Pollution from power plants, cars, and other transportation is a well-known contributor to outdoor air pollution, but our indoor air quality is often worse; it can be up to 10 times worse for you than the air outside. Microbial pollutants like mold, pet dander and plant pollen can combine with chemicals like radon and volatile organic compounds (VOCs) to create a pretty toxic environment in your home; since we spend an average of 90% of our time indoors and 65% of our time inside our homes, according to the National Safety Council, that can add up to allergies, asthma and worse.

Everything that comes in to our homes has the potential to be harmful to our health; this includes things from the building materials and elements that hold our homes together to the furniture we sit on and the paint that goes on the walls. Indoor air pollution can be bad, but it doesn't have to be.But first, what causes poor indoor air quality? Read on to find out…

What causes poor indoor air quality?
Indoor air pollution can be easy to manage once you understand where it comes from. Looking at the image above gives you some idea of the more common sources for poor indoor air quality. In many cases, it comes from chemicals that are part of the things that you bring into your home; the polyurethane common in mattresses, formaldehyde and organic chemicals like dioxin, polychlorinated biphenyl (PCB) and polybrominated biphenyl (PBB)used in lots of furniture and other interior elements are all harmful to us humans. Drapes, carpets and other absorbent fabrics can help trap these nasties, along with dust, mites and other allergens, and our modern, mostly airtight homes keep them inside. Remember this: if there are chemicals and VOCs in a product, there are chemicals and VOCs that could come out, and they won't be good for you if they do.

More causes for indoor air pollution

Not having proper ventilation can also help promote mold and other microbial growth, especially in damp climates; if cellulosic materials (like paper, wood and drywall) become moist and fail to dry within 48 hours, mold colonies can propagate and release allergenic spores into the air. As such, a basic way of maintaining the health of indoor air is by the frequency of effective replacement of the indoor air with cleaner outdoor air.

However, knowing the causes of poor indoor air quality is only half the battle. Read on to learn how to test for poor indoor air quality.

Testing for poor indoor air quality

Aside from keeping known pollutants out of our homes, there are several strategies for keeping the indoor air healthy. At the top of the list is maintaining proper ventilation, which can be done most easily by just opening up the windows at regular intervals (even in the winter). Using green cleaning products can help cut way back on the toxins in your home, as citrus and pine-based solvents can react with ozone to create formaldehyde. Keeping pesticides out of your garden and off your lawn can also help, as they're easy to track in on shoes and clothing. It's also important to keep filters and vents clean, as pollutants can cycle through air ducts and central heating and cooling mechanisms.

Avoiding poor indoor air quality: 

Check out our top 5 plants for improving indoor air quality, our picks for improving the quality of the air in your homes, and read up on considerations when picking out an indoor air filter. For outside sources, we recommend checking out the US EPA's indoor air quality site, along with the US National Library of Medicine's Environmental Health and Toxicology indoor air quality section and the Medline Plus Indoor Air Pollution section.

Improving Your Home’s Indoor Air Quality: From Basic to Bigger and Better Steps

By Willem Maas

According to the Environmental Protection Agency, indoor air is often more than 10 times (and sometimes more than 100 times) more polluted than outdoor air. Indoor air pollutants contribute to asthma as well as other respiratory conditions and diseases. Indoor pollutants include VOCs (volatile organic compounds) from offgassing building materials, paints and finishes, and furnishings; other toxic chemicals emitted from cleaning products, pesticides, and hazardous household supplies; mold, which grows on moist materials and surfaces; carbon monoxide and nitrogen dioxide gases, which can be released from gas-fueled combustion appliances; particulates from wood-burning fireplaces or cars running near the house; tobacco smoke; as well as asbestos, lead, and radon.

Indoor air quality (IAQ) can be particularly compromised during winter and summer months when the home is more likely to be sealed tight to keep heated or cooled air from escaping.

