Jacob K. Nøjgaard

Eye complaints in the office environment: precorneal tear film integrity influenced by eye blinking efficiency.

To achieve a common base for understanding work related eye complaints in the office environment, it is necessary to merge approaches from indoor air science, occupational health, and ophthalmology. Based on database searches, it is concluded that precorneal tear film (PTF) alteration leads to eye complaints that may be caused by: (1) thermal factors (low relative humidity; high room temperature); (2) demanding task content (attention decreases blinking and widens the exposed ocular surface area); and (3) individual characteristics (for example, tear film alterations, blinking anomalies, gland dysfunctions, and use of contact lenses). These factors and conditions are able to progressively increase water evaporation and faster thinning of the PTF, which causes dryness and dry spot formation on the cornea, possibly followed by corneal and conjunctiva epithelial alterations and eye complaints. Another possible cause of eye complaints is certain irritating chemical compounds, in addition to oxidation mixtures that are formed in reactions between ozone and unsaturated organic compounds (alkenes). The effect may be exacerbated by low relative humidity.

Effect of vitamin C and iron chelation on diesel exhaust particle and carbon black induced oxidative damage and cell adhesion molecule expression in human endothelial cells

Exposure to particulate matter is associated with oxidative stress and risk of cardiovascular diseases. We investigated if vitamin C and desferrioxamine (iron chelator) altered the levels of oxidative stress and expression of cell adhesion molecules upon exposure to diesel exhaust particles (DEP) and carbon black in cultured human umbilical vein endothelial cells (HUVECs). We found that the particles were only slightly cytotoxic in the high concentration ranges. Particle-induced intracellular reactive oxygen species (ROS) production was attenuated by vitamin C administration or iron chelation and particularly when combined (p<0.001). Only desferrioxamine protected the DNA from oxidative damage in terms of strand breaks and formamidopyrimidine DNA glycosylase sensitive sites induced by carbon black (p<0.01). Carbon black and small sized DEP generated from an Euro4 engine increased the surface expression of VCAM-1 and ICAM-1, whereas DEP from an engine representing an old combustion type engine (SRM2975) with larger particles did not affect the expression of cell adhesion molecules. These effects were also attenuated by desferrioxamine but not vitamin C. The study shows that exposure to carbon black and DEP in HUVECs can generate both oxidative stress and expression of cell surface adhesion molecules and that these effects can in part be attenuated by vitamin C and desferrioxamine.

Characterization of humic-like substances in Arctic aerosols

Humic-like substances (HULIS) are a complex group of relatively high molecular weight organic compounds which contribute considerably to the mass of organic carbon (OC) and influence the light-absorbing properties of aerosols. In this work, HULIS were investigated for the first time in the high-Arctic atmosphere, focusing on the chemical characterization and mass contribution of HULIS to the total suspended particle (TSP) mass using weekly aerosol samples collected at Station Nord, northeast Greenland every fourth week during 2010. Average HULIS-C concentration was 11 ng C m−3 during the darker months (November–April) and 4 ng C m−3 during the other months (May–October) with an annual mass concentration of 0.02 ± 0.01 µg m−3. HULIS-C contributed to 3–16% of water-soluble organic carbon (WSOC), whereas HULIS accounted for 0.7–4.1% of TSP mass, with TSP typically below 1.0 µg m−3. Concentrations of OC, WSOC, HULIS, selected HULIS functional groups (carboxylic acids, aromatic carboxylic acids, and organosulfates) and levoglucosan overlapped with the typical Arctic haze pattern with elevated concentrations during winter to early spring. The aromatic carboxylic acid portion accounted for a larger share of total carboxylic acid of HULIS during the darker months (7%) compared to the brighter months (3%). The more abundant aromatic carboxylic acid functional groups and the moderate correlation between HULIS and levoglucosan concentrations during the darker months both indicate that biomass burning aerosols and thereby emissions of aromatic compounds could contribute to HULIS in the Arctic, especially during late winter. During the brighter months, relatively higher average molecular weight of HULIS was observed.

Indoor measurements of the sum of the nitrate radical, NO3, and nitrogen pentoxide, N2O5 in Denmark.

There is a need for indoor measurements of nitrate radicals (NO(3)) and nitrogen pentoxide (N(2)O(5)) to better understand removal and transformation of volatile organic compounds in indoor environments, and to evaluate the possible health effects from exposure to nitrated reaction products. NO(3) and NO(2) react to form N(2)O(5) in the presence of a third molecule, and the fast equilibrium necessitates measurements of both NO(3) and N(2)O(5) in the evaluation of indoor NO(3) chemistry. The sum of these two species, NO(3)( *), was quantified in an office building in Denmark by measuring an oxidation product of the cyclohexene/NO(3) reaction in a flow-tube set-up. NO(3)( *) concentrations ranged from 1 to 58ppt, where N(2)O(5) was estimated to account for more than 68%. The concentrations of the precursors, NO(2) and O(3), and the photolysis of NO(3) were parameters, which clearly influenced NO(3)( *) apparent from the different precursor concentrations, lighting and daylight versus dark samples in this study. Also indoor air pollutants, in particular alkenes such as limonene and alpha-pinene, can significantly reduce NO(3)( *). These first indoor measurements of NO(3)( *), warrant further high time resolution measurements of NO(3), N(2)O(5), and organic nitrates indoors.

Regions of open water and melting sea ice drive new particle formation in North East Greenland

Atmospheric new particle formation (NPF) and growth significantly influences the indirect aerosol-cloud effect within the polar climate system. In this work, the aerosol population is categorised via cluster analysis of aerosol number size distributions (9–915 nm, 65 bins) taken at Villum Research Station, Station Nord (VRS) in North Greenland during a 7 year record (2010–2016). Data are clustered at daily averaged resolution; in total, we classified six categories, five of which clearly describe the ultrafine aerosol population, one of which is linked to nucleation events (up to 39% during summer). Air mass trajectory analyses tie these frequent nucleation events to biogenic precursors released by open water and melting sea ice regions. NPF events in the studied regions seem not to be related to bird colonies from coastal zones. Our results show a negative correlation (r = −0.89) between NPF events and sea ice extent, suggesting the impact of ultrafine Arctic aerosols is likely to increase in the future, given the likely increased sea ice melting. Understanding the composition and the sources of Arctic aerosols requires further integrated studies with joint multi-component ocean-atmosphere observation and modelling.

Atmospheric Pollution Research on Greenland

Danish studies in the Arctic atmosphere were almost all carried out on Greenland. There were not any specific programmes within IPY but activities were performed in the framework of Arctic Monitoring and Assessment Programme (AMAP) Financed from Denmark by means from DANCEA. A long series of studies in other spheres than the atmosphere have also been carried out but they will not be described here as they are beyond the scope of this chapter.