Helle Vibeke Andersen

Personal exposure to PM2.5, black smoke and NO2 in Copenhagen: relationship to bedroom and outdoor concentrations covering seasonal variation

Epidemiological studies have found negative associations between human health and particulate matter in urban air. In most studies outdoor monitoring of urban background has been used to assess exposure. In a field study, personal exposure as well as bedroom, front door and background concentrations of PM2.5, black smoke (BS), and nitrogen dioxide (NO2) were measured during 2-day periods in 30 subjects (20–33 years old) living and studying in central parts of Copenhagen. The measurements were repeated in the four seasons. Information on indoor exposure sources such as environmental tobacco smoke (ETS) and burning of candles was collected by questionnaires. The personal exposure, the bedroom concentration and the front door concentration was set as outcome variable in separate models and analysed by mixed effect model regression methodology, regarding subject levels as a random factor. Seasons were defined as a dichotomised grouping of outdoor temperature (above and below 8°C). For NO2 there was a significant association between personal exposure and both the bedroom, the front door and the background concentrations, whereas for PM2.5 and BS only the bedroom and the front door concentrations, and not the background concentration, were significantly associated to the personal exposure. The bedroom concentration was the strongest predictor of all three pollution measurements. The association between the bedroom and front door concentrations was significant for all three measurements, and the association between the front door and the background concentrations was significant for PM2.5 and NO2, but not for BS, indicating greater spatial variation for BS than for PM2.5 and NO2. For NO2, the relationship between the personal exposure and the front door concentration was dependent upon the “season”, with a stronger association in the warm season compared with the cold season, and for PM2.5 and BS the same tendency was seen. Time exposed to burning of candles was a significant predictor of personal PM2.5, BS and NO2 exposure, and time exposed to ETS only associated with personal PM2.5 exposure. These findings imply that the personal exposure to PM2.5, BS and NO2 depends on many factors besides the outdoor levels, and that information on, for example, time of season or outdoor temperature and residence exposure, could improve the accuracy of the personal exposure estimation.

Pressure pain sensitivity and hardness along human normal and sensitized muscle.

The spatial distribution of pressure sensitivity and muscle hardness was examined on normal muscle tissue and muscle tissue after induction of delayed onset muscle soreness (DOMS). The pressure sensitivity and muscle hardness were assessed at nine sites on the tibialis muscle from the proximal to distal tendon on two separate days. In total 37 healthy volunteers participated in three experiments. In the first experiment pressure pain threshold (PPT) and pressure pain tolerance (PPTO) were assessed. Decreased PPT and PPTO were found on day 2, 7 days after day 1. Proximal and distal stimulation sites were harder compared to muscle belly sites. In a second experiment two different probe sizes were used. Variation in PPT between the nine sites was found for the large probe with muscle belly being less sensitive to pressure stimulation compared to proximal and distal sites. The most proximal stimulation site was harder compared to muscle belly sites. In a third experiment PPT and muscle hardness were assessed before and 48 h after eccentric exercise. PPT at two muscle belly sites was significantly decreased during DOMS. No specific sites were harder during DOMS, the average muscle hardness across sites was however significantly increased. Decreased PPT and increased muscle hardness did not correlate. In conclusion, within subjects the pressure sensitivity varies along the musculoskeletal unit. In DOMS, specific muscle belly sites were more sensitive to pressure stimulation. Muscle–tendon sites were harder compared to muscle belly sites.

Review of dry deposition measurements of ammonia and nitric acid to forest

The paper describes some general aspects of the estimation of dry deposition fluxes and reviews the measurements of dry deposition of atmospheric gaseous ammonia and nitric acid in relation to forests. The dry deposition of ammonia is shown to be a bi-directional surface flux, i.e. the forest receives a nitrogen input from ammonia in the air, though some ammonia apparently is also emitted from the forest. Still, atmospheric ammonia originating from agricultural activities contributes with large amounts of nitrogen to the ecosystems. Nitric acid seems to deposit very fast, though only very few flux measurements above forest are reported. The method for estimating the fluxes of nitric acid might be questionable for some conditions. For the investigations reported the concentration levels of nitric acid have been relatively low and this compound has contributed with moderate loads of nitrogen to the ecosystem.

