Volatile and Semi-Volatile Organic Compounds
Volatile and Semi-Volatile Organic Compounds in Schools
For a general discussion of indoor volatile organic compounds (VOCs), see the section of this website on VOCs and health. VOCs are present in indoor and outdoor air. Indoor VOCs come from a large number of indoor sources including building materials, furnishings, consumer products, tobacco smoking, people and their activities, and indoor chemical reactions. VOCs from attached buildings such as garages may also enter indoor living spaces. Outdoor air is also a source of indoor VOCs. Indoor air typically contains many VOCs, but most are present at low concentrations. Concentrations of VOCs are often reported in units of micrograms per cubic meter (µg m-3) or parts per billion (ppb). VOCs may be odorous and some VOCs are known or suspected to cause a variety of adverse health effects. Formaldehyde is one of the most common indoor VOCs found at concentrations of potential concern to health. The total volatile organic compound (TVOC) concentration is a measure of the total concentration of all measured VOCs. TVOC concentrations have not been demonstrated to be a consistently useful predictor of adverse health effects. Semi-volatile organic compounds (SVOCS) are chemically similar to other VOCs with carbon-based molecular structures but are present both as a gas and, to a substantial degree, sorbed (stuck) to indoor materials and the surfaces of airborne particles. Flame retardants, plasticizers, and pesticides are examples of the indoor sources of SVOCs.
Concentrations of VOCs in schools are available from numerous, generally small, surveys of a few to a few tens of classrooms. Fewer data are available on concentrations of SVOCs in classrooms. Table 1 below summarizes key findings. As in other types of buildings, classroom research indicates that the concentrations of many VOCs are much higher indoors than outdoors, indicating the presence of indoor VOC sources [1-7]. Measured concentrations of VOCs vary widely among locations within schools, among schools in the same study, and among studies or study locations. Among the measured VOCs, formaldehyde concentrations were usually highest, tens of ìg m-3, relative to other VOCs typically with concentrations less than 10 ìg m-3, and sometimes less than 1.0 ìg m-3. Concentrations of terpenes were also sometimes higher than concentrations of many other VOCs [2, 3, 8]. Cleaning products are often a predominate source of terpenes. Concentrations of VOCs in schools were typically less than concentrations reported from measurements in homes [9]. A study of sources of VOCs, excluding formaldehyde, in Australian schools [4] estimated that 41% of indoor VOCs were attributable to cleaning products, 23% were attributable to air fresheners, and 21% were attributable to arts and crafts materials. Emissions from building materials were a minor source.
Few studies have assessed associations of VOC concentrations in schools with health outcomes. Four of the studies listed in Table 1 [10-14] below include investigations of potential respiratory health effects of higher formaldehyde concentrations in schools. Two of the four studies [10, 12] report statistically significant increases in health effects with increased classroom formaldehyde. In a large cross sectional study in 108 French schools [10], higher indoor concentrations of formaldehyde (median was about 27 µg m-3) were statistically significantly associated with increased rhinoconjunctivitis (nasal congestion, runny nose, red or irritated eyes); however, higher formaldehyde was not associated with past year asthma or past year allergic asthma. In a study of 28 classrooms from 11 secondary schools in Sweden [12], formaldehyde concentrations were generally low (mean less than 5 µg m-3); however, there was a statistically significant increase in rates of current asthma in classrooms with higher formaldehyde concentrations. In another of the four studies [11], this one of 30 classrooms in China, there were increases in airway symptoms and asthma outcomes in classrooms with higher formaldehyde concentrations; however, the increases were not statistically significant. The fourth study [13] found no association of classroom formaldehyde with respiratory symptoms.
For other VOCs, findings are even more limited. One study [10] found statistically significant associations of higher indoor concentrations of acrolein with increases in past year asthma and past year allergic asthma, but not with rhinoconjunctivitis (nasal and eye symptoms). Combustion is usually the dominant source of acrolein, with cooking a potential source in schools. The same study found no associations of classroom acetaldehyde concentrations with health effects. Three studies report statistically significant associations of higher TVOC concentrations with respiratory health effects. Norback et al. [15] found higher classroom TVOC concentrations associated with statistically significant increases in chronic sick building syndrome (SBS) symptoms but not with development of new SBS symptoms. Smedge et al. [12] found higher TVOC concentrations at school associated with current asthma. A study of 76 classrooms from 11 schools in Portugal [14] found statistically significant increases in sick building syndrome symptoms within teachers associated with higher TVOC levels. It appears that there was no control for potential confounders; thus, in this study higher TVOC levels could have served as a proxy for some other exposure or factor causally related to increased symptoms. A single study [13] found higher concentrations of Texanol, a common component of paints, associated with increased nocturnal breathlessness. The same study found higher concentrations of TXIB, a common plasticizer in PVC floor coverings, associated with increases in nocturnal and daytime breathlessness, doctor diagnosed asthma, and current asthma. All of the associations were statistically significant.
