Prior to 1985 the Food and Agriculture Organization (FAO) estimated global food crop contamination with mycotoxins to be 25%. The origin of this statement is largely unknown. To assess the rationale for it, the relevant literature was reviewed and data of around 500,000 analyses from the European Food Safety Authority and large global survey for aflatoxins, fumonisins, deoxynivalenol, T-2 and HT-2 toxins, zearalenone and ochratoxin A in cereals and nuts were examined. Using different thresholds, i.e. limit of detection, the lower and upper regulatory limits of European Union (EU) legislation and Codex Alimentarius standards, the mycotoxin occurrence was estimated. Impact of different aspects on uncertainty of the occurrence estimates presented in literature and related to our results are critically discussed. Current mycotoxin occurrence above the EU and Codex limits appears to confirm the FAO 25% estimate, while this figure greatly underestimates the occurrence above the detectable levels (up to 60-80%). The high occurrence is likely explained by a combination of the improved sensitivity of analytical methods and impact of climate change. It is of immense importance that the detectable levels are not overlooked as through diets, humans are exposed to mycotoxin mixtures which can induce combined adverse health effects.

Hg 0 + I 2 → HgI 2 Absolute N 2 , 1 atm 296 ± 1 < (1.27 ± 0.58) × 10 -19 Raofie et al. 2 M06-2X/aug-cc-pVTZ-PP High pressure limit 3.94 × 10 -14 T 1.06 e -159080/RT Auzmendi-Murua et al. 3 Hg 0 + I → HgI RRKM/B3LYP N 2 , 1 atm 180-400 4.0 × 10 -13 (T/298) -2.38 Goodsite et al. 4 Hg 0 + Br 2 → HgBr 2 Absolute Air, N 2 , 1 atm 298 ± 1 < (9 ± 2) × 10 -17 Ariya et al. 5 Absolute Air, 1 atm ∼298 No reaction detected Sumner et al. 6 Absolute Air, 1 atm 296 (6.0 ± 0.5) × 10 -17 Liu et al. 7 CCSD(T)/AVTZ 1 atm 298-2000 1.62 -9 e -110800/RT Wilcox and Okano 8 M06-2X/aug-cc-pVTZ-PP High pressure limit 4.70 × 10 -14 T 1.06 e -169190/RT Auzmendi-Murua et al. 3 Hg 0 + BrO → HgBrO Relative N 2 , 1 atm 298 10 -15 < k < 10 -13 Raofie and Ariya 9 Hg 0 + Br → HgBr Ab initio N/A, 1 atm 1.01 × 10 -12 e 1738/RT Khalizov et al. 10 RRKM/B3LYP N 2 , 1 atm 200-300 3.7 × 10 -13 (T/298) -2.76 Goodsite et al. 4 ; Goodsite et al. 11 Absolute N 2 , 0.26-0.79 atm 243-293 (1.46 ± 0.36) × 10 -32 [cm 6 molec -2 s -1 ] Donohoue et al. 12 (T/298) (-1.86±1.49) CCSD(T) Ar, 1 atm 260 1.2 × 10 -12 Shepler et al. 13 Relative Air, N 2 , 1 atm 298 ± 1 (3.2 ± 0.9) × 10 -12 Ariya et al. 5 Absolute CF 3 Br, 0.26 atm 397 ~3 × 10 -16 molec -1 s -1 Greig, G. et al. 14 CCSD(T)/AVTZ 1 atm 298-2000 6.64 × 10 -14 (T/298) -0.859 Wilcox and Okano HgBr + Br → HgBr 2 Absolute CF 3 Br, 0.26 atm 397 ~7 × 10 -14 Greig, G. et al. 14 RRKM/B3LYP N 2 , 1 atm 180-400 2.5 × 10 -10 (T/298) -0.57 Goodsite et al. 4 CCSD(T)/AVTZ 1 atm 298-2000 3.32 × 10 -12 (T/298) -9.18 Wilcox and Okano CCSD(T)/aVTZ 1 atm 298 6.33 × 10 -11 Dibble et al. 15 ; Wang et al.

Global trade of agricultural commodities (e.g., animal feed) requires monitoring for fungal toxins. Also, little is known about masked and emerging toxins and metabolites. 1926 samples from 52 countries were analysed for toxins and metabolites. Of 162 compounds detected, up to 68 metabolites were found in a single sample. A subset of 1113 finished feed, maize and maize silage samples containing 57 compounds from 2012 to 2015 from 44 countries was investigated using liquid chromatography and mass spectrometry. Deoxynivalenol (DON), zearalenone (ZEN) and fumonisins showed large increases of annual medians in Europe. Within a region, distinct trends were observed, suggesting importance of local meteorology and cultivars. In 2015, median DON concentrations increased to 1400 μg·kg−1 in Austria, but were stable in Germany at 350 μg·kg−1. In 2014, enniatins occurred at median concentrations of 250 μg·kg−1 in Europe, at levels similar to DON and ZEN. The latter were frequently correlated with DON-3-glucoside and ZEN-14-sulfate. Co-occurrence of regulated toxins was frequent with e.g., enniatins, and moniliformin. Correlation was observed between DON and DON-3-glucoside and with beauvericin. Results indicate that considerably more than 25% of agricultural commodities could be contaminated with mycotoxins as suggested by FAO, although this is at least partly due to the lower limits of detection in the current survey. Observed contamination percentages ranged from 7.1 to 79% for B trichothecenes and 88% for ZEN.

