This blog often talks about risks that we fret over too much. Time to talk about one we worry about too little; the air we breath…indoors. For a number of reasons, indoor air pollution is probably a greater overall risk to our health than the outdoor kinds that get most of the attention.

            First of all, we’re inside most of the time. Nine breaths out of every ten we take, we take inside our home, or work place, or in stores or educational or recreational or medical facilities, etc..

            Second, either to save energy or out of just plain laziness, we don’t ventilate buildings very well. So the levels of potentially hazardous pollutants in the limited volume of air inside, build up. And poor ventilation means that humidity levels can be either abnormally high, or low, which can make the hazard worse.

            Third, consider the stew of what indoor air pollution includes. The air we breath is loaded with what Edward Wilson, in Diversity of Life, refers to as aeolian plankton, the mix of all sorts of stuff carried along by the current…in this case the air, not the water. Every breath you take inside contains LOW DOSES of some (many, actually) of the following;

–  Biologicals. Bacteria, viruses, fungi, mites, molds, allergens, animal dander…all sorts of tiny wind-borne wildlife. (There is a fun science piece on this in the NYT, Mapping the Great Indoors)

–  Industrial chemicals. Tiny doses from building materials and insulation and plastics and glues and carpets and furniture and paint and cleansers and soaps and cosmetics and insecticides and all sorts of consumer products.

–  Environmental tobacco smoke (ETS, or second-hand smoke).

–  Carbon monoxide and nitrogen dioxide from the inefficient burning of fossil fuel.

–  Radon. This naturally occurring radioactive gas seeps into basements and foundations from the soil wherever the bedrock contains grains of the element uranium. (One area with a high concentration of uranium in the bedrock, and thus high radon levels in homes, is around the Three Mile Island nuclear plant in Pennsylvania. Radon levels in many buildings there are higher than anything that was released during the meltdown.)

–  Asbestos

–  Outdoor air pollution. If it’s outside, some of it is inside. Particulates, smog, industrial chemicals known as ‘air toxics’. 

     And that last category, outdoor air pollutants, raises a really interesting point. There are plenty of regulations controlling our exposure to these pollutants when we are outside. There are practically none, for the same stuff, as soon as we go inside. Schools are covered for some things (asbestos). Public buildings and work places are covered for some things (ETS). Homes are covered for a few things (radon). Hospitals are required to filter the air to control the spread of germs. But effectively, the regulation of indoor air pollution is minimal.

            Why? In part because a risk we take voluntarily worries us less than one that is imposed on us, and because a risk we are unaware of scares us less than one that’s in the headlines or that advocates campaign about, and because a lot of what is in our indoor aeolian plankton is natural – even radon – and natural risks scare us less than human-made ones. (An easy way to become more aware of this risk is to go into a dark room with a flashlight, and watch the aeolian plankton that floats across the beam of light. You’re inhaling that stuff all the time!)  With little public concern, there is less pressure on government to regulate this risk, or even to invest in the basic research to identify the specifics of the risk in the first place.

            Before you run out an buy a gas mask, remember that there are many elements that determine how risky something is. Just because you’re exposed to something doesn’t mean it’s hazardous. And even if it is hazardous, the dose you’re exposed to matters. And even if you’re exposed to potentially dangerous levels, the level of danger varies widely too. So just how much danger is posed by indoor air pollution varies widely. It is rare that the levels of indoor air pollutants are high enough to pose an immediate threat (what scientists call an acute risk), like when a furnace fails and carbon monoxide levels build up to potentially fatal levels. Mostly, indoor air pollution is known as a chronic risk, a danger posed by repeated exposure to low doses over a long period of time. But there is a long list of potentially serious harm this sort of air pollution can do.

            Also remember that the risk of indoor air pollution is relatively easy to reduce. Open a window. Turn on a fan. Ventilate. A huge part of the risk of indoor air pollution comes from the failure to mix fresh air with the air that’s been caught inside. (This is a big part of why schools have some of the worst levels of indoor pollution of any class of building. To control temperatures and save energy/money, windows are kept closed and fans aren’t run. And in school systems with tight budgets, building maintenance is a low priority, so fan filters aren’t cleaned, and leaky roofs allow dampness and mold to build up.)

