Lars Mølhave

Human reactions to low concentrations of volatile organic compounds

Abstract A group of 62 human subjects were exposed for 2.75 h to a mixture of 22 volatile organic compounds known to be indoor air pollutants. Three total concentrations of 0, 5 and 25 mg/m 3 of the same 22 compounds were used. The subjects were all healthy and without asthma, allergy, or chronic bronchitis but claimed often to suffer from dry mucous membranes in eyes, nose, or upper airways. By using a questionnaire on 26 different air quality aspects, a significant effect of exposure was found for questions related to general air quality, odour, ability to concentrate, and/or mucous membrane irritation. Continuous evaluation of irritation in eyes, nose, and throat showed significant correlation to exposure both at 5 and 25 mg/m 3 . The effect was acute and showed no signs of adaptation. A digit span performance test showed decreased scores during exposure.

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.

Indoor air pollution due to organic gases and vapours of solvents in building materials

The emission of organic gases and vapours of solvent type from 42 commonly used building materials was measured under standard atmospheric conditions. An average of 22 compounds was found in the air around each building material, and the total concentration of gases and vapours was from 0.01 to 1410 mg/m3. The average arithmetic emission rate was 9.5 mg/m2 h, and 52 different compounds were identified. A mathematical model was established for the indoor air concentrations of pollutants originating from building materials. The model was tested on three model rooms constructed from the materials investigated. The calculated total air concentrations of gases and vapours in the three rooms ranged from 1.6 to 23.6 mg/m3, and the number of compounds in the air from 23 to 32. These concentrations and number of compounds did not differ from those found in actual rooms similar in size and construction to the model rooms. The risks of health effects due to the compounds identified from the building materials were investigated, and criteria for future air quality standards are discussed. It is concluded that the possibility of negative health effects cannot be neglected, especially not for the more sensitive minority of the general population.

Exposure of Humans to a Volatile Organic Mixture. II. Sensory

Time-course functions for symptoms of the sick building syndrome were derived from 66 healthy males who, during separate sessions, were exposed to clean air and to a volatile organic compound (VOC) mixture. The mixture contained 22 VOCs (25 mg/m3 total concentration) commonly found airborne in new or recently renovated buildings. Subjects rated the intensity of perceived irritation, odor, and other variables before, and twice during, 2.75-h exposure periods. Eye and throat irritation, headache, and drowsiness increased or showed no evidence of adaptation during exposure, whereas odor intensity decreased by 30%. These results indicate that irritation intensity and other symptoms are not related in any simple way to odor intensity, which suggests that the symptoms may not be a psychosomatic response to the detection of an aversive odor. Instead, subthreshold levels of VOCs may interact additively or hyperadditively and stimulate trigeminal nerve receptors. Also, air quality ratings improved by 18% during exposure, which suggests that both odor and irritation intensity may influence assessments of air quality.

Exposure of humans to a volatile organic mixture. I. Behavioral assessment

Exposure to a low-level mixture of volatile organic compounds, typical of those found in new buildings, has been reported to impair neurobehavioral function in persons who have experienced sick building syndrome (SBS). Sixty-six healthy young males who had no history of chemical sensitivity were exposed for 2.75 h to a complex mixture of volatile organic compounds at 0 and 25 mg/m3. Even though subjects reported more fatigue and more mental confusion following exposure to volatile organic compounds than to clean air, performance on 13 neurobehavioral tests was not affected. Practice or learning effects were observed if administration of many behavioral tests were repeated. Further studies are needed to clarify the relationship of exposure to volatile organic chemicals, neurobehavioral performance, and subject characteristics, e.g., age, gender, and chemical sensitivity.

Human reactions to a mixture of indoor air volatile organic compounds

Abstract A controlled experimental study of human reactions to a mixture of 22 volatile organic compounds often found in indoor air was performed in a climate chamber. Twenty-one healthy subjects were compared with a group of 14 subjects suffering from the ‘sick building syndrome’ (SBS subjects), i.e. having symptoms related to the indoor environment (irritated mucous membranes, headache, etc.) as defined by WHO in 1982. In groups of 4 these subjects were exposed during two successive periods to either 0 and 0 mg m −3 , 25 and 0 mg m −3 , or 0 and 25 mg m −3 ; 25 mg m −3 is equivalent to the highest concentrations expected in a new building. The study was double blinded, and a latin square design was used to balance out effects of day in the week and season. Both groups reacted subjectively to the air reporting worse odor, worse indoor air quality as defined by the subject, and more irritated mucous membranes in eye, throat and nose than in the clean environment. A tendency to a stronger response was seen among the SBS subjects. Objective measures indicated among others an exposure related reduction in lung function among SBS subjects. Both groups had an increased number of polymorphonuclear leucocytes in tear fluid as a result of exposure. This was not seen for nasal secretions. Psychological performance tests indicated an exposure related diminished ability to learn. In conclusion, the experiment indicates that exposure to volatile organic compounds in low concentrations as seen in new houses causes both subjective complaints and objective signs in normal healty subjects; but more so in subjects from the sick building syndrome.