The three general strategies for improving IAQ are:

•  source control
•  improved ventilation, and
•    air cleaning

Source control—eliminating sources of pollution or reducing their emissions—is the most effective and should be the first step you take. Many source control options are easy and inexpensive.

Improved ventilation will improve indoor air quality by increasing the amount of outdoor air coming into your home, diluting concentrations of indoor pollutants, and pushing stale indoor air out of the home. However, some ventilation improvements may increase energy costs unless you make design changes to your home. The third strategy, using mechanical air cleaners to filter pollutants out of your indoor air, can be used to supplement source control and ventilation but it is not recommended as the sole solution.

Below is a range of tips—from basic to better to best practices—for protecting and improving the air quality in your home.  For additional information about indoor air quality and healthy homes, visit the EPA’s Indoor Air Quality website or the American Lung Association’s Health House website.

Basic Steps to Cleaner Air

These easy and inexpensive source control measures will eliminate pollution or reduce emissions from cleaning products, gas appliances, building materials, and furniture.

Clean with the least toxic product that will do the job.

The powerful chemicals in many conventional cleaning products can have a toxic effect on human skin and lungs. In addition, the propellants in aerosol products can be inhaled, so it’s prudent to use pump products instead. Find out how to make nontoxic cleaners from common household ingredients (such as vinegar and baking soda)here. Or you can purchase nontoxic or less-toxic formulated cleaning products at most stores. GreenSeal, Greenguard, and Scientific Certification Systems(SCS) certify residential cleaning products that comply with their green standards.

Avoid having your clothing conventionally dry-cleaned, or air out dry-cleaned clothing before bringing it inside.

Perchloroethylene (PERC), the most commonly used dry-cleaning solvent, is a potential carcinogen. In a report titled Hung Out To Dry, the Coalition for Clean Air recommends allowing cleaning solvents to offgas by removing clothes from the plastic dry-cleaning bag and placing them outside for four to five days. Alternatively, most fabrics that are labeled “dry clean only” can actually be cleaned through a PERC-free “wet cleaning” process that is increasingly being offered by professional dry-cleaning shops, or some can even be cleaned at home using a mild soap. For more information on alternatives to toxic dry cleaning, read these articles from Green America and Consumer Reports’ GreenerChoices.

Dispose of unused paint, solvents, pesticides, and other household chemicals promptly, and tightly close the containers of products still in use.

These products can emit harmful gases that pollute the air and may cause health problems. Minimize the use of hazardous products as much as possible. For essential household chemicals, buy them in smaller sizes that you can use right away. Earth 911 offers an easy-to-use national directory of safe disposal sites for toxic household wastes. If you need to store any hazardous chemicals, keep them in a ventilated and locked outdoor shed away from children, pets, and flame sources.

In temperate climates, use natural ventilation to cool your home.

A natural ventilation strategy relies on the buoyancy of hot air (the stack effect) and wind (cross ventilation) to increase the amount of outdoor air coming into your home. Natural ventilation can reduce total energy consumed by 10 to 30 percent compared with a home using a forced-air cooling system.

While natural ventilation is best incorporated into a home’s overall design (e.g., proper window placement when designing the home), there are simple ways to apply natural ventilation in any home: open both the top and bottom sashes of double-hung windows, and open windows on opposite sides of the same room for cross-ventilation. Opening windows at night during the summer will bring cool, fresh air inside and the thermal mass of the house will help the interior stay cool for part of the next day. The greater difference in temperature between inside and outside air at night also will cause more rapid air exchanges and vent air pollution from inside more thoroughly. In addition, outside air may be cleaner at night due to fewer cars on the road.

Use the exhaust fan over your stove to remove gases like carbon monoxide and nitrogen dioxide, and fans in your bathrooms to remove water vapor.

Make sure your gas range has a hood fan that exhausts to the outside—some exhaust systems are ductless hoods that exhaust air pulled from the stove right back into the home. Bathroom fans are also important since poor moisture management in a home can allow molds to grow. Also, if your home’s walls, doors, and windows are tightly sealed and energy efficient, you may need to open a window slightly when running an exhaust fan or when you’re using a fireplace, to avoid creating negative pressure. Without another way for outside air to replace the air leaving through the exhaust fan or chimney, air may be drawn through the exhaust pipes for your furnace or hot water heater.