            Other specifics about the risk of indoor air pollution, including more details on the harms it does and ways you can reduce the risk, are described in the chapter on this issue in RISK, A Practical Guide for Deciding What’s Really Safe and What’s Really Dangerous in the World Around You, which I co-authored with George Gray. That chapter offers more detail and is attached at the end of this piece.

            Happy breathing!

Indoor Air Pollution

We spend 90 percent of our time indoors. Whether at home, at work, at school, in stores, medical facilities, recreational facilities, or in some sort of vehicle for transportation, we’re inside most of the time. So the quality of the air we breathe indoors is in many ways more relevant to our health than the air we breathe outdoors. Our exposure to air pollution  – the concentration of pollutants per unit of air, multiplied by the time we’re exposed to that air – may be 10 to 50 times higher indoors than outside. Many public health experts say indoor air pollution is one of the biggest environmental risks we face. Yet it is one of the least studied, most poorly regulated areas of public health.

The Hazard

            Indoor air pollution is not just a hazard because we’re inside a lot. For a number of reasons, concentrations of pollutants can be higher indoors than out. Compared with the outdoor environment, the indoor environment has a limited volume of air, so low levels of pollutants can lead to a higher concentrations of pollution per breath we take. The indoor environment also has less air exchange than the air outdoors. In addition, the range of indoor environments and the wide variety of products we use indoors subject us to a much broader universe of pollutants. And finally, indoor environments often have elevated levels of humidity and dampness, conditions that exacerbate some pollutants, like biological organisms, which grow better in the presence of moisture.

Indoor air pollutants fall into several general classes: gasses (including environmental tobacco smoke), microbiologicals, pesticides, and particles.

Potentially harmful gasses

Microbiologicals

       These include bacteria, mold, mildew, viruses, animal dander, dust mites, and pollen from plants. (And not just house plants. Outdoor flora can contribute to the air that gets into our homes and buildings too.) Moisture and humidity help many of these biological agents proliferate indoors. Biologicals can grow inside the components of central ventilating systems, in carpets, walls, upholstery, and any location damaged by water. Biologicals cause infections and disease, allergic reactions, exacerbate asthma, and irritate the eyes and respiratory tract.

Pesticides

            These include insecticides, herbicides, miticides (used for lice) and disinfectants approved for household and indoor use. As with all indoor air pollutants, the levels of these individual pollutants are usually far below anything that could be harmful. But in the indoor environment, they contribute one more source to the mix of compounds in the air we breath. One study estimates that 80 percent of our exposure to pesticides occurs indoors.

Particles

            There are three unique categories of indoor particle pollution of the most concern.

            For the most part, indoor air pollution comes from indoor sources. But pollutants in outdoor air  (See Chapter 3, Air Pollution) can get indoors through windows, doors, and ventilating systems, and add to the mix of contaminants in indoor air

The Range of Consequences

The consequences of exposure to indoor air pollution are complex because of the wide range of pollutants, the diversity of indoor environments, and the varying susceptibilities of specific groups of people. While many of these consequences have not been studied enough to quantify them, even the partial estimates we do have suggest that indoor air pollution is one of the most serious environmental risks to public health.

The following chart describes common indoor air pollutants and their effects. Remember that the symptoms we describe below are often caused by a combination of pollutants rather than just one. Also remember that this area of public health is not well-understood. This is a general guide only. Finally, remember that individual sensitivities and widely varying pollution concentrations determine whether an individual suffers some, all, or none of these effects, and how severe the effects may be.

POLLUTANT

HEALTH EFFECTS

GASSES

Environmental “Secondhand” Tobacco Smoke

Immediate: Respiratory irritation, respiratory infection in children, decreased lung function, eye irritation.

