risk. Although the direct detoxification of ozone (and ROS issued from its decomposition) can primarily be carried out by cell wall ascorbate, the existing level of this antioxidant is not sufficient to indicate the degree of cell sensitivity. The capacity for regeneration of the antioxidant barrier is needed, implying the knowledge of the increased production of reducing power (NAD(P)H), primary supplier for detoxifying processes. It is made possible through the increased participation of the catabolic pathwaysand associated shunts which can provide NAD(P)H. In addition, the large change in the rubisco/PEPcase ratio, due to a huge increase in activity of the latter enzyme, leads to changes in carbon isotopic discrimination, which could be related to water use efficiency.Some results will be presented knowing that the challenge is to integrate the possible indicators in a leaf model to be used, through an upscaling process, in a tree and forest stand model.