The epiphytic lichen flora of 25 European ICP-IM monitoring sites, all situated remote from air pollution sources, was statistically related to measured levels of SO2 in air, NH4+, NO3− and SO42− in precipitation, annual bulk precipitation, and annual average temperature. Significant regression models were calculated for eleven acidophytic species. Several species strong negative correlation with nitrogen compounds. At concentrations as low as 0·3 mg N l−1 in precipitation, a decrease of the probability of occurrence is observed for Bryoria capillaris, B. fuscescens, Cetraria pinastri, Imshaugia aleurites and Usnea hirta. The observed pattern correlations strongly suggests a key role of NH4+ in determining the species occurrence, additional role of NO3− cannot be ruled out. Some species show a distinct response to current of SO2 well. It may be concluded that long distance nitrogen air pollution has strong influence the occurrence of acidophytic lichen species.
The threshold of toxicological concern (TTC) concept is well established for assessing human safety of food-contact substances and has been reapplied for a variety of endpoints, including carcinogenicity, teratogenicity, and reproductive toxicity. The TTC establishes an exposure level for chemicals below which no appreciable risk to human health or the environment is expected, based on a de minimis value for toxicity identified for many chemicals. Threshold of toxicological concern approaches have benefits for screening-level risk assessments, including the potential for rapid decision-making, fully utilizing existing knowledge, reasonable conservativeness for chemicals used in lower volumes (low production volume chemicals (e.g., < 1 t/yr), and reduction or elimination of unnecessary animal tests. Higher production volume chemicals (>1 t/yr) would in principle always require specific information because of the presumed higher exposure potential. The TTC approach has found particular favor in the assessment of chemicals used in cosmetics and personal care products, as well as other chemicals traditionally used in low volumes. Use of the TTC in environmental safety is just beginning, and initial attempts are being published. Key questions focus on hazard extrapolation of diverse taxa across trophic levels, importance of mode of action, and whether safe concentrations for ecosystems estimated from acute or chronic toxicity data are equally useful and in what contexts. The present study provides an overview of the theoretical basis for developing an ecological (eco)-TTC, with an initial exploration of chemical assessment and boundary conditions for use. An international collaboration under the International Life Sciences Institute Health and Environmental Sciences Institute has been established to address challenges related to developing and applying useful eco-TTC concepts. Environ Toxicol Chem 2015;34:2864-2869. # 2015 SETAC
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