Delayed: Lung cancer, heart disease, chronic respiratory problems

Radon

Immediate: None

Delayed: Lung Cancer (much higher rate in smokers)

Carbon Monoxide

Immediate: Low levels – nausea, fatigue, headache, chest pain in people with heart disease.

High levels – impaired vision, dizziness, confusion, seizures, brain damage, death.

Delayed: None

Nitrogen Dioxide

Immediate: Respiratory irritation, impaired lung function, increased respiratory infections in children.

Delayed: May contribute to onset of asthma

Organic Gasses

Immediate: Eye nose and respiratory irritation, headaches, nausea, Delayed: (at higher levels) damage to liver, kidneys, central nervous systems, possibly cancer.

MICROBIOLOGICALS

Bacteria, viruses

Immediate: Influenza and other airborne infectious diseases, infections, digestive problems.

Humidifier fever (described after the chart.)

Delayed: none

Molds, mildew, fungi

Immediate: Eye nose and respiratory irritation, skin rash, allergic reactions. Hypersensitivity pnuemonitis,

(described after the chart).

Delayed: none

Animal dander, dust mites, cockroach residue, pollen from indoor plants

Immediate: Allergic reactions

Delayed: might contribute to onset of asthma

PESTICIDES

Immediate: Eye nose and respiratory irritation.

Delayed: (at high levels) damage to central nervous system and kidneys, may increase risk of cancer.

PARTICLES

Asbestos

Immediate: none

Delayed: asbestosis, lung cancer

Particles

Immediate: Eye nose and respiratory irritation, increased respiratory infections, chest pain, heart arrythmias, heart attack.

Delayed: none

Lead

Immediate: none (except acute poisoning)

Delayed: Impaired mental functioning, especially in children, impaired hearing and motor control, decreased growth rate, behavior problems, impaired vitamin D metabolism, (higher levels) – kidney damage, anemia, severe brain damage, coma, death

In addition to these general health impacts, several specific diseases are linked to indoor air pollution. These include:

In addition to these specific diseases,  two widely publicized health

syndromes are also associated with indoor air pollution; sick building syndrome, and multiple chemical sensitivity. These are known as syndromes rather than specific diseases because they exhibit a wide range of sometimes vague symptoms and are triggered by a wide range of causes which have not been clearly identified.

Sick Building Syndrome (SBS)

            Symptoms of sick building syndrome include fatigue, difficulty concentrating, nausea, headache, eye nose and throat irritation, dry or itchy skin, and sensitivity to odors. There is sometimes no single set of symptoms, and no single identifiable source for those symptoms. Though SBS sufferers experience symptoms in direct relation to time spent in the building, the syndrome often affects people who occupy one part of the building more than others. SBS is far more common in office buildings and schools than in homes or other indoor environments. Symptoms usually abate after the person is out of the building for several hours or more. Most SBS episodes are eventually explained by exposure to certain materials, ventilation conditions, or a combination.

Multiple Chemical Sensitivity (MCS)

            This is a very controversial medical issue. Some people who suffer a wide range of illnesses affecting a number of bodily systems report that their illness is due to prolonged exposure to chemicals or other pollutants in indoor air. The syndrome is also sometimes called Environmental Illness, Chemical AIDS, and 20^th Century Disease.

But established medical associations such as the American Academy of Allergy, Asthma and Immunology say this condition does not exist. No clinical proof of this syndrome has been established and no widely-accepted definition even exists. One which is often citedwas written by the American Academy of Environmental Medicine, a group of health care providers known as clinical ecologists including allergists and physicians from other specialties, who treat people with this condition. They call MCS ”An ecologic illness that is a poly-symptomatic, multi-system, chronic disorder characterized by adverse reactions to environmental excitants, as they are modified by individual susceptibility in terms of specific adaptations. The excitants are present in air, water, drugs, and our habitats…”

            Theories suggest that sufferers, who are far more commonly women than men, may be experiencing dysfunction of the immune system or neurological abnormalities brought on after either severe chemical exposure (like a chemical spill) or after chronic low-dose exposures, including indoor air pollution. MCS patients say their symptoms are triggered by exposure to low levels of everyday chemicals such as those found in cosmetics, soaps, and newspaper inks. They report a range of symptoms that commonly includes headaches, rashes, asthma, depression, muscle and joint aches, fatigue, memory loss, and confusion. But nearly all the research on this issue indicates that these symptoms are too broad and the exposures that apparently cause them far too vague to support calling this an actual medical condition.

