In contrast to blue collar industrial workers, white collar workers (including office workers and teachers) are often thought to work in nonhazardous environments. In fact, a long history exists of concerns for office and school worker health in relation to large buildings that require mechanical ventilation and air conditioning. In the early decades of the twentieth century, ventilation standards were developed to provide for control of body odor in indoor environments where large numbers of people congregated. As early as the 1920s, ventilation parameters were established to control transmission of infectious diseases. Public interest in indoor environmental quality arose in the late 1970s after changes in building environments and their ventilation occurred in the wake of the energy crisis in the USA. Office workers in diverse parts of the USA had symptoms of headache, mucous membrane irritation and difficulty concentrating in tight temporal association with occupancy of their work buildings. The public health response to investigation was stymied when industrial hygienists failed to measure any contaminant at levels exceeding industrial health standards. Some public health professionals attributed widespread complaints in particular buildings to mass psychogenic illness, although the type of symptoms and endemic nature of complaints did not meet criteria for hysteria. European investigators took an epidemiologic approach and established building-related risk factors for the common symptoms of mucous membrane irritation and discomfort. These included air conditioning, extent of carpet and fleecy materials such as textile-covered partitions and chairs, open shelving with paper in the indoor environment, housekeeping and eventually outdoor air ventilation rate and ventilation maintenance practices, among others.

In the USA almost 70% of the workforce is employed in nonindustrial, indoor settings. Office and administrative support occupations accounted for an estimated 20 million workers in the US census in 2000, and management, business and financial operations occupations accounted for an additional 16.6 million. In 2006, the US census bureau estimated that there were 6.8 million school teachers. Schools also employ nonteaching staff with work environments similar to those of teachers.

In keeping with the historical view that office workers have few occupational risks, this group is commonly used as the comparison group in analyses looking for occupational risk of respiratory conditions. Population-based information on health risks to office workers is meager. A study of middle-aged professional women in France documented that, in comparison to work in naturally ventilated buildings, work in buildings with heating, ventilation and air-conditioning (HVAC) systems was associated with an increased risk for annual visits to otorhinolaryngologists, as well as sickness absences. These observations hint that occupational respiratory disease occurs in the indoor environment and may present in pulmonary and occupational medicine practices.

Using office workers as a comparison group, an analysis of 20,991 US adults, 18 years of age and older who participated in the 2001 National Health Interview survey, found that workers in elementary and secondary schools and colleges had an increased risk for asthma. It is of interest that from 1990 to 1999, US secondary school teachers had excess proportionate mortality from asthma as compared with the expected based on all occupations. In state-based reporting of physician-diagnosed work-related asthma (WRA) from 1993 to 1995, 1101 cases were identified in California, Massachusetts, Michigan and New Jersey. Indoor air pollutants (including those arising from poor ventilation, pesticides, dusts and dirt, molds, environmental tobacco smoke, paint odors and other nonspecific building odors) were reported as a cause of both new-onset and work-aggravated asthma in all four states and represented the most frequent putative cause. Nonindustrial workers reportedly affected by indoor air pollutants included teachers, office workers, nurses, secretaries, librarians, computer operators and programmers, technicians and clerks. A subsequent analysis of 2995 WRA cases reported between 1993 and 2000 from the same four states found that 265 (9%) WRA cases were employed in educational services, of which 69% (182/265) were new-onset asthma. Indoor air pollutants, mold, dusts and cleaning products were the most frequently reported agents. There is some evidence that respiratory conditions other than asthma are found in excess in teachers. Teachers had excess work-related eye, nose and throat symptoms, wheezing and five or more episodes of cold or flu in the past year over other working women. Some of these health effects may have been related to exposure to children with infectious conditions. A large case-control study of sarcoidosis in the USA started in the mid 1990s (the ACCESS study) found that elementary and secondary school teachers were at an elevated risk for sarcoidosis.

