午夜福利1000集合

AS I weave through the London traffic on my bike, I always worry about the filthy air I am breathing. It is a relief to get back inside, where the air is sweeter and, you might think, better for me. But that turns out to be a false sense of security.

鈥淧eople don鈥檛 imagine that there is pollution indoors; it is perceived as a protective place,鈥� says Corinne Mandin at France鈥檚 . 鈥淏ut there are more pollutants in buildings than in outdoor air.鈥�

Thanks in no small part to covid-19, which focused minds on air quality and ventilation of enclosed spaces, the long-neglected issue of indoor pollution is finally being taken seriously. Deadly seriously, in fact, as it dawns on scientists that the pollutants we encounter in our homes, workplaces and schools are probably a major cause of illness and death. Certainly in places where solid fuel or kerosene (paraffin) are used for cooking indoors, , hence the suspicion of harm elsewhere.

Last year, the US National Academy of Sciences (NAS) , which spelled out the huge gaps in our knowledge and said that filling them was a national priority. Other countries are doing the same, says Mandin. 鈥淚ndoor air pollution is having a moment.鈥�

As this research gathers pace, and the true scale of the problem emerges, it is tempting to conclude that there is nowhere safe left to breathe. But the good news is that we can all cut exposure to indoor pollution by making a few simple changes.

As with all things to do with toxicity, the risks depend on exposure and dose. Exposure to toxins indoors is a problem partly because most of us spend the vast majority of our time inside. An average person in the US spends . The doses we get indoors are often higher too: not least because, as covid-19 taught us, indoor nasties are less likely to dissipate, which makes it more likely that we will breathe them in.

Causes of indoor air pollution

The idea that the air indoors can be as bad or worse than outdoors first came to light in the early 1980s, when the occupants of new buildings started complaining of a range of persistent health problems such as headaches, coughs and sore throats. In 1986, the World 午夜福利1000集合 Organization (WHO) coined the term 鈥渟ick building syndrome鈥� and research into its causes got under way.

The answer turned out to be polluted indoor air, often due to poor ventilation, furnishings releasing toxic chemicals and a lot of smoking. Six pollutants were fingered as the main culprits. Five of them were: tobacco smoke; carbon monoxide from faulty or poorly ventilated gas appliances; radon gas, from the natural decay of uranium, thorium and radium deep underground; and a pair of common industrial chemicals, trichloroethylene and benzene. These two substances come under the banner of volatile organic compounds (VOCs), so-called because they evaporate readily at room temperature and so leach out of everything from paint to furniture to flooring and electricals. The sixth offender comprised particles with diameters of less than 2.5 micrometres (known as PM2.5), tiny airborne agglomerations of organic chemicals, soot, metals, soil and dust.

Some of these pollutants, notably tobacco smoke, have become less of a problem since the 1980s, at least in public spaces in some countries. But better sampling and analytical methods mean we now know more about what is in the air we breathe, and the list of nasties has just kept growing. Synthetic dyes known as azo dyes 鈥� which are used in everything from clothing to mattresses and some of which have been shown to be toxic, carcinogenic and bioaccumulative 鈥� are one notable addition, along with many more VOCs and ever finer particles. The smallest of these, called ultrafine particles, measure 0.1 micrometres in diameter and are small enough to cross from the lungs into the bloodstream and settle in organs, triggering inflammation. In the heart and brain, they . Even dust, which is mostly biological gubbins like dead skin cells, hair, fibres, pollen and mites, can trigger an immune reaction when inhaled and can act as a carrier of VOCs and other chemicals.

It is enough to make you want to crack open a window. But that needs some consideration. Outdoor air can bring in a constant payload of particulates, nitrous oxides and VOCs from traffic exhaust, , which is formed when nitrous oxides react with VOCs in the presence of sunlight. Ozone is a key player in indoor air quality, as it attacks otherwise innocuous compounds such as fragrance molecules and turns them nasty. 鈥淲e know that indoor ozone drives lots of chemistry, and that chemistry leads to the formation of pollutants indoors, some of which are harmful to health, like formaldehyde,鈥� says Nicola Carslaw at the University of York, UK.

The effect of indoor air pollution

In response to a growing awareness of the threat of indoor pollution, for exposure to five of the most common VOCs found in buildings, along with other common pollutants including carbon monoxide and radon. But the full burden of indoor pollution remains up in the air. 鈥淭here鈥檚 literally thousands of chemicals that might exist in the indoor environment, and for many of those chemicals, we have very little information regarding their toxicity,鈥� says David Dorman at North Carolina State University, lead author of the NAS report.

For those we do know about, there is good reason to sound the alarm. One VOC of particular concern is the industrial solvent trichloroethylene (TCE), found in glues, varnishes and cleaning fluids. that has been linked to brain, liver and kidney damage with high or long-term exposures. Most of the studies so far have been done in industrial workers exposed to high concentrations due to their job. Less is known about the effects of low or occasional exposures, but the WHO guidelines advise caution, stating that, since there is sufficient evidence that TCE is a genotoxic carcinogen (a chemical that may cause alterations at the genetic level), 鈥渁ll exposures indoors are considered relevant and no threshold can be determined.鈥�

It is a similar story for acrolein, a molecule produced by gas stoves, wood burners, deep fat fryers and by regular and electronic cigarettes. Studies suggest that sustained exposures . Emissions from heated oil when cooking in unventilated kitchens has been linked to an increased risk of lung cancer. And an analysis that combined the results of many studies found that exposure to benzene indoors, from cigarette smoke or the infiltration of vehicle exhaust fumes, increases the risk of leukaemia, asthma and low birth weight: the higher the concentration, the higher the risk.