The Range of Exposures

Indoors means more than being at home or work. We’re also indoors when we shop, when we travel by car or bus or plane, when we go to the movies or the gym or the ice rink or the doctor or the hospital, and so on. Each of these types of indoor environment presents unique exposures. In some settings the issue is the sources of pollution – based on the materials used inside the building or vehicle, or the construction materials used to build it. Sometimes the most important determinant of exposure is the general nature of the building or vehicle–how it’s used, where it’s located, how it’s ventilated, and how it’s maintained. Many indoor environments have air quality exposure issues because of the susceptible populations that live in or visit those settings. We present this section in terms of the general types of indoor settings.

HOME

            Residential environments usually aren’t ventilated as well as offices, factories, or public buildings, especially in colder weather when homes are sealed more tightly to avoid air leaks in order to save energy and maintain comfortable temperatures. Humidity and moisture are a particular concern in residential buildings, generated by sources like kitchens, laundry rooms, bathrooms, and household humidifiers. Houses with below-ground basements are a uniquely residential source of indoor air moisture. Leaky roofs, walls and windows also contribute to the presence of biologicals in residential indoor air.

            In terms of the sources of pollution, radon exposure is greater in homes than other types of buildings. With the growing number of restrictions on smoking in public or workplace settings, ETS exposure is also more common in both houses and apartments. Organic gasses are emitted by some products most heavily used at home, such as pesticides, deodorants, cosmetics, household furniture, draperies, and stored fuels. Organic gasses can also come from household use of cleaners and disinfectants, paints and varnishes, adhesives, and carpeting. An EPA study found levels of these gasses in some homes could be as much as 10 times higher than outdoor levels, even when those homes were near a significant  outdoor source of such gasses, like petrochemical plants.

             Carpeting on foundation floors, where moisture from the ground dampens both the foundation and thus the carpeting, is principally a residential problem. Pet dander is too. Cockroach allergens are generally highest in residential buildings. Lead is principally a residential indoor air pollutant, caused by when lead paint in buildings painted before 1978 is released by abrasion with painted surfaces. This can be something as simple as raising and lowering a window, rubbing against a wall, or household renovation work.

Other respirable particles are generated indoors by cooking and heating appliances in addition to smoking. Particle pollution from outdoor sources can also become a problem inside homes near busy streets or highways. So can pollutant gasses that come from motor vehicle combustion like sulfur dioxide, nitrogen oxide, and carbon monoxide. These outdoor sources are abated if the home is air conditioned.

SCHOOL

The General Accounting Office estimates that half the schools in America have some sort of indoor air problem. Many schools suffer from poor ventilation. This is often due to efforts to save energy by minimizing the influx of outdoor air. Individual ventilation units designed to serve just one classroom are often simply turned off. Inadequate cleaning of filters, maintenance of ventilation equipment, or repair of leaks in roofs, walls, and windows is also a common problem for schools.

The general usage patterns of schools also contribute to unique indoor air pollution patterns. Schools are crowded buildings, permitted to have higher rates of occupancy than almost any other class of building. Since the young populations in schools regularly introduce biological pollutants – bacteria, viruses, and pet dander – crowding makes exposure worse. Also, children breathe more air per unit of body weight than adults, and more readily absorb contaminants into their still-growing bodies.  While this doesn’t make the air pollution in schools worse, it means that lower concentrations of contaminants may have more impact on children’s health.