Employ other simple moisture management measures to keep your home’s interior dry.

Be sure to fix any leaks and clean up any household spills as quickly as possible. Standing water and moist materials provide a habitat for mold and microbial growth (and can also attract pests).

Replace the air filter in your furnace and air conditioner at the start of the heating or cooling season, or as recommended by the manufacturer.

Filters actually become more effective in capturing and removing particulate air contaminants as they get dirtier and build up a “dust cake.” This increased effectiveness comes with a cost, however, as the pressure drop increases and less air gets through. It is a good idea to change the filter for the furnace at the start of the heating season, as the dust cake from the previous year has been sitting in the cold, dark basement throughout the summer and may have started to grow molds.

Room-size air cleaners can be effective tools for removing pollutants in one or more rooms.

If you are concerned about pollution in a particular room and it’s not possible to remove the pollution source, consider buying a room-size air cleaner. Sources like Consumer Reports and the American Lung Association recommend air cleaners for improving air quality in one or several rooms, but not for the whole house. See the EPA’s Guide To Air Cleaners in the Home for information on the various types of air cleaners.

Don’t allow smoking inside your home or around your home (near your windows or doors).

This one may seem obvious, but lest anyone forget, tobacco smoke is a pollutant.

Better Steps to Cleaner Air

These steps to improved indoor air quality are modestly priced but may require some advance planning.

Remodel in temperate months of the year, when you can open outside doors and windows to naturally ventilate construction areas without reducing energy efficiency.

During the winter and summer months when heating or cooling systems are in use, opening doors and windows will reduce your home’s energy efficiency. So if you’re doing any remodeling or home improvements that involve noxious fumes (e.g., painting, gluing, sealing), it’s best to do the work when the weather is mild and you can have doors and windows open. Direct floor fans towards the open windows to exhaust the fumes outdoors. Also, when applying emitting finishes, such as paint, remove absorptive items (such as upholstered furniture and rugs) from the room so that they don’t absorb and re-release the VOCs.

Use low-emitting, low-maintenance building materials to achieve improved indoor air quality year round.

Selecting low-VOC (low in volatile organic compounds), low-emitting, low-maintenance products can help you reduce the amount of pollution released into your home’s indoor air, thereby avoiding the need to take more drastic steps to clean dirty air. See GreenHomeGuide’s Know-How series for advice on selecting healthy flooring, furniture, paints and coatings, and insulation (formaldehyde-free). Also look for low-VOC adhesives and caulk, and pressed wood products (e.g., particleboard) that do not contain urea-formaldehyde. Greenguard, GreenSeal, and the Carpet and Rug Institute (Green Label Plus) certify building products that meet IAQ criteria.

Reduce the use of carpeting, and keep carpeting clean and dry.

Carpeting can absorb water and trap particulates and other contaminants; some types of carpeting also contain high levels of VOCs. Where possible, select a non-absorptive type of flooring. Never use carpeting in the kitchen, bathroom, laundry room, basement or other areas of the house that are regularly exposed to moisture. Areas that are carpeted should be vacuumed regularly, ideally with a HEPA (High Efficiency Particulate Air filtering) vacuum. And if carpeting gets wet, make sure that it is completely dried within 12 hours to prevent mold growth. When having carpeting professionally cleaned, you can choose a company that uses a no-chemical and low-water process.

Add a fresh air intake to your forced-air heating/cooling system’s ducting.

A fresh air intake will allow fresh replacement air to enter the house when you’re using exhaust fans or the fireplace. If you already have a ducted air system, you can add a dedicated outdoor air opening by extending the return-air ductwork to the outside. To ensure fresh air delivery, use a system with automated circulation (e.g., a fan-cycler). You may also want to install a filter in this outdoor air source to capture air contaminants such as pollen and prevent them from entering your house. 