One study [16] investigated associations of SVOCs in floor dust, and in particles from air samples, with student cognitive performance. There were statistically significant associations of higher concentrations of tris (2-chlorethylphosphate) in floor dust and in airborne particles, with decreased cognitive performance as measured by the reasoning component of an intelligence test. This compound is a common flame retardant and is also used as a plasticizer.
Table 1 below lists three studies that employed data on school VOC concentrations together with estimates of the potency of VOCs to cause cancer. These studies produced predictions of the risks of increased cancer due to VOC exposures at school. For schools in the U.S., Chan et al. [17] estimated a total cancer risk of about 10 per million for a set of 15 VOCs, with formaldehyde the dominant source of risk. Using VOC data from eight naturally ventilated schools in Italy, another study [2], estimated cancer risks that were less than 10 per million in 21 of 23 classrooms, with risks between 40 and 50 per million in two classrooms. Benzene was the biggest source of risk. This analysis did not consider formaldehyde. The third study [5] estimated that the cancer risks of polycyclic aromatic hydrocarbons in airborne particles were less than one in ten million. Cancer risks less than one per million or ten per million are often considered negligible; thus, the typical cancer risks of VOCs in schools can be characterized as small, although in specific cases risks may be of concern. Because VOC levels in homes are typically higher than VOC levels in schools, and because more time is spent at home, the cancer risks of VOCs at school will typically be substantially less than the cancer risk of VOCs exposures at home.
In summary, concentrations of VOCs in schools are typically moderate and less than VOC concentrations in homes. Among VOCs, formaldehyde and terpene concentrations are often highest. Building materials and furnishings are usually a key source of formaldehyde and cleaning products are often a dominant source of terpenes. The available data suggest a possible association of increased respiratory health effects with increased formaldehyde concentrations; however, the data are insufficient for firm conclusions. The estimated cancer risks of VOC exposures in classrooms are on the order of 10 per million, but can be higher in specific classrooms. Among VOCs, formaldehyde appears to be the largest source of cancer risk. Cancer risks below one or ten per million are often considered negligible. Reducing indoor VOC sources and increasing ventilation with outdoor air are the primary options for controlling VOC levels in classrooms. More information on control measures for VOCs is available in the section of this website on VOCs.
Table 1. Results of studies of VOCs in schools.
|
Reference |
Location(s) |
Study site |
VOC Types |
Key findings |
|
[9] |
Minnesota |
Five classrooms in each of two elementary schools |
VOCs |
This study measured concentrations of 15 VOCs in the schools, homes, and outdoor air of students from two schools in Minnesota. Personal air (breathing zone) concentrations were also measured. Concentrations in schools were typically similar to concentrations outdoors and less than both personal concentrations and concentrations in homes. |
|
[10] |
France |
401 classrooms from 108 primary schools from 6 cities |
Aldehydes |
Median concentrations of formaldehyde, acetaldehyde, and acrolein were approximately 27, 9, and 2 µg m-3, respectively. Higher indoor concentrations of formaldehyde were statistically significantly associated with increased rhinoconjunctivitis but higher formaldehyde was not associated with past year asthma or past year allergic asthma. Also, there were statistically significant increases in past year asthma and past year allergic asthma, but not rhinoconjunctivitis, in classrooms with higher indoor concentrations of acrolein. There was no indication of an association of concentrations of acetaldehyde in classrooms with asthma or rhinoconjunctivitis. The analyses controlled for personal factors, but did not appear to control for concentrations of other measured pollutants. |
|
[18] |
California |
Forty daycare facilities |
SVOCs |
Flame retardant levels in early child education (daycare) centers in California sometimes exceeded no significant risk levels for carcinogens or reference levels for non-carcinogen effects. |
|
[17] |
United States |
NA |
VOCs Aldehydes |
This paper used data on indoor VOC and particle concentrations and equations indicating the potency of VOCs and particles to cause health effects to estimate health risks. Risks of VOCs and particles in schools were smaller that risks in homes. Particles posed higher risks than VOCs and, among VOCs, formaldehyde posed the largest health risk. |
