Indoor air quality assessment of daycare facilities with carbon dioxide temperature, and humidity as indicators. (Features).

Introduction

Today, over 50 percent of mothers whose youngest children are under the age of six are in the workplace (Hofferth & Phillips, 1987; Strauman-Raymond, Lie, & Kempf-Berkesth, 1993). A large number of American children are being taken care of inside daycare settings. Research studies indicate, however, that child daycare service environments can be hazardous places for young children because of indoor air quality (IAQ) problems (Daneault, Beausoleil, & Messing, 1992). Since young children differ from older age groups in terms of physical structures and functioning--their lungs are still developing, as are their immune and central nervous systems, and they have higher respiratory rates and rates of physical activity--they are more vulnerable to indoor air pollutants (Miller, 1993). Thus, appropriate indoor environment in daycare centers and homes has become a public focus.

It has been found that ventilation is inadequate in many daycare services, especially those built in the 1970s (Gursky, 1991). Research also has shown that daycare providers are aware of the IAQ issues in their facilities but that many have decided not to address the issue because they believe assessing and correcting IAQ problems is not their responsibility (LaFollette, Hobson, & Crank, 2000). These results alert us to potential problems that may adversely affect the health of many young children.

The commonly seen indoor air pollutants are gases and vapors such as carbon monoxide (GO), carbon dioxide ([CO.sub.2]), formaldehyde (HCHO), other volatile organic compounds (VOCs), and oxides of nitrogen (NO and [NO.sub.2]), as well as radon, particles from biological aerosols (fungi, mold spores, pollen, insect parts, and feces), asbestos fiber, and tobacco smoke. Excessive [CO.sub.2] exposure can cause headaches, tiredness, and decrease in mental acuteness, and it increases the risk of sudden infant death (Corbyn, 1992). Studies also have demonstrated that the relationship between [CO.sub.2] concentrations and IAQ evaluation is relatively distinct (Rajhans, 1985; Yocom & McCarthy, 1991; Daneault et al., 1992; Olesen & Seelen, 1993; Haghighat & Donnini, 1993). American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) standard sets 2,500 parts per million (ppm) as the upper limit for indoor [CO.sub.2] concentration, but 1,000 ppm is the recommended maximum. Temperature and relative humidity were also used to determine the comfort level of the indoor environment at daycare facilities (ASHRAE, 1989).

Concerned about the IAQ young children are exposed to, the authors of this study evaluated the current IAQ status of licensed daycare facilities in a Midwestern county of the United States.

Methods

Selection of Participants

Participants were randomly selected from a total of 122 licensed daycare centers and homes listed in a Midwestern county of the United States. A letter explaining the purpose of the study was sent to the providers of the selected daycare centers and homes requesting their participation. A follow-up phone call was made if they did not respond to the first request. A total of 26 daycare providers agreed to participate in the study. The participants comprised 16 daycare centers and 10 daycare homes. The overall participation rate was 21.3 percent; response rates from daycare centers and homes were 94.1 percent and 9.5 percent, respectively A daycare home is defined as a private dwelling for the care of children under 11 years of age. A daycare center is defined as any institution designed for the purpose of providing care or maintenance for children less than six years of age (Indiana State Department of Public Welfare, 1992).

Indoor Air Quality Measurement

[CO.sub.2] concentration, temperature, and relative humidity are commonly used as indicators of indoor air quality and comfort level because they are convenient and reliable (Daneault et al., 1992; Kiefer, Van Gilder, & Decker, 1993). Both indoor and outdoor [CO.sub.2] concentrations, temperature, and relative humidity were collected for comparison (Kiefer et al.). Indoor air quality was measured in 26 daycare facilities during non-nap-time periods from 7:30 a.m. to 3:30 p.m. Nap-time indoor air measurements were taken in the 23 daycare facilities that had nap-time activity All parameters were measured once for each daycare facility in the same day To assess variation in indoor air quality throughout the day, the intervals of the measurements during non-nap time and nap time were set at every 30 minutes and every five minutes, respectively, in each room. Moreover, in order to understand the change in IAQ from before to after occupancy background [CO.sub.2] temperature, and relative humidity were measured in the 26 daycare facilities before people arrived. Real-time [CO.sub.2] concentration, temperature, and humidity were measured with a direct-reading instrument (TSI QTRAK IAQ Monitor Model 8550), which was calibrated before each measurement.

