Posts Tagged ‘smoking during pregnancy’

Few newborns are already capable of mounting an allergic reaction to dust mite. Actual symptoms of allergy may not appear for several months or years, but the essential first

step – making the allergy antibody, IgE, against the mite allergens – seems to have occurred already for some babies.
In situations where IgE does the job it is supposed to do –protecting against worms and other parasites (see p. 13) – this advance programming of the immune system before birth

has definite advantages. A child whose mother is infected with parasites is born with the ability to make IgE against those parasites, even though he or she has had no direct

contact with them before birth. The baby’s immune system has been forewarned of the likely hazards of life in the outside world.
While this is obviously valuable in conditions where parasitic infections are rife, emerging into a carpeted and well-upholstered world with IgE against dust mite already in the

bloodstream is a serious disadvantage, because it can pave the way for rhinitis and asthma. Given the trouble caused by dust-mite allergen, some doctors think that women should

try to reduce their exposure to it during the second half of pregnancy, so that little or none reaches the unborn child. At present it is not known for sure if this can make a

difference to the risk of allergies developing in a child, but it seems plausible.
What is pretty clear, from several previous studies, is that the level of house-dust mite in the home immediately after birth can make a distinct difference as regards the

chance of allergy developing. Minimising a newborn baby’s exposure to dust mite is worthwhile, and the measures needed to achieve this are described on pp. 244-5.
Carrying out these measures will raise the level of dust-mite allergen in the air temporarily, so it makes sense to do the work in the early stages of pregnancy (or – even

better – before conception), rather than expose yourself and the foetus to a tremendous burst of allergen later on in pregnancy. Or, get someone else to do the work, and stay

away while it is done.
There may be other potential allergens which you should try to eliminate from your home before the baby arrives, such as mould allergens (see p. 122).
Pregnancy
First and foremost – don’t smoke while you are pregnant, or afterwards (see box on p. 107). Any other smokers in the household should smoke outdoors.
What about your diet during pregnancy? Certainly you should eat a good balanced diet with plenty of fruit and vegetables. Taking a small supplement of vitamin E, or eating

plenty of sunflower seeds and oil, would be a good idea. Women with a low
intake of vitamin E and antioxidants (see p. 206) during pregnancy run a higher risk of having an allergic child.
Should you also avoid any foods? Food allergens, such as those from cow’s milk, do reach the foetus, passed from the mother’s blood to the baby’s blood via the placenta. And a

few babies are born already capable of making IgE against food allergens. On the basis of these findings, some doctors have suggested that avoiding potentially allergenic foods

(such as eggs, cow’s milk and peanuts) during pregnancy might help to reduce the risk of food allergy. However, evidence from research trials in which pregnant women followed a

restricted diet, and their children were later studied for allergies, does not show any convincing benefit. And in some studies, the women on restricted diets have not gained as

much weight as they should, and the babies have been slightly below average weight at birth. Most doctors now think that dietary restrictions during pregnancy are not worthwhile

– it is more important to eat well and get enough nutrients.
It does seem sensible not to overeat any particular food during pregnancy, although there is no scientific evidence on this point (simply because researchers have not yet looked

for such evidence). In particular, don’t overdo it with milk and milk products. Make sure you get enough calcium, obviously, but don’t force yourself to drink huge amounts of

milk, especially if you have any distaste for it. Talk to your doctor, midwife or health visitor about the possibility of a calcium supplement, if you dislike milk.
Breast-feeding
‘The cornerstone of allergy prevention is breast-feeding,’ according to Dr Erika Isolauri of Tampere University Hospital in Finland.
At one time, this would have been a controversial statement, but there is now a substantial body of scientific evidence to support the ‘breast-is-best’ idea in relation to

allergy prevention. A number of different studies have shown that exclusive breast-feeding, up to at least four months of age, reduces the risk of developing food allergy or

atopic eczema (or both) in the early years of life.
Exclusive means exactly that – no solids at all until after four months (and six months is better), and no supplementary feeds with infant formula, which is made from cow’s