The little information available on the proportion of office or school buildings in the USA that have dampness problems, or the severity of such conditions, indicates that the problem is widespread. From a large study of US office buildings not known to have indoor air quality complaints in the 1990s, it was found that 85% of 100 buildings had incurred some past water damage, while 43% of the buildings had current water damage. In 1995, the Government Accounting Office reported that about 30% of schools in the USA needed repairs to plumbing, roofs or external walls, windows and doors. Individual buildings can become damp indoor environments through being poorly designed, poorly built, poorly maintained or poorly run.

Since the late 1990s, three influential literature reviews (two from Europe and one from the USA) have concluded that living, working or going to school in damp indoor environments poses a respiratory health threat. Despite the absence of a standardized way to describe levels of dampness in buildings, studies have shown an increasing risk for respiratory symptoms in occupants with increases in the number of signs of dampness, water incursions and water damaged materials, both as reported by occupants or as scored by researchers. A NIOSH study of college employees demonstrated that exposure to dampness, as estimated by weighting the dampness score of individual rooms by employees’ time spent in the specific rooms, was a good predictor of employees’ respiratory illnesses. The dampness scores were calculated based on the extent of water stains, visible mold, mold odor and moisture observed by industrial hygienists in seven room components (walls, ceiling, floor, windows, ventilation system, furniture and pipes). A Finnish research group has also developed a moisture damage index based on a study of homes. The index was based on the location of damage, type of damage, duration, type of damaged material and size of damaged area, as measured by civil engineers. They also demonstrated that this index was correlated with health symptoms.

Dampness itself cannot be a cause of respiratory disease, and there is still uncertainty about the causal agents of respiratory problems related to dampness. However, there is growing epidemiological evidence of associations between respiratory health effects and microbial contaminants derived from mold and bacteria, allergens from dust mites and cockroaches, and chemical agents released from wetted building materials and furnishings.

Molds

Volatile organic compounds are defined as organic compounds with boiling points in the range of 50-250°C. In indoor environments of schools and offices, there are many sources of VOCs, such as building materials (especially in new buildings), furniture, plastics, floor wax, cleaning agents, occupants and photocopiers. There are several thousand VOCs, and over 900 VOCs have been identified in indoor environments. Acetone, aliphatic hydrocarbons (hexane, octane, decane, etc.), aromatic hydrocarbons (toluene, xylene, benzene, etc.), chlorinated solvents (methylene chloride, trichloroethane, etc.), n-butyl acetate, dichlorobenzene, 4-phenylcyclohexene and terpenes are among the most commonly found VOCs. Since measurement and identification of an individual VOC with very low concentration is expensive, total VOCs are frequently measured. There is no standard for total VOCs in the USA and Canada, nor are consensus guidelines available from the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE).

Microbial volatile organic compounds can be produced while microorganisms, especially mold, actively grow in damp building materials. In laboratory studies, more than 200 VOCs have been recognized as having microbial origins. Recently, the American Industrial Hygiene Association’s Field Guideline for the Determination of Biological Contaminants in Environmental Samples identified 14 compounds as potential MVOCs (3-methyl furan, 1-butanol, 3-methyl-1-butanol, 3-methyl-2-butanol, 2-pentanol, 2-hexanone, 2-heptanone, 3-octanone, 3-octanol, 1-octen-3-ol, 2-octen-1-ol, 2-nonanone, borneol and geosmin), which were consistently detected by more than three authors in field surveys. Unique musty, earthy, mushroom-like or mold odors in damp/mold buildings are due to several MVOCs (e.g. geosmin, 2-methyl-iso-borneol or 8-carbon MVOCs). Many researchers in epidemiological studies have successfully used mold odor as a useful predictor for adverse health effects in damp indoor environments. However, no MVOC measurements have been shown to be predictive of health risk.

