Formación del profesorado a través de las redes sociales 69

Health effects from lAPs may be experienced soon after exposure or possibly years later. Firstly, immediate effects may show up after a single exposure or repeated exposures. These include irritation of the eyes, nose and throat, headaches, dizziness, and fatigue. Such immediate effects are usually short term and treatable. The likelihood of immediate reactions to TAP depends on several factors. Age and pre-existing medical conditions are two important influences. In other cases, whether a person reacts to a pollutant depends on individual sensitivity, which varies from person to person. Secondly, other health effects may show up only after long or repeated periods of exposure. These effects which include some respiratory diseases, heart disease, and cancer, can be fatal.

Immediate effects reported by building occupants have been classed in various categories whose most widely referred to are:

• Multiple Chemical Sensitivity • Building Related Illness • Sick Building Syndrome

These categories are now presented in the above order; the sick building syndrome (SBS) being emphasised.

1.4.1. Multiple Chem ical S en sitivity

Multiple Chemical Sensitivity (MCS) is postulated to be the development of responsiveness, including manifestation of often disabling symptoms, to extremely low concentrations of chemicals following sensitisation.^®

1.4.2. B uildings R e la ted R lness

The Building Related Illness (BRI) term is used when symptoms of diagnosable illness are identified and can be attributed directly to airborne contaminants. BRI complaints include cough, chest tightness, and fever, chill and muscles aches. The BRI symptoms can be defined and have clearly identified causes. Complainants may require prolonged recovery times after leaving the building.^®

1.4.3. Sick Building Syndrom e

The term Sick Building Syndrome (SBS) is used to describe situations in which building occupants experience acute health and comfort effects that appear to be linked to time spend in a building, but no cause or specific illness can be identified. The complaints may be localised in a particular room or zone, or may be widespread throughout the building. The complaints may decline short time after leaving the building."^^

Inadequate ventilation, biological contaminants such as bacteria, moulds, pollen and viruses, and chemical contaminants are thought to play important roles in SBS. However, the main cause is believed to be common VOCs found in indoor environment. These elements may act in combination, and may supplement other complaints such as inadequate temperature, humidity, or lightning. It is also generally recognised that

psychological factors can influence an individual’s perception of indoor air health effects as they can influence other disease processes/^

The SBS is characterised by a range of symptoms including, but not limited to, central nervous system complaints such as headache and fatigue, eye, nose, and throat irritation, and dry skin. Contrary to BRI, the SBS is by no means a well-defined medical entity, and often the symptoms vary widely from person to person within a given building.^

Among the various symptoms evoked, sensory responses, especially irritative response figure prominently. As Molhave noted, “SBS, in brief, is an unexplainable sensory irritation appearing in a large fraction of the occupants of the affected building”. Similarly, Cain pointed out that when air smells bad, or when it irritates the nose or eyes, people commonly feel threatened.^^ For these reasons, in the non-industrial environment, nasal irritation (or pungency) together with odour perception is believed to be appropriate indicators of indoor air quality.^^

In studies on these chemosensory issues, VOCs have deserved particular attention.^^ Actually rarely does a VOC lack the potential to cause irritation and experiments could be developed to set standard for VOCs.

1.4.4. Volatile Organic C om pounds a n d B uilding-R elated Com plaints

Several factors have led specialists to think that VOCs could adversely contribute to indoor air quality. First, both in terms of number of compounds and concentration, VOCs predominate in indoor air.^^ VOCs are found at higher concentrations in indoor air compared to outdoor concentration. Secondly, complaints about indoor air are typically more prevalent in new or refurbished buildings when concentrations of VOCs are highest. Furthermore, many VOCs can cause or contribute to a wide range of health effects from non-specific sensory responses to specific toxicity to target organs. In Table 1.6 are listed some selected VOCs and their various impacts on human beings whose irritative response figured prominently. However, although mixtures of VOCs have the potential to affect indoor air quality, studies of the relation between exposure to indoor air VOCs and symptoms reported by building occupants have shown only a sparse or inconsistent association between observed VOCs levels and health effects."^^

Probably, the most informative studies on health effects of VOCs based on the TVOC method are obtained from simulated chamber studies using defined concentrations of mixtures and defined endpoints. Human subjects were exposed to a typical mixture of twenty-two common VOCs (the “Molhave mixture”) at different concentrations.^"^'^^ They follow a gradient from sensory effects (for example odor at almost 3 mg.m'^) to indications of subacute stress reactions at about 25 mg.m'^. Sensory responses and behavioural impairment were examined through the use of questionnaires and objectives tests. The major findings of these studies are summarised:

• Complaints of poor air quality as a result of perceived odour intensity were highly correlated with total VOC concentrations and were significant at the lowest tested concentration, Bmg.m'^.