milk, and therefore contains cow’s milk allergens. Unfortunately, it is sometimes far from easy to ensure that formula feeds are not given just after birth, by well-intentioned

nurses on the maternity ward. Given what we now know about the immune system of the newborn, this is the worst possible time to be delivering an onslaught of potentially

allergenic cow’s milk proteins.
Quite apart from the immediate effect of introducing cow’s milk allergens to the baby, a bottle can disrupt the development of a good breast-feeding relationship between mother

and child, and may lead to the early abandonment of breast-feeding.
Why should this happen? Firstly a different technique is needed for sucking on a bottle teat, and your baby may never develop the knack with nipples if given bottles at an early

stage. Secondly, allaying the baby’s hunger with a bottle can also mean that he or she demands less at the next breast-feed – and since the mother’s milk supply is partly

influenced by the level of demand, this can be detrimental. Some experts believe that occasional bottle-feeds can start a downward spiral of ever-diminishing supply from the

mother.
Dr Arne Host of the Department of Paediatrics at Odense University Hospital in Denmark, who has made a special study of breast-feeding, recommends giving a little boiled water

as a supplement during the first 3-4 days of life, if the breast milk supply is inadequate. After that time, the mother’s own supply should increase to meet the needs of her

baby. Introducing bottle-feeds at an early stage can prevent this delicate balance of supply-anddemand from ever being achieved.
Sometimes (though this is rare) despite everything being done just right, a mother’s supply of milk never quite matches her infant’s appetite. When this happens, and the child

concerned is from an allergy-prone family, the breast milk should be supplemented with an ultra-safe formula feed called a hydrolysate (see box on p. 66).
Hydrolysates should also be used for infants at high risk of allergy who, for whatever reason, cannot be breast-fed. Note that there are two categories of hydrolysate –

extensively hydrolysed formula and partially hydrolysed formula. For the purposes of allergy prevention, an extensively hydrolysed formula should always be used because it has

the lowest risk of causing food allergies.
Preparing to breast-feed
Because breast-feeding is natural, many first-time mothers just assume it will come naturally. Sadly, it often doesn’t.
Cracked nipples are a major obstacle. They are the equivalent of chapped hands, and are often caused by the baby not having ‘latched on’ correctly to the nipple. Help from an

expert breast-feeding adviser, right from the start. can avoid this problem.
Because cracked nipples are so sore, breast-feeding can then become a major ordeal rather than a pleasurable experience as it should be. What is more, infectious bacteria can

enter the breast through the cracks in the skin, causing mastitis, which is painful and may require antibiotic treatment: this is not necessarily a good thing for the baby (see

p. 247).
You can minimise the chance of cracked nipples by making the skin on the nipples tougher and more resilient, so that it does
not crack. Start during pregnancy, in about your fourth month. When you have a bath or shower, rub your nipples vigorously with your flannel for a few minutes. After three weeks

of this, graduate to a soft toothbrush, and brush them gently, then more firmly when they feel ready. Progress to a medium, and then a hard toothbrush.
Breast-feeding support groups can be immensely helpful, when you start breast-feeding, or when you feel things are not going right. Some groups have local advisers. all mothers

themselves with first-hand experience of breast-feeding. Having such an adviser with you, watching you breast-feed your new baby and making suggestions, or pointing out where

you are going wrong, can make all the difference. Look for such a group locally, and establish contact with them well before your due date. You may be able to have an adviser

with you at the birth, to help the baby take his or her first feed: this is of enormous value.
Having prepared yourself, you then have to prepare the nursing staff in the hospital where you will give birth, for the fact that you want to breast-feed exclusively. That means

no supplementary feeds from the staff – not even one bottle. The risks of this practice, in sensitising vulnerable babies to cow’s milk, are still not widely known, so you may

need to be persistent and make your feelings very clear. Talk to your midwife about this well before your expected delivery date, and find out what policy the hospital has about

supplementary feeds. Then see the relevant staff at the hospital.
The nurses are most likely to give the baby a bottle because he or she is crying while you are asleep, and they don’t want to wake you. Staff change all the time, so you will