Install a whole house fan system.

A “whole house” fan system brings stale indoor air upwards and out the top of the house through the attic vents. This type of fan system also provides a good, energy-efficient alternative to air conditioning on moderately warm days. (Note: If you live in a particularly humid climate, also consider using a dehumidifier.)

Design your garage to keep vehicle fumes from entering your home.

If you’re building a new home, consider building a detached garage (or no garage). If you have an attached garage, tightly seal the wall between the garage and your conditioned space, and install an exhaust fan system that either runs continuously or uses an automatic timer linked to an occupancy sensor, garage door opener, or carbon monoxide detector. Also, do not install HVAC equipment or air-handling ductwork in the garage.

Bigger Steps to Cleaner Air

Even if you take all of the steps above, your home could still contain sources of indoor air pollution. The following are some additional technologies and strategies that may be more complex or costly to implement, but they can provide substantial improvements in indoor air quality.

Install an energy recovery ventilator (ERV) to provide a continuous supply of fresh air while minimizing loss of heat and water vapor.

This ventilation system (also referred to as an air-to-air heat exchanger) is connected to the existing forced-air heating/cooling system and uses fans to exchange stale indoor air with fresh outdoor air. Note that these systems cost several thousand dollars, so they do not have an immediate payback. This article from the University of Minnesota answers common questions about ERVs. To make sure that the incoming air is adequately filtered, select a system that has a HEPA (High Efficiency Particulate Air) filter, or a filter with a high MERV (Minimum Efficiency Reporting Value), i.e., a minimum MERV of 8 or, even better, 10 or higher.

Use a heat pump water heater to increase energy efficiency and improve indoor air quality.

Heat pumps achieve energy efficiency by moving heat around as opposed to liberating it—the heat for the next batch of water to be heated is reclaimed from the warm, humid air being exhausted. Heat energy comes both from cooling the air being exhausted from about 72° F to 42° F (sensible heat reclamation) and from the condensation of the water vapor back into a liquid (latent heat reclamation). Heat pump water heaters use 30 to 50 percent of the electricity consumed by conventional electric water heaters.

The improved IAQ stems from the moisture management aspect of this approach. The amount of mechanical ventilation provided directly matches the amount of hot water consumed. Also, because the hot water use reflects the level of human occupancy (with more people in the home, more washing occurs), the result is mechanical ventilation with heat recovery that corresponds to occupancy levels. Note: Some experts have expressed concerns about the reliability of heat pump water heater systems. For guidance on how to select the right system and have it properly installed, read this article from the Department of Energy.

Install a radiant hydronic heating system rather than a forced air system.

Forced air systems stir up dust and allergens because they heat a home by blowing heated air into it. Radiant hydronic systems heat a space by pushing warm water through tubes underneath the floor; the warm floors radiate heat, rather than pushing air and dust around. It is easiest to install a radiant heating system when building a new home or an addition, but they can also be added to existing rooms.

Toxins Hiding in Our Homes Look Like this:

Phthalates

Phthalates are man-made chemicals commonly used in various types of plastics, including flexible kids' toys, but they can also be found in a wide range of products like cosmetics and vinyl flooring. Though researchers have yet to determine what levels of exposure might be harmful to humans, animal studies have shown that phthalates disrupt hormones and cause birth defects in male genitalia in animals. The European Union has already banned different types of phthalates from cosmetics and toys. As an alternative to products with phthalates, try wood toys or phthalate-free cosmetics.

Bisphenol A

Bisphenol A is a chemical that mimics estrogen and is often used in hard plastic items like Nalgene bottles, water pitcher filters and baby bottles. Bisphenol A has been linked in animals to infertility, enlarged prostate, abnormal chromosomes, obesity and insulin resistance, a precursor to diabetes. Like with phthalates and flame retardants, researchers are still trying to determine what levels of bisphenol A are dangerous to humans. To be extra careful, try using products without bisphenol A like stainless steel water bottles.

