Gunnar R. Lundqvist

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...

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...

Middle ear effusion in children and the indoor environment: an epidemiological study.

A prospective study of 337 children was carried out during a 3-month period. The purpose of the study was to evaluate the importance of indoor environmental factors in homes and day-care institutions for the incidence of middle ear effusion (MEE). The indoor environmental factors measured in institutions were carbon dioxide, temperature, and relative humidity. Conditions in the homes were assessed by a questionnaire. Middle ear effusion was measured by tympanometry. No relationship was found between indoor environmental factors and MEE, with the exception of parental smoking at home, which increased the frequency of MEE in children.

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 response to varying concentrations of toluene

SummaryThirty two males and 39 females aged 31–50 were exposed for 7 h to one of the three following conditions: (1) Clean air, (2) constant exposure to 100 ppm toluene, or (3) a varying exposure with the same time-weighted average, but with peaks of 300 ppm every 30 min. During exposure the subjects exercised in three 15-min periods with a load of 50 to 100 W. Exposure to toluene caused significant (P < 0.05) complaints about poor air quality, altered temperature and noise perception, increased irritation in the nose and the lower airways, feeling of intoxication, and there were tendencies (P < 0.1) towards irritation in the throat, headache and dizziness. In the four performance tests there was a tendency towards a lower score in a vigilance test while no effect of toluene exposure was seen in a peg board test, a five choice serial reaction test, or a colour test, indicating only minimal if any effect on the psychomotor or visual performance. There was no difference in the acute effects caused by the exposure containing peak concentrations and by the constant exposure.

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.

Effect of ethanol, cimetidine and propranolol on toluene metabolism in man

SummaryIn a climatic exposure chamber four healthy volunteers were exposed to 100ppm toluene, 100ppm toluene + ethanol, 100ppm toluene + cimetidine, and 100ppm toluene + propranolol for 7h each at random over four consecutive days. A control experiment and 3.5 h of exposure to 200 ppm toluene were also performed. Ethanol inhibited toluene metabolism by 0.5 as expressed by the urinary excretion of two of the metabolites of toluene, namely o-cresol and hippuric acid. In agreement with this, the mean alveolar concentration of toluene was greater by 1.7 during ethanol exposure; 45 min after discontinuation of exposure the increase was by 3.3. Neither cimetidine nor propranolol changed toluene metabolism significantly. The results indicate that ethanol may prolong the time interval in which toluene is retained in the human body in persons simultaneously exposed to ethanol and toluene. When using o-cresol or hippuric acid in biological monitoring of persons occupationally exposed to toluene, the consumption of ethanol should be considered.

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.

Toluene metabolism during exposure to varying concentrations combined with exercise

SummaryThe urinary excretion of hippuric acid (HA) and ortho-cresol (O-cr) in man was measured in two studies of 7-h exposure to toluene in a climate chamber, either constant concentration of 100 ppm or varying concentrations containing peaks of 300 ppm but with a time-weighted average of 100 ppm. In Study A, four males were exposed to clean air and to constant and varying concentrations of toluene in combination with rest and with 100 W exercise in 140 min. Exercise increased end exposure excretion rate of HA and O-cr by 47 and 114%, respectively. After exposure, all excess HA was excreted within 4 h, while O-cr was eliminated with a half life of about 3 h. Alveolar air concentration of toluene varied between 21 and 31 ppm during constant exposure and between 13 and 57 ppm during varying exposure, but no difference in mean alveolar toluene concentration or in metabolite excretion was seen between the exposure schedules. In Study B, 32 males and 39 females aged between 31 and 50 years were exposed once to either clean air, constant or varying concentrations of toluene. Background excretion rate of HA was 0.97 ± 0.75 mg/min (1.25 ± 1.05 g/g creatinine) and rose to 3.74 ± 1.40 mg/min (3.90 ± 1.85 g/g cr) during the last 3 h of exposure to 100 ppm toluene. The corresponding figures for O-cr were 0.05 ± 0.05 μg/min (0.08 ± 0.14 mg/g cr), and 2.04 ± 0.84 μg/min (2.05 ± 1.18 mg/g cr). The individual creatinine excretion rate was considerably influenced by sex, body weight and smoking habits, thus influencing the metabolite concentration standardised in relation to creatinine. It is concluded that both metabolites are estimates of toluene exposure. O-cr is more specific than HA, but the individual variation in excretion of both metabolites is large, and when implementing either of them as biological exposure indices, the influence of sex, body size, age as well as consumption of tobacco and alcohol has to be considered.