Over 7500 entries, arranged under Ecological systems, Physical sciences applied to pollution, Effects of pollution, Air and water pollution, and Causes of pollution. Besides identification of the research, researcher, and institution, eachentry gives information about purpose, methods, progress, and source of support. Subject, researcher, supporting agency indexes.

For legacy and emerging persistent organic pollutants (POPs), surprisingly little is still known in quantitative terms about their global sources and emissions. Atmospheric transport has been identified as the key global dispersal mechanism for most legacy POPs. In contrast, transport by ocean currents may prove to be the main transport route for many polar, emerging POPs. This is linked to the POPs' intrinsic physico-chemical properties, as exemplified by the different fate of hexachlorocyclohexanes in the Arctic. Similarly, our current understanding of POPs' global transport and fate remains sketchy. The importance of organic carbon and global temperature differences have been accepted as key drivers of POPs' global distribution. However, future research will need to understand the various biogeochemical and geophysical cycles under anthropogenic pressures to be able to understand and predict the global fate of POPs accurately. Future studies into the global fate of POPs will need to pay more attention to the various biogeochemical and anthropogenic cycles to better understand emissions, transport and sinks.

This paper summarizes the historical and scientific foundations of the Linear No-Threshold (LNT) cancer risk assessment model. The story of cancer risk assessment is an extraordinary one as it was based on an initial incorrect gene mutation interpretation of Muller, the application of this incorrect assumption in the derivation of the LNT single-hit model, and a series of actions by leading radiation geneticists during the 1946–1956 period, including a National Academy of Sciences (NAS) Biological Effects of Atomic Radiation (BEAR) I Genetics Panel (Anonymous, 1956), to sustain the LNT belief via a series of deliberate obfuscations, deceptions and misrepresentations that provided the basis of modern cancer risk assessment policy and practices. The reaffirming of the LNT model by a subsequent and highly influential NAS Biological Effects of Ionizing Radiation (BEIR) I Committee (NAS/NRC, 1972) using mouse data has now been found to be inappropriate based on the discovery of a significant documented error in the historical control group that led to incorrect estimations of risk in the low dose zone. Correction of this error by the original scientists and the application of the adjusted/corrected data back to the BEIR I (NAS/NRC, 1972) report indicates that the data would have supported a threshold rather than the LNT model. Thus, cancer risk assessment has a poorly appreciated, complex and seriously flawed history that has undermined policies and practices of regulatory agencies in the U.S. and worldwide to the present time.

Forests in Europe face significant changes in climate, which in interaction with air quality changes, may significantly affect forest productivity, stand composition and carbon sequestration in both vegetation and soils. Identified knowledge gaps and research needs include: (i) interaction between changes in air quality (trace gas concentrations), climate and other site factors on forest ecosystem response, (ii) significance of biotic processes in system response, (iii) tools for mechanistic and diagnostic understanding and upscaling, and (iv) the need for unifying modelling and empirical research for synthesis. This position paper highlights the above focuses, including the global dimension of air pollution as part of climate change and the need for knowledge transfer to enable reliable risk assessment. A new type of research site in forest ecosystems (“supersites”) will be conducive to addressing these gaps by enabling integration of experimentation and modelling within the soil-plant-atmosphere interface, as well as further model development.

Tropospheric ozone (O3) was first determined to be phytotoxic to grapes in southern California in the 1950s. Investigations followed that showed O3 to be the cause of foliar symptoms on tobacco and eastern white pine. In the 1960s, “X” disease of ponderosa pines within the San Bernardino Mountains was likewise determined to be due to O3. Nearly 50 years of research have followed. Foliar O3 symptoms have been verified under controlled chamber conditions. Studies have demonstrated negative growth effects on forest tree seedlings due to season-long O3 exposures, but due to complex interactions within forest stands, evidence of similar losses within mature tree canopies remains elusive. Investigations on tree growth, O3 flux, and stand productivity are being conducted along natural O3 gradients and in open-air exposure systems to better understand O3 effects on forest ecosystems. Given projected trends in demographics, economic output and climate, O3 impacts on US forests will continue and are likely to increase. Elevated tropospheric ozone remains an important phytotoxic air pollutant over large areas of US forests.

