Comparing the lung cancer burden of ambient particulate matter using scenarios of air quality standards versus acceptable risk levels.

OBJECTIVES: Ambient particulate matter (PM) is regulated with science-based air quality standards, whereas carcinogens are regulated with a number of "acceptable" cases. Given that PM is also carcinogenic, we identify differences between approaches. METHODS: We assessed the lung cancer deaths for Switzerland attributable to exposure to PM up to 10 µm (PM10) and to five particle-bound carcinogens. For PM10, we used an epidemiological approach based on relative risks with four exposure scenarios compared to two counterfactual concentrations. For carcinogens, we used a toxicological approach based on unit risks with four exposure scenarios. RESULTS: The lung cancer burden using concentrations from 2010 was 10-14 times larger for PM10 than for the five carcinogens. However, the burden depends on the underlying exposure scenarios, counterfactual concentrations and number of carcinogens. All scenarios of the toxicological approach for five carcinogens result in a lower burden than the epidemiological approach for PM10. CONCLUSIONS: Air quality standards-promoted so far by the WHO Air Quality Guidelines-provide a more appealing framework to guide health risk-oriented clean air policymaking than frameworks based on a number of "acceptable" cases.

Epidemiological analysis of ozone and nitrogen impacts on vegetation - Critical evaluation and recommendations.

For human health studies, epidemiology has been established as important tool to examine factors that affect the frequency and distribution of disease, injury, and other health-related events in a defined population, serving the purpose of establishing prevention and control programs. On the other hand, gradient studies have a long tradition in the research of air pollution effects on plants. While there is no principal difference between gradient and epidemiological studies, the former address more one-dimensional transects while the latter focus more on populations and include more experience in making quantitative predictions, in dealing with confounding factors and in taking into account the complex interplay of different factors acting at different levels. Epidemiological analyses may disentangle and quantify the contributions of different predictor variables to an overall effect, e.g. plant growth, and may generate hypotheses deserving further study in experiments. Therefore, their use in ecosystem research is encouraged. This article provides a number of recommendations on: (1) spatial and temporal aspects in preparing predictor maps of nitrogen deposition, ozone exposure and meteorological covariates; (2) extent of a dataset required for an analysis; (3) choice of the appropriate regression model and conditions to be satisfied by the data; (4) selection of the relevant explanatory variables; (5) treatment of interactions and confounding factors; and (6) assessment of model validity.

Using change-point models to estimate empirical critical loads for nitrogen in mountain ecosystems.

To protect ecosystems and their services, the critical load concept has been implemented under the framework of the Convention on Long-range Transboundary Air Pollution (UNECE) to develop effects-oriented air pollution abatement strategies. Critical loads are thresholds below which damaging effects on sensitive habitats do not occur according to current knowledge. Here we use change-point models applied in a Bayesian context to overcome some of the difficulties when estimating empirical critical loads for nitrogen (N) from empirical data. We tested the method using simulated data with varying sample sizes, varying effects of confounding variables, and with varying negative effects of N deposition on species richness. The method was applied to the national-scale plant species richness data from mountain hay meadows and (sub)alpine scrubs sites in Switzerland. Seven confounding factors (elevation, inclination, precipitation, calcareous content, aspect as well as indicator values for humidity and light) were selected based on earlier studies examining numerous environmental factors to explain Swiss vascular plant diversity. The estimated critical load confirmed the existing empirical critical load of 5-15 kg N ha-1 yr-1 for (sub)alpine scrubs, while for mountain hay meadows the estimated critical load was at the lower end of the current empirical critical load range. Based on these results, we suggest to narrow down the critical load range for mountain hay meadows to 10-15 kg N ha-1 yr-1.

Nitrogen deposition and multi-dimensional plant diversity at the landscape scale.

Estimating effects of nitrogen (N) deposition is essential for understanding human impacts on biodiversity. However, studies relating atmospheric N deposition to plant diversity are usually restricted to small plots of high conservation value. Here, we used data on 381 randomly selected 1 km(2) plots covering most habitat types of Central Europe and an elevational range of 2900 m. We found that high atmospheric N deposition was associated with low values of six measures of plant diversity. The weakest negative relation to N deposition was found in the traditionally measured total species richness. The strongest relation to N deposition was in phylogenetic diversity, with an estimated loss of 19% due to atmospheric N deposition as compared with a homogeneously distributed historic N deposition without human influence, or of 11% as compared with a spatially varying N deposition for the year 1880, during industrialization in Europe. Because phylogenetic plant diversity is often related to ecosystem functioning, we suggest that atmospheric N deposition threatens functioning of ecosystems at the landscape scale.

Establishing the link between ammonia emission control and measurements of reduced nitrogen concentrations and deposition.

In the context of international efforts to reduce the impacts of atmospheric NH3 and NH4+ (collectively, NHx). it is important to establish the link between NH3 emissions and monitoring of NHx concentrations and deposition. This is equally relevant to situations where NH3 emissions changes are certain (e.g. due to changed source sector activity), as to cases where NH3 abatement technologies have been implemented. Correct interpretation of adequate atmospheric measurements is essential, since monitoring data provide the only means to evaluate trends in regional NH3 emissions. These issues have been reviewed using available measurements and modelling from nine countries. In addition to historic datasets, the analysis here considers countries where NH3 source sector activity changed (both increases and decreases) and countries where NH3 abatement policies have been implemented. In The Netherlands an 'ammonia gap' was identified between the expected reduction and results of monitoring, and was attributed initially to ineffectiveness of the abatement measures. The analysis here for a range of countries shows that atmospheric interactions complicate the expected changes, particularly since SO2 emissions have decreased at the same time, while at many sites the few years of available data show substantial inter-annual variation. It is concluded that networks need to be established that speciate between NH3 and aerosol NH4+, in addition to providing wet deposition, and sample at sufficient sites for robust regional estimates to be established. Such measurements will be essential to monitor compliance of the international agreements on NH3 emission abatement.