Jørn Toftum

Extension of the PMV model to non-air-conditioned buildings in warm climates

Abstract The PMV model agrees well with high-quality field studies in buildings with HVAC systems, situated in cold, temperate and warm climates, studied during both summer and winter. In non-air-conditioned buildings in warm climates, occupants may sense the warmth as being less severe than the PMV predicts. The main reason is low expectations, but a metabolic rate that is estimated too high can also contribute to explaining the difference. An extension of the PMV model that includes an expectancy factor is introduced for use in non-air-conditioned buildings in warm climates. The extended PMV model agrees well with quality field studies in non-air-conditioned buildings of three continents.

Upper limits of air humidity for preventing warm respiratory discomfort

Abstract The effect of humidity and temperature of inhaled air on perceived acceptability of the air was studied. Thirty-eight subjects evaluated air at 14 combinations of temperature and humidity to verify that insufficient evaporative and convective cooling of the mucous membranes in the upper respiratory tract is a cause of local warm discomfort and of a perception of poor air quality. Unpolluted, conditioned air was led from a climate chamber to a box where the subjects one by one evaluated the air. The inhaled air was rated warmer, more stuffy and less acceptable with increasing air humidity and temperature. A model was developed that predicts the percentage of persons dissatisfied due to insufficient respiratory cooling as a function of the actual evaporative and convective cooling of the respiratory tract. Together with a previously proposed model for predicting discomfort due to high skin humidity, the respiratory model may be used to specify upper limits for humidity in the indoor environment.

Children's Phthalate Intakes and Resultant Cumulative Exposures Estimated from Urine Compared with Estimates from Dust Ingestion, Inhalation and Dermal Absorption in Their Homes and Daycare Centers

Total daily intakes of diethyl phthalate (DEP), di(n-butyl) phthalate (DnBP), di(isobutyl) phthalate (DiBP), butyl benzyl phthalate (BBzP) and di(2-ethylhexyl) phthalate (DEHP) were calculated from phthalate metabolite levels measured in the urine of 431 Danish children between 3 and 6 years of age. For each child the intake attributable to exposures in the indoor environment via dust ingestion, inhalation and dermal absorption were estimated from the phthalate levels in the dust collected from the child’s home and daycare center. Based on the urine samples, DEHP had the highest total daily intake (median: 4.42 µg/d/kg-bw) and BBzP the lowest (median: 0.49 µg/d/kg-bw). For DEP, DnBP and DiBP, exposures to air and dust in the indoor environment accounted for approximately 100%, 15% and 50% of the total intake, respectively, with dermal absorption from the gas-phase being the major exposure pathway. More than 90% of the total intake of BBzP and DEHP came from sources other than indoor air and dust. Daily intake of DnBP and DiBP from all exposure pathways, based on levels of metabolites in urine samples, exceeded the Tolerable Daily Intake (TDI) for 22 and 23 children, respectively. Indoor exposures resulted in an average daily DiBP intake that exceeded the TDI for 14 children. Using the concept of relative cumulative Tolerable Daily Intake (TDIcum), which is applicable for phthalates that have established TDIs based on the same health endpoint, we examined the cumulative total exposure to DnBP, DiBP and DEHP from all pathways; it exceeded the tolerable levels for 30% of the children. From the three indoor pathways alone, several children had a cumulative intake that exceeded TDIcum. Exposures to phthalates present in the air and dust indoors meaningfully contribute to a child’s total intake of certain phthalates. Such exposures, by themselves, may lead to intakes exceeding current limit values.

Differences between young adults and elderly in thermal comfort, productivity, and thermal physiology in response to a moderate temperature drift and a steady-state condition.