Schools have a unique range of potential pollutants which include: markers, paint, adhesives and other art materials, science lab materials, vocational area materials, industrial cleaners and disinfectants, floor wax, and emissions from copying and printing machines. Asbestos is still found in schools because it was used as a fire retardant on boilers, pipes, in wall and ceiling tiles during construction, and in floor tile. Asbestos in schools was so common that in the mid-1980’s the federal government required that schools be tested for asbestos. Money was made available for abatement. These programs significantly reduced the problem nationwide. Radon can also be an air pollutant in schools which frequently have no basements, which means radon seeping into the building from underground immediately encounters occupied space.

WORK – OFFICE BUILDINGS

      The HVAC (heating, ventilation, and air conditioning) systems of many office buildings simply do not bring in enough fresh air. Sometimes this is the result of efforts to save energy and costs. Sometimes it’s because of poor maintenance of the ventilation system. HVAC systems, with their extensive networks of ducts and pipes, are often not cleaned. This includes failure to disinfect water supplies for cooling. Inadequate maintenance also means that sources of moisture in HVAC systems which can breed biologicals are not identified and repaired. Office buildings are frequently situated in environments where HVAC intakes recruit outdoor air contaminated from nearby sources of pollution such as areas with heavy traffic or dumpsters. Poorly designed office building HVAC systems sometimes locate their intake ducts too close to outflow vents, circulating some contaminants back into the building.

Office buildings sometimes contain spaces dedicated to special uses, like underground garages, restaurants, cleaners or printing shops. Potentially harmful emissions from these sources sometimes are carried in the HVAC systems of the overall building. Office buildings, with higher permissible occupancy rates than homes, are often converted buildings originally built for some other purpose. Ventilation systems are sometimes not adequately adjusted for the new, higher occupancy. Furnishings in office buildings, like moveable partitions, often interfere with designed airflows, reducing ventilation. Air ducts are sometimes simply blocked by filing cabinets, partitions, or other equipment or furniture.

In terms of unique sources of pollutants, asbestos is sometimes found in office buildings because it was used as a fire-retardant on boilers, pipes, and structural components. Industrial carpeting used in offices emits organic gasses. These gasses also come from printing and copying operations, and industrial cleaners and floor waxes. Biologicals come from inadequately cleaned and maintained HVAC systems, pipe, roof, or window leaks, and from water damaged walls, ceilings, or carpets.

WORK – INDUSTRIAL

There are a wide variety of industrial settings indoors, from factories to smelters to warehouses, really too numerous and varied to talk about in any detail. In general, levels of air pollution in indoor industrial environments are regulated by the Occupation Safety and Health Administration (OSHA). OSHA standards are usually more permissive than other environments, because the most vulnerable populations to air pollution – the young, the elderly, or those with compromised immune systems – are usually not the kinds of people who spend significant amounts of time in workplace settings.

Common indoor air pollutants in industrial settings include emissions from loading and hauling equipment like forklifts or from power equipment like generators, chemical emissions from manufacturing processes or raw materials, or dust or textile fibers.

HOSPITALS

      Hospitals have a number of unique challenges as Many people who spend time in hospitals are ill with infectious diseases. This means they are particularly susceptible to indoor air pollution, but it also means that the germs they carry are a source of that pollution too. In addition to the germs that people bring in, hospitals have unique sources of pollution compared with other buildings. Hospitals use much more chemically aggressive cleaners and detergents, and use them much more frequently, than in most other types of buildings. Disinfectants to clean and sterilize equipment include glutaraldehyde, formaldehyde, and volatile organics, which can be harmful at high levels. Topical antibiotics also contribute to indoor air quality issues in hospitals. The dust from latex gloves used by medical providers has been shown to cause allergies. Hospitals also use a large number of individually wrapped disposable items, and the cellulose fibers from these packages contributes to particle pollution in the air.

Hospitals also have unique challenges to ventilation systems, which have to be much more advanced than in most other buildings. Hospital ventilation systems have to segregate air flows from various parts of the building. They have to filter the air much more aggressively. And in many locations like operating rooms and intensive care units they have to maintain air pressure in such a way that the air flows into the room and up into the ventilation system, not out of the room and into the general building. This heavy reliance on aggressive mechanical ventilation systems means that any failure can have serious consequences for indoor air quality.