• Irritation of nose, throat, and eyes was significant at or above 5 mg.m'^.

• Other symptoms such as headache and general discomfort appeared at 25 mg.m'^. • There was some limited but still controversial evidence to suggest that behavioural

impairment such as reduced short-term memory may appear at 25 mg.m'^.

While the above are the concentrations associated with SBS symptoms in controlled experiments, Molhave^^ has found that SBS complaints are likely to arise when total VOC concentration exceed 1.7 mg.m'^. This suggests that building occupants may respond to VOCs in the real-life environment at a lower concentration than in a controlled environment. Furthermore, these real-life level are below those at which toxicological or sensory effects would be expected in humans, see Tables 1.7 and 1.8 for formaldehyde as an example. These findings show how it is difficult to set guidelines and standards for VOCs that are needed to reduce exposure to VOCs and, by extent, to improve indoor air quality and to reduce discomfort and illnesses.

Moreover, concerns about low-level exposures usually arise around the perception of odor and irritation, and VOCs are considered to be only one of a combination of factors that cause such complaints. Studies of low levels of VOCs and sensory responses that involve odor, nasal pungency, and eye irritation show that mixtures of VOCs cause responses at concentration far below what would be expected for each component of the mixture. It seems that increasing the number of VOCs in a complex mixture can lower the thresholds for odor as well as for eye and nasal irritation.

T a b le l.6 . Health Effects of selected Volatile Organic Compounds

VOC Health Effects

Benzene Carcinogen; respiratory tract irritant

Xylenes Narcotic; irritant; affects heart, liver, kidney, and nervous system Toluene Narcotic; possible cause of anemia

Styrene Narcotic; affects control of nervous system; probable human carcinogen

Toluene diisocyanate Sensitizer; probable human carcinogen Trichloroethane Affects central nervous system

Ethyl benzene Severe irritation of eyes and respiratory tract; affects central nervous system

Dichloromethane Narcotic; affects control of nervous system; probable human carcinogen

1,4-Dichlorobenzene Narcotic; eyes and respiratory tract irritant; affects heart, liver. kidney, and nervous system

Benzyl chloride Central nervous system irritant depressant, affects liver and kidney; eye and respiratory tract irritant

2-Butanone Irritant; central nervous system depressant Petroleum distillate Affects central nervous system, liver and kidneys

4-Phenycyclohexene Eye and respiratory tract irritant; central nervous system effects Sources adapted from ref. US EPA ‘introduction to lAQ’ report no. EPA/400/3-91/003,\j(/ashington, DC,

1991.

Table 1.7. Indoor sources for formaldehyde exposure

Sources Concentration

Cigarette smoke 40 ppm in 40 cm'^ per puff

Dose per pack for smoke 0.38 pg per pack

Environmental tobacco smoke 0.25 ppm

Clothing made with synthetic fibres

M en’s polyester-cotton blend 2.7 ng.g ' per day

Women’s dress 3.7 ng.g ' per day

Furnishings

Particle board 0.4-0.8 pg.g ‘

Plywood 1.5-5.3 pg.g '

Panelling 0.9-21 p g .g '

Draperies 0.8-3 pg.g '

Carpet / upholstery fabric = 0 . 1 ppm

Effects Formaldehyde Concentration (mg.m' )

Odour detection threshold 0.06-1.2

Eye irritation threshold 0.01-1.9

Throat irritation threshold 0.1-3.1

Biting sensation in nose and eye 2.5-3.7

Tolerable for 30 minutes (lacrymation) 5.0-6.2

Strong lachrymation, lasting for 1 hour 12-25

Danger to life, oedema, inflammation. 37-60

pneumonia

Death 60-125

Adapted from Ref. 32