probably need to put a notice on the crib or cot, to be certain that the baby is never bottle-fed while you are sleeping. If this seems ‘over-the-top’, consider the experience

of British researchers investigating allergy prevention who wanted to ensure that a group of newborns were never given supplementary feeds. They put warning stickers on both the

babies’ cots and the mothers’ beds, as well as asking the midwives and mothers to be very vigilant. Despite this effort, several of the babies being studied were given bottles.
Sometimes nurses give a bottle because they believe that the baby is not getting enough milk from the breast. The idea that mothers “don’t have enough milk”, and that this is

quite a common problem, is part of the medical folklore of breastfeeding today. In fact, true milk insufficiency is very rare. Most cases of poor milk supply arise because a

good breastfeeding relationship between mother and child is never established – and supplementary bottle feeds are partly to blame.
It is entirely possible that your milk supply will not be quite adequate in the first few days, but it should increase rapidly. The best thing, if breast- milk supply is

inadequate, is to give boiled water as a supplement during the first 3-4 days of life (see left).
Some preliminary evidence suggests that mastitis may alter the profile of immune cells in the milk, and that this might possibly increase the risk of the child’s own immune

system becoming allergy-prone. A key preventive measure is not to let the breasts become engorged with milk: the build-up of milk can lead on to mastitis. Learning to express

milk (by hand or with a breast pump) will be useful for times when your breasts feel over-full. Talk to a breast-feeding adviser.
Diet during breast-feeding
Pretty much everything you eat works its way into breast milk, though in very tiny amounts.
The food molecules that get through into breast milk can certainly affect babies who are already sensitised to a food. Cow’s milk is the classic example — cow’s milk proteins

get into human milk if the mother consumes any milk, cheese, yoghurt or other milk products. Babies who have already been sensitised to cow’s milk (by a supplementary

bottle-feed, for example, or even in the womb — see p. 241) react badly to the breast milk, unless the mother avoids all dairy products.
What is less certain is whether the traces of allergen in breast milk — cow’s milk allergen or that from any other food — might be capable of starting off allergy or

sensitivity. Are these minute traces enough to sensitise babies with a strong tendency to allergy? If they are, then mothers of high-risk infants might be well advised to avoid

certain allergenic foods while breast-feeding. Some studies do suggest that there is a reduction in food allergy if breast-feeding mothers avoid cow’s milk, eggs, nuts, fish and

soya. But if this restrictive diet makes your life impossible, then it is better to breast-feed your baby and eat what you like, than not to breast-feed at all.
Unfortunately, some babies do get eczema, in spite of being exclusively breast-fed. If this happens with your child, there are a number of steps you can take to deal with the

problem (see box on p. 248).
Treating the gut flora
Taking a probiotic or bacterial replacer (see p. 205) during the later stages of pregnancy, and continuing with this while breast-feeding, may reduce the risk of atopic eczema

in your child.
Weaning — when and how
The key to reducing the allergy risk for babies is to turn that old political jibe ‘too little, too late’ on its head. Research shows that, with weaning, it is ‘too much, too

early’ that increases the chance of allergic reactions developing. Suddenly presenting an infant of three months with a wide variety of solid foods, including potent allergens

such as eggs, peanuts and fish, can increase the likelihood of food allergy and/or eczema developing. Weaning late, with a limited number of safe foods, should be your goal.
At least four months of exclusive breast-feeding, and preferably six months, is now the standard recommendation for allergy prevention, and it is well supported by scientific

evidence.
But how long should breast-feeding continue after weaning begins? There is little concrete evidence here, but there is a strong belief in the medical community that

breast-feeding should go on for several more months, up to or beyond one year of age if possible, allowing the weaning process to be very gradual. The idea is to introduce new

foods one at a time, alongside breast milk.
As well as allowing the baby’s immune system lots of time to adjust to each new food, prolonged breast-feeding may help in another way as well. Recent research shows that breast

milk contains a great many substances which influence the baby’s immune system, nudging it in the right direction — away from any tendency to allergies.
Avoid those expensive little jars of ready-made baby food. Most contain potent allergens such as cow’s milk, wheat or soya. Making your own baby foods is not difficult, and is

the best way to ensure that your child gets only low-risk foods.
Reducing the risk of peanut allergy
Peanut oil, which contains traces of peanut allergen, is an ingredient of some skin creams. Recent research from the United States shows that babies treated with such creams

were seven times more likely to develop peanut allergy later. In the past, concern has focused on traces of peanut allergen that the baby swallows — either in the breast milk