Household Cleaners

The products under your kitchen sink may contain harmful toxins, according to the Environmental Protection Agency. This includes counter-top and oven cleaners, window and insect sprays and furniture polish. Among the ingredients frequently used in household cleaners are ammonia, lye, phosphate, pesticides and chlorine. These substances can cause eye, nose, ear, throat and skin irritation and can sometimes be fatal if swallowed. When using cleaners with dangerous substances, be sure to wear rubber gloves to protect the skin, enable sufficient air circulation by opening a window or running a fan and never mix two cleaners of different kinds together, particularly if they combine ammonia and chlorine–together they produce cloramine gas, which can be fatal when breathed. Also explore natural alternatives like vinegar or products that don't use toxic chemicals.

Mold

According to the Centers for Disease Control, mold itself is not toxic, but it can produce toxins that cause uncomfortable physical reactions like upper respiratory difficulty, wheezing or skin irritation. Mold grows in poorly ventilated, moist areas and in materials like wood, drywall, carpet and upholstery. Colleen Mathews, a specialist in indoor air quality for the Environmental Protection Agency, says that reactions to mold should dissipate upon leaving an affected area. If you suspect mold is responsible for an adverse physical reaction, examine your home's ventilation system, particularly in the bathroom and north-facing rooms, which often experience high levels of moisture.

Carbon Monoxide

Unfortunately, there are no physical signs of carbon monoxide poisoning until it turns fatal. The Centers for Disease Control advises people to install a battery-operated carbon monoxide detector in their homes. Also, be sure to have a technician service the heating system, water heater and any other gas, oil or coal-burning appliances each year. Avoid running a car or truck inside a garage even if the door is open and don't use a generator, charcoal grill or other gasoline or charcoal-burning devices inside your home, basement or garage.

Flame Retardants

Polybrominated diphenylethers, or PBDEs, are a certain class of flame retardant chemicals, which are designed to slow a fire and provide adequate time for escape. They are included in household items from consumer electronics to upholstery to wire insulation to furniture foam. Though researchers have yet to determine what level of exposure in humans might cause negative health effects, animal studies have shown that high levels of exposure interferes with thyroid hormone, which is essential for healthy brain development. In order to find out what types of flame retardants are in your household, try contacting the manufacturers of items like couches, television sets and small appliances.

Environmental Tobacco Smoke

Smoking in your home is a big no-no. Breathing second-hand smoke may cause infants and children to develop asthma, upper respiratory infections or persistent pneumonia and bronchitis. In adults, it can cause a number of ailments, including headaches, wheezing and nasal congestion. The Environmental Protection Agency recommends eliminating smoking from the home completely as opposed to just improving ventilation.

Formaldehyde

The Environmental Protection Agency has classified formaldehyde as a probable human carcinogen. It's commonly found in plywood, particleboard, paneling and fiberboard as well as in furniture, cabinets and certain types of fabric and draperies. Physical symptoms, which can change depending upon the length and the level of the exposure, include upper respiratory irritation and burning or tingling in the eyes, nose and throat. The EPA estimates that 10% to 20% of the U.S. population may have "hyper-reactive" airways, making them more prone to experience formaldehyde's effects.

Radon

Radon gas is odorless, tasteless and invisible but also deadly: It can cause lung cancer at high enough exposure levels. According to the Environmental Protection Agency, an estimated 21,000 people die of radon-linked lung cancer deaths per year. A natural but radioactive decomposition of uranium in the bedrock releases radon into the air. It can seep into your house through the basement and cracks in walls and floors as well as other gaps in construction. Testing for radon exposure is easy, however, and can be done with store-bought kits or by a qualified tester. Check with your state radon office for a list of qualified testers.

How about improving your indoor air with indoor plants!

Boston Fern has the highest rating for removing the toxic gas formaldehyde by houseplants according to the "How to Grow Fresh Air" book.

Areca Palm rated highest for xylene and toluene removal.