|
[1] |
NA |
NA |
VOCs TVOC |
In this broad literature review, via analysis of data, the author showed that indoor TVOC concentrations increase with increasing indoor CO2 concentrations, which indicate decreased outdoor air ventilation rates. The author also concluded that TVOC concentrations were strongly related to dissatisfaction with IAQ, although only one study was cited supporting this conclusion. |
|
[2] |
Italy |
Eight naturally ventilated schools |
VOCs |
This studied measured VOCs in eight naturally ventilated schools in Italy, and also measured VOCs outdoors. Some classrooms had very low VOC levels, other classrooms had significant levels. Concentrations of terpenes were high in all classrooms. Benzene posed the highest cancer risk, indoor concentrations of benzene were similar to or higher than outdoor concentrations. 1,4 dichlorobenzene was elevated in 1 classroom. |
|
[19] |
California |
40 early child education facilities |
SVOCs |
This study measured concentrations of several phthalates in air and dust. The study was motivated by possible risks of reproductive toxicity and cancer. 82% to 89% of facilities had dibutyl phthalate (DBT) levels above reproductive health benchmarks and 8% to 11% of children less than age 2 had di (2-ethylhexyl) (DEHP) phthalate concentrations above cancer benchmarks. |
|
[3] |
Michigan |
64 elementary and middle school classrooms from nine schools |
VOCs |
The most prevalent VOCs were benzene, ethylbenzene, á-pinene, and limonene. Indoor VOC concentrations generally exceeded outdoor concentrations, but for most VOCs concentrations were characterized as low. Concentrations varied widely within and among schools. VOC sources included art rooms, science rooms, and indoor swimming pools. |
|
[16] |
Austria |
Nine elementary schools and 436 children |
SVOCs |
This study measured concentrations of phthalates and phosphororganic compounds (used as flame retardants, plasticizers, and floor sealers) in samples of floor dust and in samples of particles collected from air. Concentrations of airborne VOCs were also measured and student’s cognitive performance was measured using the reasoning component of an intelligence test. A decrease in cognitive performance of students was associated with higher concentrations of tris (2-chlorethylphosphase) in floor dust and in airborne particles, and the associations were statistically significant. Tris is a common flame retardant and is also used as a plasticizer. |
|
[13] |
Sweden |
23 classrooms in 8 primary schools |
VOCs Aldehydes |
This cross sectional study found higher concentrations of texanol, a common component of paints, associated with increased nocturnal breathlessness. Higher concentrations of TXIB, a common plasticizer in PVC floor coverings, were associated with increases in nocturnal and daytime breathlessness, doctor diagnosed asthma, and current asthma. The associations were statistically significant. Formaldehyde concentrations were not associated with respiratory symptoms. The analysis controlled for age and gender. |
|
[11] |
China |
30 classrooms from 10 naturally ventilated junior high schools |
Aldehydes |
Indoor formaldehyde concentrations averaged 9.4 µg m-3 with a standard deviation of 6.9 µg m-3. There were non-statistically-significant increases in airway symptoms and asthma outcomes in classrooms with higher formaldehyde concentrations. The analyses controlled for personal factors, the observed dampness in one school, and temperature, humidity, and concentrations of carbon dioxide, nitrogen dioxide, and ozone. |
|
[4] |
Australia |
One naturally-ventilated classroom in each of 25 primary schools |
VOCs Aldehydes TVOC |
This survey found that indoor outdoor ratios for VOCs were generally greater than unity in 19 of 25 schools, 41% of indoor VOCs were attributable to cleaning products, 23% were attributable to air fresheners, and 21% were attributable to arts and crafts materials. Emissions from building materials were a minor source. |
|
[14] |
Portugal |
76 classrooms in 11 elementary and secondary schools |
TVOC |
This survey in Portugal inspected 76 classrooms in 11 elementary and secondary schools, measured selected pollutants and used questionnaires to study health of 177 teachers. On average, indoor TVOC concentrations were a factor of 2.4 higher than outdoor concentrations. There were statistically significant increases in central nervous system symptoms, upper respiratory, symptoms and mucosal symptoms with increased TVOC concentrations. It appears that there was no control for potential confounders; thus, higher TVOC levels could have served as a proxy for some other exposure or factor causally related to increased symptoms. |