(because the mother has eaten peanuts) or from her nipple cream. What this new research suggests is that peanut allergens absorbed through the baby’s skin are much
more likely to cause sensitisation. Don’t use any skin products if they have ‘Arachis oil’ or ‘Arachis hypogaea’ in the ingredients list — and steer clear of any cream without a

detailed ingredients list. In the same research study, soy formula also emerged as a risk factor: feeding a baby on this doubled the chance of peanut allergy developing later.

Good health is one of the most important things we can give our kids,’ says Martha, now in her sixties with two grown-up children.
`When I see how bad my daughter’s asthma is, and how hard her life is sometimes because of it, I do feel bad about the fact that I smoked when I was pregnant. But we just didn’t

know in those days. Even my doctor smoked. No one thought anything of it.
`I stopped when she was little, because it seemed to me that her wheezing got worse whenever I lit up. I’m sure that stopping then was better than nothing. It must have helped.
`In any case, there’s no point feeling guilty about things now - that won’t change anything. But if I’d known what damage it could do, I would have stopped sooner.’ Martha’s

regrets stem from the discoveries made in the past decade about the effects of smoking on allergies. We now know that smoking during pregnancy increases the amount of IgE (the

allergy antibody) in the blood of a newborn baby - an indication that he or she is at an increased risk of developing allergies. After the birth, exposing a child to cigarette

smoke continues to encourage high levels of IgE in the blood, as well as irritating the airways and making asthma more likely to develop.
The research on smoking is just one part of a worldwide research effort, during the past 20-30 years, into the possible causes of the allergy epidemic. That research can help

parents who are themselves atopic (allergy-prone) to reduce the risk of passing their allergy problems on to their children.
Who should be implementing these preventive measures? Firstly, any prospective parents who have allergies themselves, or had them as children. They are at higher risk (compared

to a non-allergic parent) of producing a child who is susceptible to allergies. The risk is especially high if both parents have or have had them at some point in their lives.
Secondly, these preventive measures could be worthwhile for parents who don’t have allergies themselves, but who come from atopic families (families with a tendency to allergy).

If you or your partner have brothers, sisters or parents with allergies, you are more likely than the average person to produce allergic children.
Finally, if you already have one allergic child - even though you and your partner don’t have allergies yourselves, and no one else in the family does - there is a

higher-than-average chance that subsequent children will have allergies. Your allergic child is a sign that the genes for allergy are there.
Given the important role that genes play in allergy (see p. 8), preventive strategies make a lot of sense for parents-to-be with allergies in the family.
Unfortunately, this is a topic which often generates confusion - some people assume that if a trait is genetic, it will inevitably come out in the child, and that nothing can be

done to prevent this happening. Although that is true for some inherited traits, such as metabolic abnormalities (see upper box on p. 75), it is not at all the case for allergy.
Developing allergic disease is not inevitable unless a child has a very big dose of the genes that favour allergy. Only a few children - generally those whose mother and father

are both badly affected by allergies - will come into this category. Even with these very high-risk children, following the measures described here will probably help to reduce

the severity of their allergic problems.
For most children at risk of allergies, even though they have some pro-allergy genes, there has to be an unfavourable environment to actually produce allergic disease.