In general, though, we know very little for certain about the specific disease risks, but it is likely that indoor air pollution is taking its toll, says Mandin. A rise in asthma cases has been linked to outdoor pollution, so it makes sense that some cases can be attributed to indoor pollution. Mandin also suggests that it could be part of the explanation for unexplained migraines, and even some reproductive challenges. As yet, we can鈥檛 be sure. The knowledge gap on the burden of disease caused by all this is so frustratingly wide that leading journal Indoor Air recently put out an .

So far, epidemiological research has proved difficult to do. 鈥淔or outdoor air quality, you have one monitoring station and it represents the exposure of thousands of people. But for indoor air quality, each school, each classroom, each dwelling, each office is different,鈥� says Mandin. Something similar can be said for location: depending on where you live and how fresh the air is outside, the relative risks of indoor air vary considerably.

How to improve indoor air quality

While we wait for a fuller picture to emerge, it seems sensible to reduce exposures as much as possible. Fortunately, there are a few easy ways to do this 鈥� at least at home, where we have the most control over our environment.

First up is cooking, which the NAS report calls 鈥渙ne of the most notable sources of indoor chemicals鈥�. The exact composition of the fumes depends on what you cook and how you cook it. Gas burners are the most polluting heat source, and dioxide and nitrogen oxides, which can accumulate without adequate ventilation.

As a rule, frying is more polluting than boiling or steaming, which produce mostly water vapour. Frying releases aldehydes and polycyclic aromatic hydrocarbons (PAHs) from the cooking oil and particulates from whatever you are frying. Meat can be an especially rich source of particulates, says Carslaw.

There are some signs that fumes from cooking meat could do more than just make us wheeze. Researchers at Nazarbayev University in Kazakhstan . Measurements of their brain activity with an electroencephalograph, or EEG, showed that, at peak exposure, it resembled that seen in people with a neurodegenerative condition. Activity did return to normal after 30 minutes, but the researchers warned that chronic exposure may cause long-term damage.

Frying or griddling less and boiling or steaming more is an easy way to reduce these kinds of exposures. Another easy option is to always use an extractor fan, if you have one. 鈥淚 think a lot of us will never cook again without turning our fans on,鈥� says Vicki Grassian at the University of California, San Diego, speaking for the co-authors of the NAS report.

Outside the kitchen, it might be a good idea to leave wood burners and open fires unlit, and avoid scented candles, air fresheners and other superfluous smellies. 鈥淧eople think that air fresheners, incense and essential oils are good for indoor air quality, that they will clean the air and degrade pollutants, but no, they emit pollution,鈥� says Mandin.

House plants have a reputation as air cleaners, but research suggests that most homes would need thousands of them to make a difference. Good ventilation, however, works well, reducing the concentration of pollutants generated indoors. It does invite ozone in, but unless you live on a busy road, on balance, fresh air has a positive effect, especially when the sun isn鈥檛 shining and ozone production is low. Air-scrubbing technology such as HEPA (high-efficiency particulate air) filters and air conditioning units can help, but are expensive. A cheaper fix is to buy a device to measure air quality (see 鈥淪hould I buy an indoor air quality monitor?鈥�), which can be had for less than 拢100, and hotfoot it from spaces where the pollution is bad.

And don鈥檛 overdo the cleaning. Dusting and vacuuming resuspend dust, creating an inhalation hazard. Use a wet cloth rather than a dry duster or vacuum cleaner, Mandin suggests. Choose cream cleaners and roll on deodorants instead of sprays, too.

It is also a good idea to leave any new furniture and furnishings in a well-ventilated space for a few days before putting them in position. 鈥淣ew furniture will emit a lot of volatile organic compounds,鈥� says Mandin.

Nevertheless, some level of indoor air pollution is inevitable and we shouldn鈥檛 jump to the conclusion that we are being poisoned in our own homes, says Dorman. 鈥淭here are research needs and scientific gaps in our knowledge, but that doesn鈥檛 necessarily mean that everybody is at some great risk,鈥� he says.

These gaps are being filled all the time. New methods that allow scientists to sample an environment and capture all the chemicals it contains are providing a clearer image of what is in the air. using this approach in a gymnasium, formed from a reaction between amino acids in sweat and a bleach used to clean the exercise equipment. A similar technique found that the antibacterial triclosan is ubiquitous in indoor air. 鈥淲hen we were not able to measure it, we thought it was only in toothpaste,鈥� says Mandin. Other recent discoveries include those azo dyes, plastic additives called ultraviolet stabilisers, the herbicide glyphosate in dust, and compounds from detergents that are released when clothes are dried on a radiator. As the list keeps growing, so do the known unknowns.

Another research challenge is to work out how different chemicals mingle and react with each other. 鈥淲e鈥檙e being exposed to multiple chemicals simultaneously in the indoor environment and we have chemical-chemical interactions that are not fully understood,鈥� says Dorman.

There may still be much to learn, but just like sick building syndrome triggered a flurry of discoveries, covid-19 has also put a burner under research into indoor air quality. 鈥淚 think it鈥檚 a new dawn,鈥� says Dorman. 鈥淲e鈥檒l know more in 10 years than we do now.鈥� In the meantime, if you need a rule of thumb, think 鈥渧entilation, ventilation, ventilation鈥�.

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