UNLABELLED Results from naturally ventilated buildings show that allowing the indoor temperature to drift does not necessarily result in thermal discomfort and may allow for a reduction in energy use. However, for stationary conditions, several studies indicate that the thermal neutral temperature and optimum thermal condition differ between young adults and elderly. There is a lack of studies that describe the effect of aging on thermal comfort and productivity during a moderate temperature drift. In this study, the effect of a moderate temperature drift on physiological responses, thermal comfort, and productivity of eight young adults (age 22-25 year) and eight older subjects (age 67-73 year) was investigated. They were exposed to two different conditions: S1-a control condition; constant temperature of 21.5 degrees C; duration: 8 h; and S2-a transient condition; temperature range: 17-25 degrees C, duration: 8 h, temperature drift: first 4 h: +2 K/h, last 4 h: -2 K/h. The results indicate that thermal sensation of the elderly was, in general, 0.5 scale units lower in comparison with their younger counterparts. Furthermore, the elderly showed more distal vasoconstriction during both conditions. Nevertheless, TS of the elderly was related to air temperature only, while TS of the younger adults also was related to skin temperature. During the constant temperature session, the elderly preferred a higher temperature in comparison with the young adults. PRACTICAL IMPLICATIONS Because the stock of fossil fuels is limited, energy savings play an important role. Thermal comfort is one of the most important performance indicators to successfully apply measures to reduce the energy need in buildings. Allowing drifts in indoor temperature is one of the options to reduce the energy demand. This study contributes to the knowledge concerning the effects of a moderate temperature drift and the age of the inhabitants on their thermal comfort.

Upper limits for indoor air humidity to avoid uncomfortably humid skin

The hypothesis that skin humidity in itself could be a cause of discomfort was tested with forty persons exposed to five levels of skin humidity. In addition, the effect of fabric material against the skin (cotton versus polyester) and of environmental temperature/clothing insulation on perceived discomfort was studied at one high level of skin humidity. Under all experimental conditions, skin humidity was controlled by the combination of vapor permeability of the experimental clothing ensemble and the thermal environment. The subjects perceived the condition of their skin to be less acceptable with increasing skin humidity at thermal neutrality. No effect of clothing material against the skin or of environmental temperature/clothing insulation was observed. A model was developed that predicts the percentage of persons dissatisfied due to humid skin as a function of the relative humidity of the skin. Existing models of heat and mass transfer can predict the relative skin humidity from thermal environmental parameters, clothing and activity. The new skin humidity model applies for sedentary, thermally neutral persons. The model was used to specify upper limits for indoor air humidity required to avoid discomfort caused by skin humidity. The model predicts that the relative air humidity may be close to 100% without causing much discomfort from humid skin among thermally neutral persons performing sedentary work.

Transdermal uptake of diethyl phthalate and di(n-butyl) phthalate directly from air: Experimental verification

Background Fundamental considerations indicate that, for certain phthalate esters, dermal absorption from air is an uptake pathway that is comparable to or greater than inhalation. Yet this pathway has not been experimentally evaluated and has been largely overlooked when assessing uptake of phthalate esters. Objectives This study investigated transdermal uptake, directly from air, of diethyl phthalate (DEP) and di(n-butyl) phthalate (DnBP) in humans. Methods In a series of experiments, six human participants were exposed for 6 hr in a chamber containing deliberately elevated air concentrations of DEP and DnBP. The participants either wore a hood and breathed air with phthalate concentrations substantially below those in the chamber or did not wear a hood and breathed chamber air. All urinations were collected from initiation of exposure until 54 hr later. Metabolites of DEP and DnBP were measured in these samples and extrapolated to parent phthalate intakes, corrected for background and hood air exposures. Results For DEP, the median dermal uptake directly from air was 4.0 μg/(μg/m3 in air) compared with an inhalation intake of 3.8 μg/(μg/m3 in air). For DnBP, the median dermal uptake from air was 3.1 μg/(μg/m3 in air) compared with an inhalation intake of 3.9 μg/(μg/m3 in air). Conclusions This study shows that dermal uptake directly from air can be a meaningful exposure pathway for DEP and DnBP. For other semivolatile organic compounds (SVOCs) whose molecular weight and lipid/air partition coefficient are in the appropriate range, direct absorption from air is also anticipated to be significant. Citation Weschler CJ, Bekö G, Koch HM, Salthammer T, Schripp T, Toftum J, Clausen G. 2015. Transdermal uptake of diethyl phthalate and di(n-butyl) phthalate directly from air: experimental verification. Environ Health Perspect 123:928–934; http://dx.doi.org/10.1289/ehp.1409151