Data Analysis

All obtained data were analyzed with the Statistical Package for Social Science (SPSS) program. The means [+ or -] standard deviation (SD) of [CO.sub.2], room temperature, and relative-humidity levels were calculated to give the IAQ of the daycare facilities. Paired t-tests were applied to measure the differences in IAQ parameter averages between non-nap time and nap time. One-way analysis of variance (ANOVA) was used to analyze the difference in IAQ parameters in different types of facilities, different rooms, and different time periods. The statistical significance level was set at .05. A stepwise multiple regression analysis was used to establish the relationship between [CO.sub.2] levels and other variables.

Results

There was no significant difference between the IAQ in daycare centers and that in homes; therefore, all the data were combined, analyzed, and presented as daycare IAQ.

Temperature

The average room temperature for the 26 daycare facilities was 73.7 [+ or -] 2.9[degrees]F. Forty-two percent of daycare facilities were out of the comfort zone (73[degrees]F-79[degrees]F) recommended by ASHRAE; the majority of those (34.6 percent) had temperatures lower than 73[degrees]F. The variation in room temperature during different activities was within 1[degrees]F. The distribution of average daytime room temperature across facilities and activities is shown in Figure 1.

Relative Humidity

The average relative humidity of the 26 daycare facilities was 50.2 [+ or -] 8.7 percent. Eighty-four percent of the facilities had relative humidity between 30 percent and 60 percent, which is the comfort zone recommended by ASHRAE. None of the facilities had relative humidity below 30 percent. The variation in relative humidity during different activities was not significant (within 1.3 percent). The data did show, however, that more daycare facilities (26.1 percent) exceed the recommended comfort zone during nap time than during non-nap time. The distribution of the relative humidity across facilities and activities is shown in Figure 2.

Carbon Dioxide

The average [CO.sub.2] level for all 26 daycare facilities was 1,142.4 [+ or -] 473.6 ppm. In more than half of the facilities (53.9 percent), [CO.sub.2] levels exceeded the ASHRAE-recommended standard of 1,000 ppm; 3.9 percent of the facilities even had levels over ASHRAE's tolerance maximum of 2,500 ppm (Figure 3). The average nap-time [CO.sub.2] level was noticeably higher than the average non-nap-time level (the difference was 104.8 [+ or -] 287.3 ppm); however, the difference is not statistically significant (p = 0.094).

Nap-time measurements were made for a total of 31 rooms. Twenty-four rooms were defined as multipurpose rooms (for general activities and nap). Seven rooms were sleeping-only rooms (designated for nap only). In multipurpose rooms, the average [CO.sub.2] levels for non-nap time and nap time were 1,262.6 [+ or -] 606.1 ppm and 1,308.7 [+ or -] 649.0 ppm, respectively. The median [CO.sub.2] increment from non-nap time to nap time was 13.6 percent. In multipurpose rooms, the change in [CO.sub.2] level from non-nap time to nap time was not statistically significant (p = 0.5). For sleeping-only rooms, by contrast, the non-nap-time average [CO.sub.2] level of 915.1 [+ or -] 203.9 ppm was statistically different from the nap-time average [CO.sub.2] level of 1,228.1 [+ or -] 429.8 ppm (p = .021). The median [CO.sub.2] increment from non-nap time to nap time was 24.3 percent. With KruskalWallis one-way ANOVA, there was a statistically significant difference between the [CO.sub.2] increment in multipurpose rooms and the increment in sleeping-only rooms (p = .006). The increase in [CO.sub.2] level from non-nap time to nap time in a sleeping-only room was higher than that in a multipurpose room.