The importance of organic compounds in the oxidative capacity of the atmosphere, and as cloud condensation and ice-forming nuclei, has been recognized for several decades. Organic compounds comprise a significant fraction of the suspended matter mass, leading to local (e.g. toxicity, health hazards) and global (e.g. climate change) impacts. The state of knowledge of the physical chemistry of organic aerosols has increased during the last few decades. However, due to their complex chemistry and the multifaceted processes in which they are involved, the importance of organic aerosols, particularly bioaerosols, in driving physical and chemical atmospheric processes is still very uncertain and poorly understood. Factors such as solubility, surface tension, chemical impurities, volatility, morphology, contact angle, deliquescence, wettability, and the oxidation process are pivotal in the understanding of the activation processes of cloud droplets, and their chemical structures, solubilities and even the molecular configuration of the microbial outer membrane, all impact ice and cloud nucleation processes in the atmosphere. The aim of this review paper is to assess the current state of knowledge regarding chemical and physical characterization of bioaerosols with a focus on those properties important in nucleation processes. We herein discuss the potential importance (or lack thereof) of physical and chemical properties of bioaerosols and illustrate how the knowledge of these properties can be employed to study nucleation processes using a modeling exercise. We also outline a list of major uncertainties due to a lack of understanding of the processes involved or lack of available data. We will also discuss key issues of atmospheric significance deserving future physical chemistry research in the fields of bioaerosol characterization and microphysics, as well as bioaerosol modeling. These fundamental questions are to be addressed prior to any definite conclusions on the potential significance of the role of bioaerosols on physico-chemical atmospheric processes and that of climate.

Abstract. L. Zhang et al. (2012), in a recent report, compared model estimates with new observations of oxidized and particulate mercury species (Hg2+ and Hgp) in the Great Lakes region and found that the sum of Hg2+ and Hgp varied between a factor of 2 to 10 between measurements and model. They suggested too high emission inputs as Hg2+ and too fast oxidative conversion of Hg0 to Hg2+ and Hgp as possible causes. This study quantitatively explores measurement uncertainties in detail. These include sampling efficiency, composition of sample, interfering species and calibration errors. Model (Global/Regional Atmospheric Heavy Metals Model – GRAHM) sensitivity experiments are used to examine the consistency between various Hg measurements and speciation of Hg near emission sources to better understand the discrepancies between modelled and measured concentrations of Hg2+ and Hgp. We find that the ratio of Hg0, Hg2+ and Hgp in the emission inventories, measurements of surface air concentrations of oxidized Hg and measurements of wet deposition are currently inconsistent with each other in the vicinity of emission sources. Current speciation of Hg emissions suggests higher concentrations of Hg2+ in air and in precipitation near emission sources; however, measured air concentrations of Hg2+ and measured concentrations of Hg in precipitation are not found to be significantly elevated near emission sources compared to the remote regions. The averaged unbiased root mean square error (RMSE) between simulated and observed concentrations of Hg2+ is found to be reduced by 42% and for Hgp reduced by 40% for 21 North American sites investigated, when a ratio for Hg0 : Hg2+ : Hgp in the emissions is changed from 50 : 40 : 10 (as specified in the original inventories) to 90 : 8 : 2. Unbiased RMSE reductions near emissions sources in the eastern United States and Canada are found to be reduced by up to 58% for Hg2+. Significant improvement in the model simulated spatial distribution of wet deposition of mercury in North America is noticed with the modified Hg emission speciation. Measurement-related uncertainties leading to lower estimation of Hg2+ concentrations are 86%. Uncertainties yielding either to higher or lower Hg2+ concentrations are found to be 36%. Finally, anthropogenic emission uncertainties are 106% for Hg2+. Thus it appears that the identified uncertainties for model estimates related to mercury speciation near sources, uncertainties in measurement methodology and uncertainties in emissions can close the gap between modelled and observed estimates of oxidized mercury found in L. Zhang et al. (2012). Model sensitivity simulations show that the measured concentrations of oxidized mercury, in general, are too low to be consistent with measured wet deposition fluxes in North America. Better emission inventories (with respect to speciation), better techniques for measurements of oxidized species and knowledge of mercury reduction reactions in different environments (including in-plume) in all phases are needed for improving the mercury models.