The INDEX Project : executive summary of a European Union project on indoor air pollutants

The prevalence of allergies, asthma and other respiratory diseases in large populations has increased in recent decades. Among other factors, this phenomenon has been connected to adverse health effects of air pollution. Although some causal links between occupational exposures and their health effects are shown, still little is known about the health risks of lifelong exposure to indoor air pollutants. To assess the health risks of indoor air pollutants at prevailing concentration levels in Europe, the Joint Research Centre of the European Commission carried out a project called “Critical Appraisal of the Setting and Implementation of Indoor Exposure Limits in the EU” (INDEX). The aims of the project were: ( 1 ) to assess health risks of indoor‐originated chemical pollutants that might be regulated in the EU and ( 2 ) to provide suggestions and recommendations on potential exposure limits or other risk management measures. The results of the INDEX project should contribute to the development of an EU strategy for the management of indoor air quality. The highest priority was given in this study to: formaldehyde, nitrogen dioxide, carbon monoxide, benzene and naphthalene. Exposure limits, recommendations and management options were also given to minimize the health risks for these compounds.

The sick buildings and other buildings with indoor climate problems

Abstract The Sick Building Syndrome (SBS) is one of many terms used by occupants to describe symptoms of reduced comfort or health related to the indoor atmospheric environment. Many poorly defined synonymous terms, including “the sick buildings,” have been used by different investigators for these buildings. A more systematic grouping of the problem buildings is suggested. A general term, Indoor climate problem building, may be used for any building in which occupants are dissatisfied with the indoor atmospheric environment. The subgroup of problem buildings, in which all atmospheric factors are below the thresholds of their known dose-response relationships is often identified by the term “the sick buildings.” The dose-response relationship in these buildings may be multifactorial. This multifactorial dose-response relationship in these previous definition of the sick building syndrome published by the WHO includes a pattern of symptoms that have been seen repeatedly in indoor climate problem buildings. A more systematic list of symptoms, including those identified in the WHO definition, is suggested. According to this systematic listing, symptoms or effects are classfied into five categories, and a revised definition of the sick building syndrome is expressed in five criteria. This definition of the sick building syndrome and its consequences are discussed.

Neurobehavioral and sensory irritant effects of controlled exposure to a complex mixture of volatile organic compounds

Subjective reactions of discomfort, impaired air quality, irritation of mucosal membranes, and impaired memory have been reported in chemically sensitive subjects during exposure to volatile organic compounds (VOCs) found in new buildings. Sixty-six normal healthy male subjects aged 18-39 were exposed for 2.75 hr to a complex VOC mixture at 0 and 25 mg/m3. Each subject completed control and exposure sessions at one-week intervals in counterbalanced order. Measurements included comfort ratings of eye, nose and throat irritation, symptom questionnaire and computerized behavioral tests. Subjects found the odor of VOCs unpleasantly strong and reported that VOC exposure degraded air quality, increased headache and produced general discomfort. VOC exposure did not affect performance on any behavioral tests.

Subjective reactions to volatile organic compounds as air pollutants

Abstract Human subjective reactions to indoor air pollution in the form of volatile organic compounds in five concentrations ⩽ mg m −3 were examined in a climate chamber under controlled conditions in a balanced experimental design. The reactions of 25 subjects were registered in two questionnaires containing 25 and six questions and on a linear analogue rating scale. Each subject was tested for one day including four runs in each of the five treatments of 50 min duration. Dose effects were found for perceived odour intensity at 3 mgm −3 . Air quality, need for ventilation, irritation of eye and nose showed significant effect at 8 mg m −3 . Significant reduced well being was reported at 25 mgm −3 . The analyses indicated that lower threshold for some of these effects would have been found if more subjects or longer exposure-times had been used. Gender, age, occupational education and smoking habits were co-factors for many of the symptoms reported.