A breath of fresh air, indoors
Indoor air is an under-recognised avenue for exposure to potentially harmful pollutants. Fortunately, there are many actions you can take to minimise the health risks. This is why it is important to be getting fresh air, indoors.
With Australia and New Zealand having lost much industrial activity to countries overseas and as the proportion of internal combustion vehicles on the roads continues to fall as they are substituted with electric cars, it is easy to mistakenly conclude that the challenge of pollution has largely been solved. Against this background, the issue of indoor air quality often receives less attention than it deserves. In both countries, the average person spends about 90 per cent of their time indoors, underscoring the importance of this issue.
In addition to chemicals, other indoor pollutants include dust, mould, mites, pollen, microplastics and bacteria. Studies have found that levels of indoor pollution can be two to five times higher than outdoors. As the average home today is more airtight than a decade or two ago, reduced airflow can lead to an increased concentration of these pollutants.
Globally, around 30 per cent of people use fuelwood for cooking, heating or lighting, creating harmful particulates. Short-term symptoms include eye, nose and throat irritation. Long-term effects can include reduced lung function and the development of heart and respiratory disease. The World Health Organization (WHO) backs the use of LPG instead, which has been found to roughly halve indoor particulate levels. Neither fuel is ideal from a climate change perspective. In arid areas especially, deforestation caused by sourcing wood for domestic consumption is a serious problem. Another direction involves the spread of ultra-efficient cookstoves that reduce pressure on wood sources. Additionally, design features that minimise particulate emissions.
The role of chemical sensitivity
People with multiple chemical sensitivity (MCS) are most likely to be affected by indoor pollutants. These are individuals who may encounter symptoms such as nausea, fatigue and dizziness. Traditionally, there was a tendency to think that this condition was psychological in origin. However, such a notion is challenged by a 2023 study that revealed brain imaging differences including the sensitisation of certain receptors.
Those with MCS need to be vigilant about minimising a wide range of chemical exposures. Volatile organic compounds (VOCs), a class of chemicals that includes formaldehyde and benzene, are the number-one trigger for people with MCS. A survey carried out in 2019 looked at people in the UK, USA, Australia and Sweden and found that about a third considered themselves sensitive to synthetic fragrance, a product usually made with VOCs.
The chemical sensitivity issue goes beyond domestic settings and extends to a range of other environments including offices, shopping centres, hospitals and classrooms.
Sick building syndrome
Decades ago, a pattern of symptoms was identified in office workplaces, including throat irritation, headaches and difficulty concentrating. This came to be known as “sick building syndrome”, a term coined by the WHO in 1986. Likely causes are thought to include poor ventilation, chemicals, low humidity, unhealthy positive ions emitted by electronics and inadequate lighting.
Sick building syndrome has a negative effect on productivity, in addition to contributing to a poorer-quality experience at work. The easiest way to confirm its existence is when symptoms reliably occur while in the building and go away when away from it.
Strategies include reducing the time spent in the office, removing the sources of chemicals where feasible, and improved ventilation. Maintaining a humidity level between 40–70 per cent, negative ion generators and natural or improved lighting can also be effective.
Gas as a common pollution source
Inside homes, gas stoves and unflued gas heaters emit nitrogen oxides, carbon monoxide, formaldehyde and benzene. Of these, the last two are known to cause cancer. Nitrogen dioxide is known to be a source of asthma. Research from the US indicates that about one in eight cases of childhood asthma is specifically caused by the use of gas stoves. On these stoves, a yellowish flame indicates unhealthy carbon monoxide and soot emissions. On the other hand, a blue flame is burning at its optimal efficiency.
Avoiding gas or, alternatively, switching from gas to electricity are beneficial both from a health and environment standpoint. Natural gas (methane) and LPG (often a propane and butane mixture) are both fossil fuels by definition, unlike electricity, an increasing proportion of which is now coming from renewables. When using a gas stove, and for venting particulates released from the food being cooked, ventilation and the use of an extractor fan are both helpful. When looking at a gas heater purchase, far healthier is the flued type. With a vent that passes through the wall behind the heater, nearly all the nasties are evacuated outdoors. However, one significant downside of vented heaters is that they are not portable.
In Australia and New Zealand, there are climate-related moves towards phasing out mains gas connections to new dwellings. The state of Victoria banned these connections at the start of 2024. In New Zealand, the Climate Change Commission put out draft advice recommending an end to domestic grid and bottled LPG connections by 2025.
Other indoor exposures
Synthetic scents and air fresheners are commonly used in living spaces and bathrooms. A better alternative is to use natural products or open a window instead.
Harsh cleaning chemicals such as ammonia, bleach and other VOC emitters have been found to cause damage to the lungs. Concerningly, the damage is roughly on par with the effects of smoking. The effects are primarily felt by professional cleaners, but also apply to householders. Choose natural alternatives if possible.