‘Environment’ here means everything external that affects the child, including diet, air quality, allergens, diseases and medical treatment. Factors occurring before birth, such

as the mother’s lifestyle during pregnancy, are also part of the child’s environment. It is the interplay between genes and environment that will decide whether your child

develops allergies or escapes them.
This interaction is not a simple one, however, and different aspects of the environment operate in different ways. Firstly, there are some environmental factors that work at the

most fundamental level -conspiring with the pro-allergy genes to make the overall tendency to allergy far stronger. These are factors such as cigarette smoking by the mother

during pregnancy, or excessive hygiene during childhood, which influence the fundamental make-up of the child’s immune system. Secondly, there are environmental factors, such as

early exposure to house-dust mite or grass pollen, which can cause trouble by provoking specific allergic reactions. Note that factors like these will not become important

unless the allergic tendency is already there.
Efforts to reduce the risk of allergy operate on both types of factor.
On the one hand, there are measures such as quitting smoking or easing up on hygiene, which tackle the allergic predisposition itself. These measures are, in effect, trying to

make a Western child’s immune system more like the immune system of a child from a poor rural village in the developing world, whose chance of developing allergy is very low

indeed.
On the other hand, there are measures such as reducing dust-mite levels, that try to stop the development of particular allergic reactions.
Obviously, if measures of the first kind could be truly successful, there would be little or no need for measures of the second kind. But this kind of success is very difficult

to achieve in modern Western society. Although we can certainly improve matters a great deal, and lessen the tendency to allergy, the conditions that would completely reverse it

are beyond our reach at present. So both kinds of preventive measure remain necessary.
In reading the pages that follow, it is important to keep things in perspective, and not feel excessively anxious about your child. Do what you can, but don’t feel guilty if you

can’t manage everything that is suggested here. And if you already have a child with allergies, please don’t feel guilty about things that might have contributed to this. Only

hindsight is perfect, and you no doubt did the best you could, given the information you had at the time, and the many other constraints and difficulties that you faced. That is

the best that any of us can do.