Predictions for Non-Nap-Time Average [CO.sub.2] Level

For non-nap-time average [CO.sub.2], only one independent variable, average background [CO.sub.2] level, could significantly predict [CO.sub.2] level. The result showed that for each increase of 1 ppm in background [CO.sub.2], the level of non-naptime average [CO.sub.2] increased by 1.08 ppm. Table 1 gives the result of stepwise multiple regression analysis for non-nap time.

Predictions for Nap-Time Average [CO.sub.2] Level

Four independent variables--background [CO.sub.2] level, nap-time average temperature, naptime average carbon monoxide (CO), and nap-time average child density-were significant predictors of nap-time average [CO.sub.2] level. The results of a stepwise multiple regression analysis are summarized in Table 2.

Discussion

This research project accessed IAQ indicators from 26 licensed daycare facilities in a Midwestern county during spring 1996. It was found that 7.7 percent of the facilities had room temperatures above the recommended comfort zones, compared with 8.0 percent found in a Canadian study of daycare IAQ (Daneault et al., 1992). Overheating should be avoided, since overheated children easily relax into daydreaming and abandon efforts at mental concentration (Wilson, 1969). With respect to relative humidity, 15.4 percent of the facilities exceed the recommended comfort zone (i.e., relative humidity exceeded 60 percent). By comparison, 17 percent of the facilities in the Canadian study fell outside the humidity comfort range, defined in that study as 30 to 55 percent humidity (Daneault et al.). It is expected that some health problems and material damages can occur when the relative humidity exceeds the critical value of 60 percent (Wanner, 1993).

[CO.sub.2] commonly has been used as an indicator of indoor air quality, and it also has served as the determiner for adequate ventilation in general (ASHRAE, 1989; Rajhans, 1985). In addition, [CO.sub.2] has been related to various symptoms, such as headaches, dry throat, skin dryness, tiredness, and decrease in mental acuteness (ASHRAE, 1989; Daneault et al., 1992). Exposure to excessive concentrations of [CO.sub.2] increases the risk of sudden infant death (Corbyn, 1992). In this study, [CO.sub.2] measurements found that levels in over 50 percent of daycare facilities exceeded 1,000 ppm during the daytime and that in 3.9 percent the levels were over 2,500 ppm. It was observed that the nap-time average [CO.sub.2] level was about 104 ppm higher than the non-nap-time average [CO.sub.2] level. The increment in [CO.sub.2] level at nap time might have resulted from the fact that all the children were placed in a closed space without proper ventilation. This situation arose frequently in every room during nap ti me, especially in those rooms used only for the purpose of nap-time sleeping. In fact, statistical tests suggested that both concentration increment and percentage increment in average [CO.sub.2] level from non-nap time to nap time in sleeping-only rooms were statistically greater than they were in multipurpose rooms (p < .05).

Moreover, in this study, multiple regression analysis showed that background [CO.sub.2], nap-time average temperature level, naptime average CO level, and nap-time average child density were significantly related to nap-time average [CO.sub.2] levels ([R.sup.2] - .83). Background [CO.sub.2] concentrations might be retained in spaces and relate to the readings of average [CO.sub.2] levels during non-nap time and nap time.

It was observed that nap-time average [CO.sub.2] level was significantly adversely related to nap-time average temperature level (p = .00). A look at the types of ventilation systems installed in daycare facilities might be able to explain the phenomenon. Most daycare facilities had ventilation systems with thermostats. Ventilation systems were automatically turned on when temperature increased during nap time. Consequently, the [CO.sub.2] accumulation would be reduced. Although CO was significantly related to nap-time [CO.sub.2] levels, it was hard to find any evidence that the existence of CO could raise the nap-time average [CO.sub.2] level. [CO.sub.2] was a main product of human respiration; people typically generate 0.3 liters per minute of [CO.sub.2] at rest (Yocom & MacCarthy, 1991). Therefore, the child density was related, as expected, to nap-time average [CO.sub.2] level (p = .00). In the Canadian study, however, four variables were significantly related to the average [CO.sub.2] levels. They were density of children, use of a heating system, presence of artificial ventilation, and the age of building (Daneault et al., 1992).

