Invisible Home Dangers

By Rebecca Morley, Executive Director, National Center for Healthy Housing

Invisible Home Dangers

Numerous studies, dating back to the industrial revolution and beyond, have recognized the association between health and housing. Tenements, designed to solve the housing crisis of the 19th century, were found to be breeding pools for contagious diseases. Tenement architecture, which favored narrow design, cheap building materials, and little to no ventilation or natural light, led to overcrowded and unsanitary conditions and was linked to the emergence and spread of infectious diseases including cholera, tuberculosis and typhoid fever.

In recent years, health issues related to the building design and development as well as to the materials used in construction have taken center stage. Lead-based paint hazards cause severe developmental issues and brain damage, especially in children. Asbestos is highly carcinogenic. And early efforts to improve building performance may have contributed to “sick” buildings, in which high levels of indoor air pollutants were found.

Indoor pollution levels range from 2 to 5 times higher (and in some instances 100 times higher) than outdoor pollutant levels and may pose greater health risks to individuals. People spend approximately 90% of their time indoors. Poor air quality increases the incidence of asthma and other respiratory diseases, making individuals that spend the greatest amount of time indoors, such as children, seniors and the chronically ill, the most susceptible to indoor pollutants and these ailments.  

A 1984 report by the World Health Organization (WHO) found that up to 30 % of new and remodeled buildings had excessive indoor air quality problems due to:

  • Inadequate ventilation: Conservation measures sparked by the 1970s energy crisis called for a reduction in ventilation from outdoor air sources. Although ventilation standards were later revised, inadequate ventilation remains an issue in many buildings as existing standards were largely designed to address comfort, not indoor contaminants.
  • Indoor chemical contaminants: Indoor air pollution is caused by sources within the building itself, as well as by the occupants. Volatile organic compounds (VOCs) such as formaldehyde may be released from building materials and cleaning products. Tobacco smoke creates high VOC levels, as well as other toxic compounds, such as particulate matter. Unvented or poorly vented appliances, fireplaces, kerosene and gas space heaters, and woodstoves can create combustion byproducts such as carbon monoxide, nitrogen dioxide, and particulate matter.
  • Outdoor chemical contaminants: Sometimes, even outdoor air that enters a building contributes to indoor air pollution. Poorly located intake vents, windows and doors may allow pollutants such as motor vehicle exhaust to enter buildings; improperly placed plumbing vents and building exhausts (e.g., bathroom and kitchens) can create a “short circuit,” permitting pollutants that were intended to vent outside the building to re-enter. Cancer-causing radon gas can seep into homes through cracks or holes in the foundation. Pesticides and other outdoor contaminants can be tracked into the house on clothing and shoes.
  • Biological contaminants: Biological contaminants include bacteria, mold (fungi), pollen and viruses. Excess moisture may increase the level of these contaminants. Stagnant or accumulated water can be found in ducts, humidifiers and drain pans, or leak into ceiling tiles, carpeting, insulation or even drywall. Insect droppings are additional sources of biological contaminants.

These contaminants are often mixed, creating a toxic soup of indoor exposures that add to other issues creating occupant discomfort such as inadequate temperature control, humidity, or lighting.

Three of the most hidden home hazards include: radon gas, carbon monoxide, and lead-based paint. These hazards are invisible to the naked eye. You can’t smell, see, or taste them and as a result, most people ignore them until it’s too late.

Most everyone knows that the sun gives off natural radiation. The earth gives off natural radiation too, which can seep into your home and become an indoor air hazard for your family. This form of radiation is called radon gas and it comes from the natural breakdown of uranium in rocks and soil.

Radon is invisible and odorless and can appear in any type of home: old, new, with or without a basement. Radon is the second leading cause of lung cancer among smokers and the top cause of lung cancer among non-smokers. It is responsible for about 21,000 lung cancer deaths each year — killing more people than even drunk driving.  

High indoor radon levels have been found in every state. The U.S. Environmental Protection Agency (EPA) estimates about 1 in 15 homes have high levels of radon. That’s about 8 million homes with high levels.

Radon is consistently rated as one of the top environmental risks addressed by the federal government and the leading environmental cause of cancer. Testing is the only way to know if your home has elevated radon levels. Do-it-yourself test kits are available online and at retail outlets or by calling your state radon office. You can find out more about testing for, and fixing home radon problems at

To learn more about unsafe levels, home testing and reducing your exposure to radon, click here.