Air Pollution and Allergy

Air pollution plays a variety of roles in allergic reactions. Some pollutants irritate the nose and airways (and sometimes the skin) making them more sensitive to allergens. These pollutants can worsen existing allergic symptoms and may promote the development of allergies in children, by making the airway membranes more permeable. Other chemical pollutants may affect the immune system directly, increasing any existing tendency to allergic reactions.
Indoor pollution
For many of us, the air in our houses is much more polluted than any outdoor air. Several of the indoor pollutants irritate the nose and airways, and some can trigger asthma attacks. A few of the pollutants found indoors can also make allergies and asthma more likely to develop in young children.
Background pollution
One of the worst irritants in indoor air is tobacco smoke. Other people’s cigarette or pipe smoke can trigger asthma attacks in the short term, and makes asthmatics generally worse in the long run. Passive smoking might also affect the immune system making allergies more likely to develop, though this is not proven. Do whatever you can to eliminate tobacco smoke from your home.
Everyone is different
This article considers air pollution from the point of view of someone with classical allergies (e.g. hayfever or asthma). Those with chemical intolerance (see p. 84) may well be more severely affected by air pollution.
If you smoke yourself, there are many good reasons for giving up:
• If individuals from atopic families (see p. smoke, they have a far greater chance of developing allergies and/or asthma when exposed to an allergen in the air.
• For those who had asthma as children and have since grown out of it, cigarette smoking doubles the chance of it coming back.
• Parents of asthmatic children who smoke indoors make their children’s asthma worse. Teenagers can be just as badly affected by passive smoking as young children.
• Smoking during pregnancy significantly increases the risk of a woman’s baby developing allergies and asthma. (Smoking also leads to more prematurity, still-births and cot deaths.)
If possible, have an electric cooking stove rather than a gas one –or fit a powerful extractor fan. Cooking with a gas stove generates a lot of nitrogen dioxide, a gas that you can’t smell or see but which affects the airways. This same gas also comes from motor traffic, but peak levels of nitrogen dioxide in kitchens with gas cookers are often ten times the average level on city streets, and frequently exceed standards for outdoor air set by the world Health Organisation. Other sources of nitrogen dioxide include cigarettes, gas fires and kerosene-burning stoves.
For some people with allergies, nitrogen dioxide enhances their response to the allergen. So if you inhale dust-mite allergen together with nitrogen dioxide, it may have more effect than the Smoke screen
Smoke particles from coal or wood do not seem to make allergies more likely to develop - in fact, quite the reverse. In rural areas of Germany, researchers have found that children with coal or wood stoves in their homes were less likely to have allergies or asthma. An Australian study made a similar finding. Bronchitis and pneumonia are more common in those children with wood and coal stoves and these infections may stimulate the immune system in such a way that allergies are less likely to develop later. However, wood smoke may be a cause when asthma begins in an adult.
allergen alone. Breathing sulphur dioxide (see below) and nitrogen dioxide together boosts the reaction to allergen more powerfully than either gas alone.
Nitrogen dioxide might also make asthma attacks more likely, but the evidence on this is conflicting.
For young children, a high level of nitrogen dioxide at home may make the development of allergic reactions more likely. A recent Canadian study showed that children exposed to high levels of nitrogen dioxide in the home - usually from gas cookers - were ten times as likely to develop asthma as those breathing low levels of nitrogen dioxide. If a dog, cat or other furry pet was kept, and there were high nitrogen dioxide levels, the risk of developing asthma shot up even higher, to 25 times that of children with low nitrogen dioxide and no pets. (Other studies have not produced the same spectacular results, but their methods of measuring nitrogen dioxide exposure were less precise.)
Try to eliminate materials that produce formaldehyde fumes, or seal the items with a good coat of paint. Formaldehyde is given off by chipboard and to a lesser extent by MDF (medium-density fibreboard). Injected cavity wall insulation can also produce persistent formaldehyde fumes, and is very difficult to get rid of -moving out is often the only option. A recent study from Australia showed that children exposed to formaldehyde, especially in the bedroom, were more likely to develop allergic reactions: the higher the level of formaldehyde exposure, the more severe the child’s allergic sensitisation.
Those with asthma have more frequent symptoms if exposed to high formaldehyde levels. A recent study from Finland shows that easy-to-clean plastic wall-covering and flooring increases the risk of asthma in children.
A Canadian study found that children whose first home was less than 20-30 years old were 50% more likely to develop asthma than children living in older houses. One possible explanation for this lies with the materials used in the construction and fitting of new houses, especially the plastics, wood preservatives and insulation materials. Solvents, and chemicals such as formaldehyde, are still being given off by these materials some years later.