Draught sensitivity is influenced by general thermal sensation

Abstract The effect of a cool thermal sensation on local discomfort due to draught was studied in a series of human subject experiments. While performing standing arm work, ten male subjects were exposed to mean air velocities increased step-by-step ranging from 0.05 m · s −1 to 0.40 m · s −1 at air temperatures of 11°C and 17°C. Two different levels of thermal sensation between slightly cool and neutral were scheduled. At each level of air velocity, the subjects were asked whether they could feel an air movement, whether it was uncomfortable and where it was felt. Most frequently, draught was felt at the head region comprising face, neck and upper back. The subjective responses showed that significantly more persons feeling slightly cool perceived air movements as uncomfortable than persons having a thermal sensation closer to neutral, provided the air velocity was the same. A relationship was established that specifies the relative increase in the percentage of dissatisfied due to draught at a cool thermal sensation in proportion to a neutral thermal sensation at equal mean air velocity.

Ultrafine Particles: Exposure and Source Apportionment in 56 Danish Homes

Particle number (PN) concentrations (10-300 nm in size) were continuously measured over a period of ~45 h in 56 residences of nonsmokers in Copenhagen, Denmark. The highest concentrations were measured when occupants were present and awake (geometric mean, GM: 22.3 × 10(3) cm(-3)), the lowest when the homes were vacant (GM: 6.1 × 10(3) cm(-3)) or the occupants were asleep (GM: 5.1 × 10(3) cm(-3)). Diary entries regarding occupancy and particle related activities were used to identify source events and apportion the daily integrated exposure among sources. Source events clearly resulted in increased PN concentrations and decreased average particle diameter. For a given event, elevated particle concentrations persisted for several hours after the emission of fresh particles ceased. The residential daily integrated PN exposure in the 56 homes ranged between 37 × 10(3) and 6.0 × 10(6) particles per cm(3)·h/day (GM: 3.3 × 10(5) cm(-3)·h/day). On average, ~90% of this exposure occurred outside of the period from midnight to 6 a.m. Source events, especially candle burning, cooking, toasting, and unknown activities, were responsible on average for ~65% of the residential integrated exposure (51% without the unknown activities). Candle burning occurred in half of the homes where, on average, it was responsible for almost 60% of the integrated exposure.

Human response to combined indoor environment exposures

Most thermal comfort standards and guidelines presume sedentary, light activity and a neutral overall thermal sensation when predicting local thermal discomfort. In addition, current standards specify criteria for separate aspects of the indoor environment, e.g. thermal climate, air quality or noise, with only little consideration of possible interactions between the different types of exposure. The studies summarized in this article found a clear impact of activity and overall thermal sensation on human sensitivity to air movement, whereas no interaction effects of exposure to several local thermal discomfort factors were observed. Limited evidence was found of significant interactions between different aspects of the indoor environment. Only for the effect of air temperature and air humidity on sensory air quality were well-established relationships available.

Role of clothing in both accelerating and impeding dermal absorption of airborne SVOCs

To assess the influence of clothing on dermal uptake of semi-volatile organic compounds (SVOCs), we measured uptake of selected airborne phthalates for an individual wearing clean clothes or air-exposed clothes and compared these results with dermal uptake for bare-skinned individuals under otherwise identical experimental conditions. Using a breathing hood to isolate dermal from inhalation uptake, we measured urinary metabolites of diethylphthalate (DEP) and di-n-butylphthalate (DnBP) from an individual exposed to known concentrations of these compounds for 6 h in an experimental chamber. The individual wore either clean (fresh) cotton clothes or cotton clothes that had been exposed to the same chamber air concentrations for 9 days. For a 6-h exposure, the net amounts of DEP and DnBP absorbed when wearing fresh clothes were, respectively, 0.017 and 0.007 μg/kg/(μg/m3); for exposed clothes the results were 0.178 and 0.261 μg/kg/(μg/m3), respectively (values normalized by air concentration and body mass). When compared against the average results for bare-skinned participants, clean clothes were protective, whereas exposed clothes increased dermal uptake for DEP and DnBP by factors of 3.3 and 6.5, respectively. Even for non-occupational environments, wearing clothing that has adsorbed/absorbed indoor air pollutants can increase dermal uptake of SVOCs by substantial amounts relative to bare skin.