Candles made from paraffin wax can emit low levels of benzene and toluene. Unscented candles are better, and beeswax is the best type of candle for protecting one’s health and the environment.
Tobacco smoke, vape emissions and most candles are sources of harmful particulates in the sizes known as PM10 and PM2.5. Of these two, PM10 enters the lungs, while the smaller PM2.5 particles go deeper into the lungs and are more dangerous. Some indoor particulate matter originates from outside the home, from bushfires, diesel vehicles, industry and wood heaters.
Toxic lead can occur in pre-1970 paint. Particles can become airborne during renovations on older houses unless safety precautions are followed. It is more harmful to children than to adults and can impact their IQ.
According to a 2008 study, new PVC shower curtains can off-gas 108 different chemicals, mostly phthalate plastic softeners and VOCs. The best option when making a purchase is a PVC-free shower curtain.
Tackling mould
One non-chemical indoor air issue is mould, which may be evident on objects, walls or ceilings. A musty smell also indicates its presence. In a survey, 34 per cent of Australian homes self-reported mould. Meanwhile 37 per cent of New Zealand homes were found to have visible mould. This problem is worse in humid environments and in rooms that receive little direct sun exposure. Health effects can include asthma attacks and allergic reactions and are worse for people with weak immune systems.
Firstly, stop the entry of water, via the roof or other routes. Preventative measures can include ventilation, the use of extractor fans in kitchens and bathrooms. Utilise dehumidifiers and anti-condensation paint in rooms susceptible to black mould. Surface mould can be removed with a mixture of vinegar and essential oils such as clove, lemon and tea tree. Bleach is not recommended because it can bleach the mould instead of killing it. In worst cases, some areas of the wall may need to be removed and replaced. If living in a rented property with serious mould problems, it may be best to move if possible.
New car smell
The distinctive smell associated with new cars tends to appeal to certain people and can even have prestigious associations. However, this overlooks the dangers from the chemicals responsible, which are used in the making of leather, plastics and synthetic materials. A 2023 Chinese study identified the VOC acetaldehyde at 60 times the baseline safety level and formaldehyde at 35 per cent above the suggested limit.
This same study determined that after 10 minutes, these chemicals were capable of causing lethargy and drowsiness, posing an added safety risk on the roads. Other short-term symptoms may include dizziness, nausea and shortness of breath, while most studies on the new car smell phenomenon point to an elevated risk of cancer and birth defects. Exposure is accelerated when a new car is parked in the sun. The chemicals outgas more quickly in the sealed environment.
When making a decision on a car purchase, it’s worth considering that a new vehicle will have lost most of its smell within a year, and a car that is several years old is likely to be free of new car odour. If you have a new car, remedies include ventilation, removing any protective plastic coverings and leaving trays of absorbent sodium bicarbonate under the seats.
Curbing indoor pollution
Encouragingly, some industries have been fairly proactive in reducing chemical emissions from their products, but this is no complete solution. At a time when neither Australia nor New Zealand has government standards for indoor air quality, there are a few constructive things that people can do.
How air quality can be managed
Manual ventilation is a key factor, as is regular cleaning and vacuuming. Treading on carpets alone causes a plume of particles to be launched into the air. The best type of vacuum is one with a HEPA (high-efficiency particulate air) filter that captures virtually all particles, including the smallest ones, and produces far less dust.
Air purifiers are electrical appliances, usually cylinder-shaped, that generally consist of a fan combined with one or more filters, one of which is usually a HEPA filter. These purifiers often have a UV light feature that kills a lot of nasties.
Ozone generators are sworn by some to work against pollutants such as mould and smoke. It is very important not to run such a generator while anyone is in the same room because of the way that this reactive chemical attacks the body. Ground-level ozone has a relatively short lifespan and will dissipate of its own accord. If using such a generator, it is recommended to limit the treatment time, leaving some hours between the end of the cycle and spending time in the room, as well as venting any remaining ozone in the air. The use of these generators is generally discouraged by government agencies, based on the risks associated with their misuse and because it is argued that their air-quality claims have limited supporting scientific evidence.
Natural solutions
Plants can also purify air through phytoremediation. A 1989 NASA study found spider plants, snake plants and peace lilies effective at removing VOCs in sealed chambers. However, the American Lung Association points out that a large number would be required to make a real difference and that any effect would be dwarfed by the far more pivotal issue of the air exchange rate.
What else can people do?
Far more high tech are digital air-quality monitors, which give real-time readouts of CO₂, VOCs and particulates, often with colour-coded warnings. Elevated CO₂ can cause brain fog and other health issues and signals a need for better ventilation. Widespread use of these tools could improve health outcomes on a larger scale.
Indoor air pollution is a significant challenge. But there are a range of steps that people can take to tackle it.