European research efforts to address concerns in relation to increasing levels of marine litter and potential effects on ecosystems and human health have been launched. We assessed a total of 52 European projects which researched or contributed to the implementation of European marine litter legislation. These projects ranged from national initiatives, to large scale programmes involving multiple EU member states. The best represented topics within those European projects were ‘Policy, Governance and Management’ and ‘Monitoring’. Comparatively ‘Risk Assessment’, ‘Fragmentation’ and ‘Assessment Tools’ were underrepresented. The analyses showed that West-European countries have contributed more to marine litter research and therefore received more funding. As a result, thematic hotspots were present, and scientific capacity is concentrated by topic and countries. The results indicate the need to continue to support initiatives to cover clearly identified gaps, either geographic or thematic, to deliver risk assessments and recommendations to address the marine litter issue.

This paper reports the temporal variations, sources and transport characteristics of carbonaceous aerosol in Chongqing, a megacity in the Sichuan Basin. Hourly organic carbon (OC) and elemental carbon (EC) mass concentrations in PM₂.₅ were measured at an urban supersite from November 2019 to October 2020. The annual mean PM₂.₅, OC and EC concentrations (±1SD) were 38.50 ± 25.79 μg/m³, 9.03 ± 5.73 and 2.45 ± 1.47 μgC/m³, respectively. An intensive influence of biomass combustion was found during the observation period. Strong seasonality of carbonaceous aerosol with highest concentrations in winter and lowest concentrations in summer was observed. Meanwhile, two diverse pathways for secondary formation dominated in different seasons. One was highly related to gas-phase photochemical oxidation under high temperature and radiation, and another was highly related to heterogeneous reactions, while the latter was more significant, especially in winter. Diurnal and quarterly variation patterns for carbonaceous aerosol showed that the development of planetary boundary layer strongly influenced carbonaceous aerosol concentrations. Moreover, the regional sources from the northeast within the basin were identified as major contributors of the primary carbonaceous aerosol to Chongqing, while secondary components were more from local sources than regional transport. This study highlights the importance of prioritising the abatement of gaseous precursors for carbonaceous aerosol and an urgent need for the inter-regional prevention and control measures of the cities located in the Sichuan basin, especially the cities in the northeast of urban Chongqing.

This study evaluates the carcinogenic and the non-carcinogenic health risks related to non-methane volatile organic compounds (NMVOCs) and elements, dioxins, furans, dioxin-like polychlorobiphenyls, phthalates and polycyclic aromatic hydrocarbons in PM₂.₅ samples collected during a one-year field campaign in two urban industrial areas in the East Mediterranean region. The health risk was assessed for the three exposure pathways (ingestion, inhalation and dermal contact) and for different age categories (newborns, children, adolescents, and adults). The non-carcinogenic risk calculated for the different species showed that benzene and n-heptane explained 78–94% of the total hazard index (HI) for NMVOCs at both sites. The total HI for NMVOCs varied between 2.9 and 26.8 at Zouk and between 0.8 and 6.6 at Fiaa for adults and newborns respectively exceeding the recommended USEPA limit of 1 for most age categories. PM₂.₅-bound elements had values higher than the recommended USEPA limit for newborns with Mn, Pb, V, and Ni as the major contributors. The other species under study presented moderate risk values. The lifetime cancer risk due only to the exposure to NMVOCs was 170 and 46 times higher than the threshold limit at Zouk and Fiaa, respectively. PM₂.₅-bound PAHs, As, Co, Cr(VI), Ni and V concentrations showed lifetime cancer risk exceeding the threshold limit of 10⁻⁶ with 58 and 28 additional cancer cases per million habitats at Zouk and Fiaa, respectively. To our knowledge, this assessment is a first evaluating the health risk of several classes of compounds from both particulate and gas phases.