Formaldehyde, a well-known irritant and sensitizer, is a colorless gas and can be recognized by pungent odor at a concentration higher than 0.2 parts per million (ppm). Building materials and furnishings (e.g. particle board, carpets and fabrics), cleaning agents and adhesives can release formaldehyde. Irritant effects have been found to occur when formaldehyde is present at levels above 0.1 ppm. Studies in schools have reported levels generally at 0.05 ppm or less, but some concentrations above the irritancy threshold were found. A study of Italian office workers with symptoms of irritation while working in newly renovated offices, found levels of formaldehyde from 0.07 to 0.4 ppm. The ACGIH classified formaldehyde as a ‘suspected human carcinogen’ with a ceiling threshold limit value of 0.3 ppm. NIOSH also identified formaldehyde as a potential occupational carcinogen and recommended a time-weighted average (up to a 10 hour workday and a 40 hour working week) exposure limit of 0.016 ppm and a 15 minute-average ceiling limit of 0.1 ppm.

Phthalates are plasticizers added to polyvinyl chloride (PVC) products to keep them pliable, as well as to a number of other products such as paints, glues, cleaners and cosmetics. They are ubiquitous in the environment. There are public concerns about the health effects of phthalates, since they may act as endocrine disruptors and can affect the reproductive system. Recent research on children in homes and schools has indicated that phthalates and other plasticizers and their breakdown products are associated with respiratory symptoms, asthma, rhinitis and eczema. Moisture can lead to increased release and breakdown of plasticizers from PVC-containing building materials such as floor tiles and carpet backing; thus increased exposure to phthalates in damp, water-damaged schools and offices may be a concern. More research is needed to understand exposure-response relationships between phthalates and respiratory health effects.

A 2000 Institute of Medicine (IOM) report on asthma and indoor air exposures found sufficient evidence of a causal relationship between the development of asthma and house dust mite, limited or suggestive evidence of an association between the development of asthma and exposure to cockroach in preschool-aged children, and insufficient evidence to make a conclusion on the development of asthma and exposure to cockroach (in people other than preschool-aged children), cat, dog or rodents. In regards to exacerbation of asthma, the IOM committee found sufficient evidence of a causal relationship with exposure to cat, cockroach and house dust mite, sufficient evidence of an association with exposure to dog, and insufficient evidence to make a conclusion regarding exposure to rodents.

Dust mites thrive in warm moist places, and keeping relative humidity below 50% is a recommendation for reducing dust mites and their allergen levels. The dust-mites commonly found in indoor environments such as homes, schools and office buildings are Dermatophagoides farinae (Der f) and Dermatophagoides pteronyssinus (Der p). Their Group 1 allergens, Der f 1 and Der p 1, are often assessed for associations with allergy and asthma. There is a dose-response relationship between sensitization and exposure to dust mite allergen. Research on children has indicated that exposure to 2 μg/g or more of Der p 1 allergens in dust increases the risk of sensitization (as measured by positive skin tests or presence of IgE antibodies), and the development of asthma, although there is some evidence that sensitization can occur at lower levels. Exposure to 10 μg/g Der p 1 or more in dust increases the risk of asthma symptoms in mite-allergic people, but the relationship is not clear. Concentrations of Der f 1 and Der p 1 found in office building and school building dusts are usually lower than the levels found in dust from homes. Furthermore, the opportunity for exposure to dust-mite allergens may be lower in nonresidential buildings since allergens are contained in particles of mite feces which do not remain suspended in the air for long if disturbed. In homes, bedding is a major source of mite allergen exposure.

Cat allergens are ubiquitous, being found in homes with and without cats and in many types of public buildings, including schools and office buildings. They are sticky and are carried into buildings on clothing. There is a proposed threshold of 8 μg/g of the major cat allergen Fel d 1 for sensitization, while a level of 1 μg/g has been reported to elicit asthma symptoms in sensitized people. The allergens are carried on a range of particle sizes, but are often on small particles that can remain airborne for long periods of time after dust has been disturbed.

There are many species of cockroaches, but the German cockroach Blattella germanica (Bla g) is commonly found in homes and schools, and to a more limited extend in office buildings. Its major allergens Bla g 2 and Bla g 1 have been widely used to assess exposure to cockroaches in relation to asthma. The proposed threshold levels of cockroach exposure is 2 units per gram (U/g) allergen in dust for an increased risk of sensitization and 8 U/g of allergen in dust for asthma symptoms. Cockroach allergens are usually carried on larger particles and thus do not remain suspended in the air for long after disturbance of dust.