TRANSPORTATION

      Millions of people spend several hours each week in their cars, vans, or trucks. They are indoors, but the air they’re breathing contains many outdoor air pollutants brought in by the vehicle’s circulation system. One study found that in Boston, levels of two outdoor air pollutants known or suspected to be carcinogens were higher for people in their cars driving to work than they were for people walking or riding their bikes. Any leaks in your vehicles exhaust system or problems with your emissions control equipment can expose you to elevated levels of carbon monoxide, nitrogen oxide, particles, and organic gasses that are supposed to be going out the tailpipe. Biologicals are emitted from vehicle cooling and heating systems. That “new car smell”  is actually organic gasses from plastic components inside the car. And don’t forget that the volume of air inside a motor vehicle is pretty small, so concentrations of pollutants, including carbon dioxide, can build up quickly.

      Studies have found that levels of many typical urban air pollutants are lower in mass transit vehicles than they are in cars. This is possibly because of larger volumes of air, on these vehicles and because their doors are opening all the time, increasing ventilation.

      Have you ever gotten a cold or some other infectious illness after an airplane trip? The close proximity of airplane passengers for extended periods is just one unique form of indoor air quality issue on planes. Concentrations of some chemicals, and particles, can rise dramatically while the plane is on the ground. A mix of sources exists on planes, where tests have found chemicals associated with cleaners, cosmetics, air fresheners, dry cleaning fluid, and jet fuel.  Carbon dioxide levels on commercial planes can reach levels that indicate inadequate fresh air ventilation.

RECREATION

      One type of recreational building has a particular indoor air problem; small local ice rinks.  The problem is caused when ice cleaning machinery, most commonly known by the trade name Zamboni, drives around hourly, as many as 14-15 times each day, emitting carbon monoxide and nitrogen dioxide, often at high levels if the ice cleaning machine isn’t equipped with pollution control equipment. These gasses build up because many of these rinks do not ventilate, often because outside air is either too warm, requiring more cost to keep the ice surface refrigerated, or too cold, requiring rink managers to heat the seating and observation areas. Concentrations are greatest near the ice where skaters are exerting themselves and breathing heavily, since the cold tends to make the air in the rink sink and the boards around the rink contain the pollutants. Both conditions make it harder for ventilation systems to remove contaminants.

      “Hockey headache” and “skater’s cough” are common complaints among skaters, describing the effects of carbon monoxide and nitrogen dioxide exposure. Many rinks are solving the problem by putting pollution control equipment on their ice cleaning machinery, by purchasing pollution-free electric-powered machinery, and by ventilating their rinks more often.

This problem does not affect large professional ice hockey arenas, because the volume of air inside is greater, because such arenas are ventilated, and because the ice cleaning machinery is properly equipped and only operates three or four times a day.

One other type of indoor recreational activity may not seem like it’s indoors at all. But when you are camping and inside a tent, you are in an enclosed ‘indoor’ environment where pollutants can build up, especially if the tent is not vented. Propane heaters and stoves can quickly produce dangerous levels of carbon monoxide. These should not be used in a tent at all.

Reducing Your Risk

With all of the various sources of pollution, and all of the different kinds of indoor environments, an entire book could be devoted to detailing the specific steps you can take to reduce the risk from poor indoor air quality. But regardless of the specifics, some general steps are often helpful. (These are the same steps that you should request for indoor environments you don’t control.)

First, eliminate the sources of contamination.

Second, ventilate. Even if the outdoor air is polluted, concentrations are probably not as high as they are inside. An EPA study found that concentrations of a dozen common organic gasses in homes were 2-5 times higher indoors than outdoors, whether the home was in the city, suburb, or country.

Finally, air cleaners and filters are helpful, but without these other steps they won’t solve the problem. Neither will house plants.