Human exposure to traffic pollution. Experience from Danish studies

Air pollution may have severe long-term as well as short-term health effects. The determination of possible links between pollution levels and impact on human health is, however, not a straightforward task. A key problem is the assessment of human exposure to ambient pollution levels. In later years, the possible role of particulate pollution as a health hazard has drawn major attention and is, therefore, the subject of research projects in many countries including Denmark. The present paper gives a review of recent and ongoing/planned Danish air pollution exposure studies. Furthermore, key results from Danish studies of ultrafine particles from urban traffic are outlined. The exposure studies show that air pollution models may be strong tools in impact assessment studies, especially when used in combination with personal exposure monitoring and application of biomarkers. Personal exposure measurements in Copenhagen indicate that indoor pollution levels may be very important for the personal exposure to fine fraction particles (PM2.5). Measurements with a differential mobility analyzer (DMA) in Danish urban areas show that number concentrations of ultrafine particles (<100 nm) in busy streets are strongly correlated with classic traffic pollutants such as nitrogen oxides and carbon monoxide. The number concentrations in urban Danish streets have decreased considerably between two campaigns in 1999 and 2000, apparently as a result of reductions in sulfur contents in Danish diesel fuels that took place in July 1999.

Measurements of ammonia and ammonium by denuder and filter pack

Abstract Simultaneous 24-hour measurements of gaseous ammonia (NH3) and particulate ammonium (NH4+) by denuder and filter pack were carried out at five different locations in Denmark. The locations represent areas surrounded by different emission densities of NH3. In general a good agreement was found for the determination of the sum of NH3 plus NH4+ by the two methods at all locations. The NH4+ determination by the two methods was in general found to be in good agreement. Even though sampling artifacts are seen for the NH3 determination by the filter pack, the NH3 concentrations are in general too low to affect the correlation of particulate NH4+. At a location surrounded by areas with NH3 emission densities the separate determinations of NH3 and NH4+ by the filter pack were in general in good agreement with the denuder determination of, respectively, NH3 and NH4+. At the other locations, the NH3 determination by filter pack frequently showed underestimation compared to the denuder. The under-estimation was frequently observed at conditions with low NH3 concentrations, westerly winds and a low ratio of particle NH4+ relative to particulate SO42− and NO3−. It probably relates to conditions with unsaturated acidic aerosols absorbing the NH3. The observations show that the ability of the filter pack method for NH3 determination is dependent on the climate, pollution climate and surrounding NH3 emission density. The use of the filter pack method and its restrictions therefore demand an individual investigation of the sampling site characteristics.

Measurements of ammonia flux to a spruce stand in Denmark

Abstract This work demonstrates the existence of a linear relation between the deposition velocity of ammonia and the friction velocity measured above a spruce stand in the western part of Denmark. In order to estimate the ammonia deposition velocity and flux to a Norway spruce forest, concentration gradients of ammonia and several meteorological parameters were measured in a meteorology tower during two periods, 1 week in spring and 1 week in late summer 1991. The estimated deposition velocities lie in the range −0.125 to 0.201 m s−1, with a mean of 0.026 m s−1. The deposition velocity and the flux were generally largest in the afternoon. On the basis of 24-h measurements of ammonia and routine meteorological measurements the relation between deposition velocity and friction velocity is extrapolated to an estimate of the average flux for the growing season May to September 1991. The estimate gave an average flux of 87 μg NH3N m−2 h−1 (=0.02 μg NH3N m−2 s−1). The average deposition velocity for the period was 0.045 m s−1.

Residential exposure to outdoor air pollution from livestock operations and perceived annoyance among citizens

Epidemiological studies have shown that residential exposure to livestock odors can affect the health and wellbeing of rural citizens. However, exposure-response models for this relationship have not been developed. One of the main challenges is to identify a compound that can be used as proxy for livestock odor exposure. In this paper we developed models that describe the relationship between long-term averaged outdoor residential ammonia (NH(3)) exposures and livestock odor annoyance experienced by rural residents, and investigated person-related variables associated with annoyance responses. We used emission-based atmospheric dispersion modeling data to estimate household-specific outdoor concentrations and survey data to characterize the study subjects. Binomial and multinomial logistic regressions were used for model development. Residential NH(3) exposure was positively associated with moderate, high and extreme odor annoyance (adjusted odds ratio=10.59; 95% confidence interval: 1.35-83.13, for each unit increase in Log(e)NH(3) exposure). Specific characteristics of the exposed subjects (i.e., age, time per week spent at home, presence of children at home and job) act as co-determinants of odor annoyance responses. Predictive models showed classification accuracies of 67-72%. The results suggest that NH(3) exposure in the residential outdoor environment can be used as a predictor of livestock odor annoyance in population studies.