Air fresheners provoke asthma attacks in some people. For a few individuals they can cause general symptoms of ill-health that are similar to those described for mild chemical intolerance (see p. 84). Those affected generally don’t realise that the air freshener is the source of the trouble. This malign effect is not entirely surprising, since air fresheners work by giving off a chemical that targets part of the brain - the part involved in processing sensory input from your nose. The chemical ‘freshens the air’ by partially disabling your sense of smell. Better to open a window.
Cleaning products, furniture polish and deodorant were never intended to go into the nose and airways, but that’s what happens when they are sprayed from an aerosol, and they can trigger asthma attacks. Steer clear of aerosols as much as possible - there are usually alternatives.
Pollution peaks
Read the instructions and ingredients lists on all products carefully. It is not just a question of what’s in them, but also what gases they might give off when used. One asthmatic died within minutes when the de-rusting agent she was using on her dishwasher produced a large amount of sulphur dioxide gas: her airways tightened up so much that she couldn’t even use an inhaler to save herself. ‘Sulphuric’, ’sulphate’ or ’sulphite’ in the list of ingredients should ring warning bells if you have asthma: sulphur dioxide gas could be given off by this product.
Bleach, and other chlorine-based cleaning products, such as toilet cleaner and scouring powder, should be used sparingly, and with plenty of ventilation. These products release chlorine gas which, in large amounts, can irritate the airways of asthmatics. Never allow bleach or toilet cleaner to become mixed with any other product. Take care with any product containing hypechlorte, chloramine, ammonia, acids or morpholine and with the chemicals used for swimming pool water. All these can trigger asthma attacks.
If doing repairs or DIY work about the house, take special care. Always ventilate the work area well, and wear a dust mask if sawing or drilling.
The smell of paint is due to solvents, and these can act as irritants to the nose and airways. When decorating, ventilate well, and use low-odour water-based paint. Some of the best low-odour paints, tested and shown to be safe for paint-sensitive asthmatics, are only available by mall order: see p. 255.
‘Instant foam’ kits sold for DIY insulation can provoke asthma in those who were not asthmatic previously. Two different substances are mixed to create the polyurethane foam, and during the mixing process, isocyanate is released – this is one of the most powerful asthmagens known (see box on p. 132). The level of isocyanate can breach the safety limit set for factories.
Avoid using fly spray or other insecticides: look for other methods of pest control. A study from Ethiopia showed that people using an insecticide in their houses were twice as likely to develop allergies. A study of Canadian farmers suggested that asthma might be linked to the use of carbamate insecticides (e.g. carbofuran). The sprays used for cockroaches can act as irritants for those with allergic rhinitis or chronic sinusitis.
If advised that your house needs spraying with insecticide, for woodworm or other wood-boring pests, ask for more information before you go ahead. Is the spraying really necessary? What will happen if the house isn’t sprayed? How quickly will it happen? Is there any other method of eradicating the pest? Spraying is often done when it is not really essential – houses remain standing even with woodworm holes all over them. Unless you have a heavy infestation that is threatening the structure of the house, you are probably better off not having the house sprayed. The heavy and ongoing exposure to insecticide that spraying of a house involves is something you and your family should avoid if at all possible. All the sprays used are toxic to some extent – don’t believe those who tell you otherwise. A heavy exposure to pesticides can sometimes make allergic symptoms worse or precipitate chemical intolerance (see p. 85).
The garage, workshop or garden shed can also be very polluted. Petrol, kerosene and paraffin can affect some people with rhinitis or asthma, and can bring on their symptoms. These fuels should always be kept in airtight containers. Paints sold for cars often contain isocyanates, among the most common causes
of work-related asthma (see box on p. 132). If using such paint, wear a mask with an activated carbon filter and make sure the area is well ventilated. Avoid prolonged or repeated exposure.
Outdoor pollution
Some of the pollutants in outdoor air can make allergic reactions worse and can trigger asthma attacks in people who are already asthmatic. A study of hospital admissions in London, Paris. Barcelona and Helsinki found that high levels of pollution increased hospital admissions for asthma by about 3%.
The pollutants that matter to those with allergies are:
• ozone, which soars to high levels on sunny days, mainly in country areas that are near large cities. The reason for this is a chemical reaction which occurs when car exhaust fumes are exposed to sunlight, producing ozone, a highly reactive form of oxygen. Further chemical reactions, involving another ingredient of exhaust fumes, then break the ozone down again. Thanks to this second reaction, there is usually little ozone in city air. But in a relatively rural area 20 miles or so upwind of the city, the pollutants are too dispersed for the second reaction to occur, and the ozone from the urban traffic can accumulate.
Ozone levels in the air tend to peak in the late afternoon and early evening – but it takes 4-24 hours for ozone to produce its effects on the airways. Indoors, ozone breaks down very quickly because of contact with other gases inside the house.
Ozone can increase the effects of allergens, such as pollen, on the nose and airways.
