6.  POLLUTION INDOORS

i.    General:

With the many issues and considerations facing environmental toxicologists one of the more over-looked areas concerns the various forms of pollution and toxicants indoors. Indoor pollution takes on many forms: chemicals used in the manufacture of many products such as carpets, furniture or paints, or through the gradual accumulation of agents. In Canada, with a long, cold, winter climate extensive periods of time are spent indoors where highly energy-efficient buildings can trap and recirculate pollutants. Dusts, pollens, fugitive gas emissions, radon build-up, materials trapped in carpets all add to an unhealthy indoor atmosphere. In developing nations, however, there are different concerns: use of indoor fire for cooking or heating can directly produce toxic vapours and subsequent ill health. 

ii.    Specific Indoor Toxicants:

In many nations people spend more time within their residences than outside, continually being exposed to a specific indoor environment. With modern, highly energy efficient homes there is a constant recirculation of the indoor atmosphere and little uptake of fresh air.  Any chemicals / toxicants present in this type of environment will persist for extended periods of time. One of the most significant toxicants for indoor pollution is formaldehyde, typically found at higher levels indoors than outside. Formaldehyde is suspected as being involved in respiratory, allergy and other health ailments as well as being a suspected carcinogen. Formaldehyde can enter the indoor environment in a variety of ways: as a component of the adhesives in plywood / particle board, or as a plastic resin component used in numerous synthetic materials (carpets, fabrics, foams, etc.). During the first few years following manufacture small amounts of formaldehyde are released as gas from the many potential sources. Another contribution comes from the smoke of cigarettes which  can release small amounts of formaldehyde along with another toxicant, carbon monoxide. 

Carbon monoxide is often released as a by-product of combustion, in small amounts from cigarettes but in much larger amounts during the combustion of fossil fuels. Faulty furnaces, water heaters and/or gas dryers can all release carbon monoxide. In high concentrations carbon monoxide (an odourless, colourless gas) is fatal. In lower doses symptoms of carbon monoxide poisoning include headache, fatigue, drowsiness and other symptoms.  Installation of a simple carbon monoxide detector can monitor gas levels and offers relatively inexpensive security to homeowners.       

Radon Gas is a radioactive gas which can migrate through soils and accumulate in the basements of residences. Produced by radioactive break-down in the soil, it seeps through cracks and fissures in foundations and enters basements. The situation is made more problematic if there is little ventilation or air-exchange in the vicinity allowing the radon to concentrate, although older residences with cracked, unstable foundations are far less likely to be as air-tight as their modern counterparts. Radon accumulation can also be a problem in larger underground areas such as natural caverns or mines. The highest residential concentrations of radon in Canada are found in Winnipeg, Manitoba. Studies are ongoing to examine the role of radon exposure to increased incidence of lung cancer,  but "safe" exposure levels have yet to be established.  

Dust, pollen, and other air-borne particulates are also a concern as indoor air pollution. In Canada, with long winters and indoor air being continually recirculated and heated there can be considerable indoor pollution from air-borne particulates.  Symptoms can take on a range of forms; from fairly subtle sneezing, allergy-like irritations to more serious health problems such as asthma attacks and other respiratory problems. Continual recirculation of indoor air may deliver heat / cooling, but it is also an excellent medium for the air-borne pollutants. Fortunately, reduction of airborne particulates can be achieved rather easily. Modern furnaces with powerful fans that circulate air are equipped with filtration devices. These filters may be a simple loosely weaved polymer, or a complex permanent electrostatic filter.  In terms of effectively reducing air-borne particulates the choice of filtration type is important. Inexpensive, low-quality filters remove only relatively large particles and retain only a small  per cent of air-borne particulates. The best reduction in both macroscopic and microscopic air-borne particulates is achieved through electrostatic filtration which uses small surface charges to trap particles to small to be removed by physical filtration. These filter systems are available as disposable "standard" furnace filters or as permanent electrostatic filtration systems.

iii. Indoor Pollution - A Residential Case Study: Frederick Street, Halifax:

Residents of Frederick Street in Halifax have first-hand experience with accidental exposure to toxic chemicals. The exposure is direct: unidentified industrial waste has been seeping into the basements of local homes. The area has an unfortunate combination of factors which allow the ground water to accumulate industrial hazardous waste from several potential sources. In the immediate vicinity there are abandoned coke ovens from the Sydney steel mill, local rail-beds, an over-capacity municipal land-fill and tar ponds with hazardous sludge, all in relatively close proximity.  Recently (May 1999) residents were evacuated from their homes after a suspected toxic yellow/orange "slime" began seeping into residential basements in the area. The material is suspected of having dangerous levels of arsenic and other potentially hazardous compounds. For some time residents have been experiencing ill health (nausea, vomiting) and have been working to focus attention on the situation. This is the third time residents have had testing conducted on residues in their residences: last summer the federal government actively treated the area to reduce arsenic levels. The fact that more toxic waste continues to be rapidly leached through groundwater fuels suspicions that there are considerable concentrations of toxic materials in the immediate area and that the problem requires extensive clean-up and remediation.

As in the many cases of environmental contamination there is considerable debate over who is specifically responsible for the situation: the steel mill, the railway, or the municipal  land-fill. While determining specific responsibility in the matter may take many years, there is still the immediate need of the residents to be addressed.

 Frederick street is only a single example of industrial pollutants directly affecting private residents. There are many cases of this nature (re: Love Canal), and likely there will be more discovered in the  future. 

  Written Assignment #2 – Upon completion of this section contact the instructor for your second assignment.