Adaptations of upper trapezius muscle activity during sustained contractions in women with fibromyalgia

The study compared the distribution of electromyographic (EMG) signal amplitude in the upper trapezius muscle in 10 women with fibromyalgia and in 10 healthy women before and after experimentally-induced muscle pain. Surface EMG signals were recorded over the right upper trapezius muscle with a 10 x 5 grid of electrodes during 90 degrees shoulder abduction sustained for 60s. The control subjects repeated the abduction task following injections of isotonic and hypertonic (painful) saline into the upper trapezius muscle. The EMG amplitude was computed for each electrode pair and provided a topographical map of the distribution of muscle activity. The pain level rated by the patients at the beginning of the sustained contraction was 5.9+/-1.5. The peak pain intensity for the control group following the injection of hypertonic saline was 6.0+/-1.6. During the sustained contractions, the EMG amplitude increased relatively more in the cranial than caudal region of the upper trapezius muscle for the control subjects (shift in the distribution of EMG amplitude: 2.3+/-1.3mm; P<0.01). The patient group showed lower average EMG amplitude than the controls during the contraction (P<0.05) and did not show different changes in EMG amplitude between different regions of the upper trapezius. A similar behavior was observed for the control group following injection of hypertonic saline. The results indicate that muscle pain prevents the adaptation of upper trapezius activity during sustained contractions as observed in non-painful conditions, which may induce overuse of similar muscle compartments with fatigue.

Perceived annoyance from environmental odors and association with atmospheric ammonia levels in non-urban residential communities: a cross-sectional study

ObjectiveOdor exposure is an environmental stressor that is responsible of many citizens complains about air pollution in non-urban areas. However, information about the exposure-response relation is scarce. One of the main challenges is to identify a measurable compound that can be related with odor annoyance responses. We investigated the association between regional and temporal variation of ammonia (NH3) concentrations in five Danish non-urban regions and environmental odor annoyance as perceived by the local residents.MethodsA cross-sectional study where NH3 concentration was obtained from the national air quality monitoring program and from emission-dispersion modelling, and odor pollution perception from questionnaires. The exposure-response model was a sigmoid model. Linear regression analyses were used to estimate the model constants after equation transformations. The model was validated using leave-one-out cross validation (LOOCV) statistical method.ResultsAbout 45% of the respondents were annoyed by odor pollution at their residential areas. The perceived odor was characterized by all respondents as animal waste odor. The exposure-annoyance sigmoid model showed that the prevalence of odor annoyance was significantly associated with NH3 concentrations (measured and estimated) at the local air quality monitoring stations (p < 0.01,R2 = 0.99; and p < 0.05,R2 = 0.93; respectively). Prediction errors were below 5.1% and 20% respectively. The seasonal pattern of odor perception was associated with the seasonal variation in NH3 concentrations (p < 0.001, adjusted R2 = 0.68).ConclusionThe results suggest that atmospheric NH3 levels at local air quality stations could be used as indicators of prevalence of odor annoyance in non-urban residential communities.

Ammonia and nitric acid dry deposition and throughfall

Since 1991 measurements of fluxes of ammonia have been carried out periodically at a forest location in the western part of Denmark. The ammonia deposition velocities and fluxes are estimated from gradient measurements done by denuders and micrometeorology. The deposition velocities showed a large variation, ranging from deposition mainly governed by the atmospheric transport with fast adsorption at the surface to emission. Nitric acid deposition velocities and fluxes were measured in a period in May 1993 and the data indicate deposition mainly governed by the atmospheric transport and fast adsorption at the surface. The measured ammonia fluxes and an estimate for the particulate ammonium flux are compared to a nine year mean value of the net throughfall from Norway Spruce at the location.