Ib Andersen

Indoor air pollution due to chipboard used as a construction material

Chipboard (particle board) is a common building construction material made of wood-shavings held together with a urea-formaldehyde glue. Due to this composition there is a continuous emanation of formaldehyde from chipboard. Measurements in 25 rooms in 23 Danish dwellings where chipboard was used in walls, floors and ceilings showed that the average concentration was 0.62 and the range 0.08–2.24 mg formaldehyde m−3 air exceeding the German threshold limit for occupational exposure (1.2mg m−3). In all rooms the concentration exceeded the German limit for continuous exposure in outdoor air (0.03 mg m−3). In climate chamber experiments the equilibrium concentration of formaldehyde from chipboard was found to be directly proportional with temperature and water vapour concentration in the air (H g H2O kg−1). A hyperbolic decrease in formaldehyde concentration occurred at increasing ventilation rates. A mathematical model for the room air concentration of formaldehyde has been established. The model is E=(RT+S)(ah+b)1+(ncα)mg HCHO m−3air where a, b, c, S and R are constants depending on type and surface coating of chipboard. T is air temperature °C, n ventilation, air changes h−1 and α area board/room volume, m2 m−3. The constants a, b, c and S were determined on the basis of the chamber measurements, while R has to be calculated for each room from the results of measurements in the room. The model reproduces the measurements in dwellings and in the climate chamber with correlation coefficients of 0.88 and 0.94 respectively in the intervals 17–32°C, 5–13 g H2O kg air−1 and 0.4–3 air changes h−1 and may be used for prediction of formaldehyde concentrations in rooms containing chipboard. The adverse health effects of low levels of formaldehyde are irritation of the upper airways and conjunctivitis. The need for air quality standards and control programmes for indoor air in the home is stressed.

Human response to controlled levels of sulfur dioxide.

Nasal mucus flow rate, airway resistance, and subjective response was studied in 15 young men during six-hour exposures to 1, 5, and 25 ppm sulfur dioxide (SO2). A significant decrease in nasal mucus flow rate during 5- and 25-ppm exposures was observed. This decrease was greatest in the anterior nose and in subjects with an initially slow mucus flow rate. Pharyngeal air samples yielded less than 1% of the SO2 inhaled, even after a six-hour exposure to 25 ppm SO2. An increased nasal airflow resistance and a fall in forced expiratory volume in one second and forced expiratory flow during the middle half of expired volume was found at all exposure levels, but there was no change in “closing volume.” Discomfort was proportional to SO2 concentration, but never excessive. Subjects with initially slow nasal mucus flow rates experienced the greatest discomfort. The acute effects of SO2 exposure appear to justify reduction of the present threshold limit value of 5 ppm to 1 ppm, and provide support for a nasobronc...

A Comparison of Nasal and Tracheobronchial Clearance

Tracheobronchial clearance and nasal clearance were compared in 13 pairs of monozygotic twins and 11 nontwins. Tracheobronchial clearance was studied by having the subjects inhale, by mouth, a test aerosol of 6μmol particles tagged with technetium Tc 99m (99mTc) and making external measurements of the radioactivity. Nasal clearance was studied with two methods: (1) a 0.6-mm anion resin particle tagged with 99mTc was externally followed at five different points along the nasal passage and (2) a saccharine particle was placed on the mucociliary mucosa anteriorly in the nose and the time was registered until the subject noted a sweet taste. A weak positive association existed between tracheobronchial clearance and nasal clearance as studied with the saccharine particle method, but no association was found between tracheobronchial clearance and nasal clearance as tested by the tagged resin particle method.

Human Response to 78-Hour Exposure to Dry Air

We studied the effects of dry air on nasal mucus flow rate, nasal resistance, forced vital capacity, skin resistance, and discomfort in eight young healthy men exposed to clean air at 23 C in a climate chamber. After 27 hours at 50% relative humidity (RH) they lived for 78 hours at 9% RH and then returned to the initial level of 50% RH for 20 hours. No significant changes were observed in the nasal mucus flow rate throughout the experiment. Nor did a tenfold increase in nasal respiration during 20-minute periods of exercise in the dry air cause any change in mucus flow rate. No changes were observed in nasal or tracheobronchial resistance except for a 58% increase in calculated cross-sectional nasal area during exercise. The humidity voting for the subjects varied widely and related poorly to the humidity conditions; the average votings always were in the comfort range. No discomfort was reported from the body surfaces, and skin resistance did not change. The study indicates that there is no physiological...

Relationships between outdoor and indoor air pollution

Abstract Paired 24-h samples of sulphur dioxide and suspended particulate matter were studied outside and inside a room for 7 1 2 months. The indoor concentrations of sulphur dioxide and suspended particulate matter were, on average, 51 and 69 per cent respectively of the simultaneous outdoor values. For the two pollutants the coefficients of correlation between indoor and outdoor values were 0.52 and 0.83 respectively. The factors which determine the concentration-level of a pollutant in a room are expounded, and stress is laid on the medicalhygienic importance of increasing the effects of building materials in reducing pollution.

Human Nasal Mucosal

We have measured nasal mucociliary transport rates once in 58 subjects and, in 22 of these, three additional times at intervals of two hours. The study was performed under controlled climatic conditions (with a temperature of 23 C and relative humidity of 68%). The subjects could be classified in three groups: 32 who had a rapid uninterrupted particle movement, 14 who had a stop or slowdown in particle movement after an initial normal flow, and 10 who had either a constantly slow particle movement or stasis during the experiment. The transport rates in the first group ranged from 0.23 to 2.36 cm min-1, with an average of 0.84 cm min-1. In the subjects studied four times at two-hour intervals, some exhibited marked changes in transport rates during the eight-hour day.

Human nasal mucosal function at controlled temperatures.

We exposed 16 healthy human volunteers to air temperatures ranging from 7 to 39 degrees C and measured nasal mucus flow, nasal airflow resistance, forced vital capacity, rectal and body surface temperature, and air temperature within the nasal passage. A moderate fall in nasal mucus flow rate in the anterior and middle parts of the nose was observed with temperature above or below 23 degrees C. The nasal airflow resistance decreased in warm air and tended to increase in cold air. No significant changes in forced vital capacities or rectal temperature were observed. Nasopharyngeal end inspiratory air temperatures at 23 degrees C averaged 32.6 degrees C. At environmental temperatures of 15 and 31 degrees C they average 28.1 and 32.8 degrees C, respectively. Although we found alterations in upper airway function associated with altered inspired air temperature, over the range of 32 degrees C studied these changes were of minor physiological significance.

Human Perception, of Humidity Under Four Controlled Conditions

We have studied the subjective perception of humidity and temperature in 48 young male subjects exposed to clean air at 23 C with a relative humidity CRH) of 70%, 50%, 30%, and 10%. We observed no change in the perception of humidity on lowering it from 70% to either 50%, 30%, or 10%, nor on returning it to the initial level of 70%. The decrease and rise in RH did cause highly significant changes in the subjective sensation of temperature although this factor was held constant throughout.