|
[20] |
Portugal |
73 classrooms in 20 primary schools |
VOCs Aldehydes |
Indoor concentrations of most VOCs were low, below 5 ìg m-3 and below guidelines. Formaldehyde had a mean concentration of 19.8 ìg m-3 with a standard deviation of 10.9 ìg m-3. Limonene concentrations were highest with a mean of 38.1, standard deviation of 44.5, and median of 23.1 ìg m-3 Indoor-outdoor ratios were greater than 6 for limonene, formaldehyde, and acetaldehyde. The two classrooms with graphic art activities had the highest concentrations of toluene and naphthalene. |
|
[21] |
Portugal |
52 naturally ventilated nursery and kindergarten classrooms in 9 facilities |
Aldehydes TVOC |
Formaldehyde concentrations were below the 17 ìg m-3 detection limit. Nursery school TVOC concentrations averaged 152 and 106 ìg m-3 in spring and winter. Kindergarten TVOC concentrations averaged 104 and 93 ìg m-3 in spring and winter. |
|
[15] |
Sweden |
129 staff in six primary schools |
VOCs Aldehydes TVOC |
Formaldehyde concentrations were below the 10 ìg m-3 detection limit. TVOC concentrations ranged from 70 to 180 ìg m-3. The risk of having at least one chronic sick building syndrome symptom was statistically significantly increased with higher TVOC concentrations. The risks of airway, general, and eye symptoms (but not dermal symptoms) were statistically significantly increased with higher TVOC concentrations. VOC concentrations were not significantly associated with the risks of new SBS symptoms. The extent to which the analyses models controlled for potential confounding factors is unclear. |
|
[6] |
Portugal |
Two naturally-ventilated classrooms in each of 14 elementary schools |
VOCs Aldehydes TVOC |
The sum of indoor concentrations of measured VOCs ranged widely from 37 to 317 ìg m-3. Formaldehyde concentrations ranged from 1 to 42 ìg m-3. In general, indoor VOC concentrations far exceeded outdoor concentrations. |
|
[5] |
Portugal |
Two schools |
VOCs TVOC |
This study compared measured IAQ parameters from a city center school and a suburban school. VOC levels were generally higher indoors than outdoors with particularly high levels of dichloromethane in both schools. Dichloromethane is common in aerosol air fresheners, deodorants, furniture polish, and cleaning compounds. The estimated cancer risk of polycyclic aromatic hydrocarbons was described as negligible. |
|
[8] |
California |
20 classrooms, grade kindergarten through 12 |
VOCs Aldehydes |
This paper reports on VOC measurements from 13 portable and seven traditional classrooms. During occupancy, formaldehyde averaged 20 ìg m-3 overall, and 31 ìg m-3 in portable classrooms. For most other VOCs, mean concentrations were less than 1 to 5 ìg m-3. Average VOC concentrations were higher for á-Pinene and ä-Limonene. Cleaning products are a common source for these two compounds. |
|
[12] |
Sweden |
28 classrooms from 11 secondary schools |
VOCs Aldehydes |
Formaldehyde and 14 other VOCs were measured in each classroom and asthma symptoms and demographic characteristics of 627 students was assessed with a questionnaire. After control for personal factors, current asthma was statistically significantly associated with higher formaldehyde and higher total VOC concentrations at school. |
|
[22] |
Turkey |
Two classrooms in each of three elementary schools |
VOCs Aldehydes |
This small study measured VOCs in one classroom, one kindergarten room, and outdoors at each school and used the concentration data to estimate relative potential health risks. Formaldehyde posed the highest health risks, followed by naphthalene, benzene, and toluene. |
|
[23] |
Greece |
15 schools, one classroom per school, grade levels were not reported |
Aldehydes TVOC |
This studied measured a variety of IAQ parameters, including formaldehyde and TVOC concentrations. Formaldehyde concentrations ranged from 23 to 77 ìg m-3, which is below the recommended maximum of 100 ìg m-3 by the World Health Organization, but well above limits recommended by some other organizations. TVOC concentrations ranged from 1300 to 6400 ìg m-3, which is higher than reported in most other studies. |
|
[7] |
Korea |
One classroom, one laboratory, and one computer classroom in each of 55 schools |
Aldehydes TVOC |
The average measured TVOC concentration was 374 ìg m-3 in classrooms, 176 ìg m-3 in laboratories, and 186 ìg m-3 in computer rooms. The average measured formaldehyde concentration was 100 ppb in classrooms, 180 ppb in laboratories, and 90 ppb in computer rooms. Formaldehyde concentrations were higher in newer classrooms and averaged 160 ppb in classrooms with an age less than one year. |
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