Conclusion and Recommendations

The indoor air quality of licensed daycare facilities affects not only the health of children attending facilities, but also that of the workers. According to ASHRAE Standard 1989, immediate action would be recommended if the [CO.sub.2] levels, room temperature levels, and some humidity levels were outside the ranges described in this study The suggested limit for an eight-hour exposure of [CO.sub.2] is 1,000 ppm (ASHRAE, 1989). The OSHA eight-hour time-weighted-average (TWA) permissible-exposure limit (PEL) is 5,000 ppm. (29 CFR 1910.1000). Until now, no IAQ standard has been developed specifically for occupants of daycare facilities. Such a standard is desperately needed for young children, as they are more vulnerable than adults to poor indoor air quality (Gratz & Boulton, 1993).

The nap-time increment in average [CO.sub.2] level was higher in sleeping-only rooms than in multipurpose rooms. This finding could be due to the fact that the daycare facilities placed all the children in a closed space without proper ventilation. Minor air currents from windows and doors that bring fresh air are needed for sleeping children (Corbyn, 1992), and natural air exchange from an open window or door is helpful in reducing the accumulations of [CO.sub.2] and other hazardous indoor air pollutants. It is an effective way to lower the nap-time [CO.sub.2] concentration in sleeping-only rooms. Installation of a more efficient ventilation system is also recommended for improving indoor air quality Moreover, routine inspection and maintenance must be carried out to ensure that ventilation systems are operating properly.

The authors hope that results of this assessment have informed managers of daycare facilities in the surveyed area of their current IAQ status and have encouraged them to improve the indoor air in their facilities.

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TABLE 1

Prediction of [CO.sub.2] Level During Non-Nap Time from Stepwise
Multiple Regression Analhysis (a)

Independent Variables        Step of Entry  [beta] (SD)  Constant

Background [CO.sub.2] (ppm)        1        1.08 (0.93)   205.16


Independent Variables          [R.sup.2] Change

Background [CO.sub.2] (ppm)          0.87
                             Total [R.sup.2]:0.87

(a)Variables used not retained in the regression analysis: type of
facility, type of room, use of ventilation, background CO, temperature,
relative humidity, non-nap-time child density, non- nap-time average CO,
temperature, and relative humidity.
TABLE 2

Prediction of [CO.sub.2] Level During Nap Time from Stepwise Multiple
Regression Analysis (a)

Independent Variables                      Step of Entry   [beta] (SD)

Background [CO.sub.2] (ppm)                      1          0.64 (0.52)
Nap-time average temperature ([degrees]F)        2        -95.29 (-0.47)
Nap-time average CO (ppm)                        3        342.78 (0.47)
Nap-time average child density                   4        104.11 (0.26)
 (per 1,000 [ft.sup.3])


Independent Variables                      Constant

Background [CO.sub.2] (ppm)                6,934.25
Nap-time average temperature ([degrees]F)
Nap-time average CO (ppm)
Nap-time average child density
 (per 1,000 [ft.sup.3])


Independent Variables                        [R.sup.2] Change

Background [CO.sub.2] (ppm)                        0.65
Nap-time average temperature ([degrees]F)          0.06
Nap-time average CO (ppm)                          0.06
Nap-time average child density                     0.06
 (per 1,000 [ft.sup.3])
                                           Total [R.sup.2]:0.83

(a)Variables used but not retained in the regression analysis: type of
facility, type of room, use of ventilation, background CO, temperature,
and relative humidity.

Acknowledgement: The authors appreciate the assistance of Dr. Jake Jakaitis in manuscript preparation, as well as research funding from Indiana State University.

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Corresponding Author: Shiaw-Fen Ferng, Professor, Department of Health and Safety, Indiana State University, Terre Haute, IN 47809. E-mail: <[e-mail]>.