Carbon Monoxide
Carbon monoxide (CO) is known as “the silent killer.” You cannot see it, smell it or taste it. CO claims the lives of nearly 300 people in their homes each year according to the U.S. Consumer Product Safety Commission (CPSC). CO is a deadly gas that is produced by fuel-burning heating equipment, such as furnaces, wood stoves, fireplaces and kerosene heaters.

Carbon monoxide (CO) is a deadly gas that is difficult to detect because it is odorless and invisible. As a result, it is known as “the silent killer.” According to the U.S. Consumer Product Safety Commission (CPSC), this poisonous gas kills nearly 300 people in their homes each year.

CO is produced by fuel-burning appliances and equipment in our homes. If you have heating, cooking or power equipment that uses fuels such as oil, natural gas, coal, wood, propane, gasoline, etc., then your home is at risk for potential CO poisoning. Homes with attached garages are also at risk, because vehicles left running in the garage can cause CO to seep into the home.

Symptoms of CO poisoning are similar to symptoms of the flu, and can include headache, dizziness, nausea and shortness of breath. To distinguish between symptoms of flu and CO poisoning, if you feel better after leaving home and then worse again when you return, it may be CO exposure causing the symptoms.

CO poisoning can be prevented by proper care and use of household equipment.

  • Have a trained professional inspect, clean and tune-up your home’s central heating system and repair leaks or other problems. Fireplaces and woodstoves should also be inspected each year and cleaned or repaired as needed.
  • Never use an oven or range to heat your home.
  • Never use a gas or charcoal grill inside your home or in a closed garage.
  • Portable electric generators must be used outside only. Never use them indoors, in a garage or in any confined area that can allow CO to collect. Follow usage directions closely.
  • Install at least one CO alarm near sleeping areas and ideally, on each floor of your home.

If your CO alarm sounds, check to see if it is plugged in properly, or if battery-powered, check the battery to be sure the device is operating. If you suspect that CO is leaking in your home, follow these steps:

  • Call to report that you suspect CO is accumulating. Usually the appropriate agency to call is the fire department or 9-1-1. They may recommend that you open all windows or evacuate the home. If you are experiencing symptoms such as a headache, stomach ache or dizziness, evacuate the home.  
  • Seek immediate medical treatment for anyone who has severe symptoms.
  • Follow the advice of the responding agency before re-entering your home, and quickly obtain repairs as needed.  

For more information call the Consumer Product Safety Commission (1-800-638-2772) or visit

Lead-Based Paint
Although many people believe that lead poisoning was a problem of the past, about 240,000 children are impacted by it each year. That’s because lead-paint remains in nearly 38 million homes in the U.S. Most homes built before 1978 contain some lead paint. Lead-based paint may be a hazard if it is:

  • Flaking, peeling or chipping;
  • On a friction or impact surface (i.e. windows, doors, floors);
  • On a child-accessible, chewable surface (i.e. a windowsill).

Lead can also become a hazard if it is disturbed through remodeling or renovation activities such as dry scraping, sanding, pressure blasting or burning. In fact, each year, more than 1.4 million children are at risk of lead poisoning when their older homes are renovated.  

Children under age 6 are at greatest risk because their nervous systems are still developing and lead can interfere with the brain’s development. Because young children are exploring their environments, they are at greater risk than adults. Most children are poisoned by invisible lead dust that settles on floors and other surfaces where it can easily get on children’s hands or toys and into their mouths. Lead exposure can affect how quickly children learn and advance in school and it may even affect growth and hearing. You cannot tell if a child is lead poisoned just by looking. If you suspect your child has been lead poisoned, take him or her to the doctor’s office and request a simple blood test.

You can hire a certified professional to test your home and tell you where lead-based paint and lead dust and soil are located in and around your home. Also, you can hire a certified firm to remediate lead-based paint hazards.

Before hiring a contractor for renovation work or home repairs, check the professional’s credentials to make sure that they are an EPA certified lead renovator. Workers should not spread lead dust and the work space should be sealed off before work begins and the paint should be wet before it is sanded or scraped to control the spread of lead dust. Workers should thoroughly clean up and test for lead dust before they complete the job.

For more information:

Call the National Lead Information Center (1-800-424-Lead or visit

Call the National Center for Healthy Housing (1.877.312.3046 or visit

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