In addition, ozone makes the airway muscles contract, even for people without asthma. Healthy people tend not to notice these effects, whereas some asthmatics may have more symptoms, and may need more drugs, on days when ozone levels are unusually high.
• diesel particulates, which can become a problem in town centres, and close to main roads used by vans and lorries. Unlike ordinary petrol, diesel fuel contains oil, so when it burns it produces tiny black particles. These consist of flakes of carbon (soot), coated with complex chemicals that are produced by the
But what about the ozone layer…?
Is ozone good for us or bad for us? People often get confused about this, because of all the discussion about
‘the destruction of the ozone layer’. But that ozone layer (which screens us from harmful ultraviolet light) is a natural phenomenon and it is thousands of feet up, well away from our lungs. At ground level, in the air we breathe, ozone is unnatural and potentially damaging .
The size of the particles
Diesel particles are 1-10 microns in size, with most smaller than 2.5 microns. Tobacco smoke, coal smoke, fumes from oil-burning boilers, and the smoke from frying food all contain very much smaller particles, down to a hundredth of a micron (.01 microns) in size. (A micron is a thousandth of a millimetre.)
In pollution reports, counts for particles in the air (mostly diesel particles these days, except in heavily industrialised areas) will often appear as ‘PM1 0′, meaning ‘Particulate Matter less than 10 microns in diameter’. This particle size is chosen because larger particles tend to settle in the nose and throat, and not reach the airways of the lungs. The term ‘Small Particles’ is sometimes used to mean PM10.
To deal with air pollution, you need a really good mask with two filters: a dust filter that can take out very small particles and an activated carbon filter that absorbs irritant fumes and gases. Note that while activated carbon filters remove most pollutants, they do not take out nitrogen dioxide unless they have been specially treated.
partial combustion of the oil. It is probably these surface chemicals, rather than the soot particles themselves, that have such bad effects on the nose and airways.
Some research suggests that diesel particulates might increase the risk of allergies developing – to pollen for example. Additionally, when levels of diesel particulates are high, asthmatics tend to have more symptoms. If levels rise above 50 micrograms per cubic metre there is a sharp increase in asthma attacks – and a recent study in Birmingham showed that such levels are regularly reached at roadsides.
• sulphur dioxide, which often reaches high levels in areas of heavy industry, particularly near coal-fired power stations and coking plants. It acts as an irritant to the airways and can trigger attacks in asthmatics, who are far more sensitive to sulphur dioxide than healthy people (see box on p. 207). However, at the sort of concentrations normally encountered, even in quite polluted air, sulphur dioxide does not have any effect on most asthmatics.
• nitrogen dioxide, which is produced by all types of vehicles, and by power stations and some factories. In towns and cities with heavy traffic, nitrogen dioxide can build up to high levels. This gas is also found indoors (see p, 128) – often at far higher levels.
Oil refineries and cement works
In addition to these widespread pollutants, there are localised areas of air pollution, around industrial sites, that are frequently accused of causing health problems, including high rates of asthma. The kinds of industrial sites regularly mentioned include:
• oil refineries and oil-burning power stations
• cement works that use waste solvents for fuel
• dock areas where oil is loaded into tankers.
None of these accusations has been investigated in any detail, so it is impossible to say if there is a real link with asthma.
Avoiding outdoor air pollution
If you live in the kind of area that experiences high levels of ozone (see p. 130), plan your outdoor activities, especially jogging or playing sport, to avoid summer afternoons and early evenings.
Those who live very close to a main road, with a lot of lorries going past, would probably improve their own health, and reduce the chance of their children developing allergies and asthma, by fitting air conditioning or high-quality HEPA air filters – or by moving house. However, the benefits, in terms of decreased risk, are not enormous, and it is important to take other preventive measures as well (see Chapter 8).
When driving, if you stop behind a lorry or bus, keep your distance, close the window and turn off the fan. Diesel vehicles often emit a thick cloud of particles as they set off, and this can come straight into your car, setting off severe attacks for some asthmatics.
A car with air conditioning will reduce your exposure to diesel particulates while driving. When buying a new car, you can make a contribution to air quality by choosing a non-diesel vehicle, preferably one with a catalytic converter fitted. Alternatively, buy a diesel vehicle with a particle filter on the exhaust (now fitted as standard in Germany).
In Britain, the Vehicles Inspectorate of the Department of Transport encourages the public to report lorries and buses seen pumping out black smoke (look in the phone book for the number).
If you are asthmatic, breathing through your nose may help as this can filter out some damaging pollutants before they reach the airways in your lungs. (If your nose is usually blocked, try the exercises on pp. 230-31).
When levels of ozone or sulphur dioxide are high, taking a supplement of Vitamin C and eating plenty of foods that contain Vitamin E and beta-carotene (see p. 207) can protect your airways.