Friday, December 29, 2006

Home Renovation and Asthma Attacks

I am renovating my home. Dust is everywhere and my daughter has had several asthma attacks as a result. We have since moved to my parent's house. How will I know when it is safe to move back home?

Since the dust generated during your renovation is primarily made up of large particles that settle quickly onto surfaces, it is likely that dust levels inside your home will quickly settle back to normal as soon as your home renovation is over. However, there will probably be a lot of dust on your floors, walls, and other inside surfaces. This deposited dust can be resuspended (or lifted back) into the air when you move around your home or with the air drafts.

Before you move back home, I would clean all surfaces in your home, including floors, walls, furniture, and vents, to make sure that they are free of dust. I would clean non-carpeted surfaces using a wet wash cloth (or mop) with soap and carpeted surfaces using a vacuum cleaner with HEPA bags. The HEPA bags will make sure that any dust picked up by your vacuum cleaner stays in your vacuum cleaner. [I think that HEPA bags can be used in most vacuum cleaners, but am not sure.]

As an extra precaution, you could measure indoor particle levels and check whether they are back down to normal levels. Without (and sometimes even with) connections, this is not so easy to do, as portable, easy-to-use and reliable particle measurement devices are difficult to find and are quite expensive. Particle measurement devices are used primarily by people in research or the government; as a result, they are not made for the mass market. A possible option would be to ask an environmental consulting firm to make the measurements for you. I think that this option is probably not worth it (unless your problem is big), as it would be very expensive and your request may be too small for them to take the job. A second option may be to borrow equipment -- with some guidance and instructions -- and make the measurements yourself. You will need some connections to make this second option a true possibility. I may (with the emphasis on may) be able to help in this regard. If you are interested, drop me a note and I will see what I can do.

Sunday, December 24, 2006

Portable Air Cleaners: Things to Consider

What portable indoor air cleaner should I buy to remove air pollution from inside my home? I want to use the air cleaners to reduce my wife’s suffering from multiple chemical sensitivity.

If your wife spends most of her time at home in one or two rooms, then placing a suitable portable air cleaner near her in each room should help reduce particle levels - and thus improve your indoor air quality. If she spends time at home in many rooms or your home has an open floor plan, portable air cleaners may not be the best solution. You may want to look at other possible solutions, such as a whole house air cleaning system. You should be aware that air cleaners generally don't remove everything -- most don't remove bad smells or get rid of all potentially harmful gases from the air – be suspicious of such claims.

Portable air cleaners are the most common type of air cleaner. They are small and plug into the wall much like a counter-top kitchen appliance or a portable heater. There are many brands and models of portable air cleaners to chose from. In choosing the best portable air cleaner for you, you should consider the following three factors:

Efficiency. Most portable air cleaners use a filter to remove dust and other particles from air that is moved through the filter by a fan. The efficiency of the filter is the fraction of particles removed by the filter. The best performing portable air cleaners have HEPA-grade efficiency, meaning that they remove at least 99.97% of 0.3 micron particles from the air that passes through them.

Clean Air Delivery Rate. The performance of portable air cleaners is typically determined by its “Clean Air Delivery Rate” or CADR. Conceptually, CADR is the amount of clean air delivered each minute by the air cleaner. In practice, CADR can be calculated from the airflow rate of the fan and the filter efficiency. For example, a portable air cleaner with a flow rate of 200 cubic feet per minute (cfm) and a 50% efficient filter would have a CADR of 100 cfm. CADRs can usually be found on the box of the air cleaner. [The Association of Home Appliance Manufacturers (AHAM) provides more detailed explanation of air cleaners and lists model-specific CADRs at] Notably, portable air cleaners without fans, such as many ionic type models, do not have a CADR rating because they do not have a fan to deliver air through the filter. As a result, models without fans are generally ineffective (e.g., are a waste of money) because they don't clean enough air to make a difference in your air quality.

Room Size. Portable air cleaners work best inside an enclosed space, for example a bedroom with closed doors and windows. The best air cleaner for your home will have a CADR equal to the square footage of the room that you want to clean. An air cleaner with a substantially larger CADR may be too noisy and create too many drafts. On the other hand, an air cleaner with CADR much smaller than the area of your room will not clean the air fast enough for your room size. In this case, you could purchase several portable air cleaners which together have a large enough CADR to clean the same large room. This solution may be sufficient for your needs, although testing has shown this solution to be relatively inefficient.

On a more personal note, I would stay away from ionic or electronic air cleaners that produce measureable amounts of ozone , a pollutant that has been shown to be harmful to health. Look for test results from companies making ionic or electronic air cleaners to make sure that the air cleaner does not produce measureable amounts of ozone (say over a couple parts per billion or ppb) in your living space. Some ionic or electronic air cleaners will include a scrubber to remove the ozone. I would still be wary of these air cleaners, as it is possible that faulty operation, installation, or maintenance will result in the build up of harmful levels of ozone inside your house. Since there are many available air cleaners that don't produce ozone, I don't see a reason to choose a model that may pollute your air.

Thursday, December 21, 2006

Tobacco smoke in apartment buildings

I live in a small apartment building. When I come home after work, I smell cigarette smoke in my apartment, which I think comes from my downstairs neighbor. How can I get rid of the smell?

Cigarette smoke can come into your apartment from other apartments in many ways. The amount coming in usually depends on the ventilation in your apartment and the building, the weather, and cracks in walls and floors. Once in your apartment, the smell of tobacco smoke can linger, as it can can be absorbed into clothing and furniture.

Other than getting your neighbor to stop smoking inside the building either through persuasion or legal remedies, it will be difficult to prevent the smoke odor from entering your apartment. If you have a forced air ventilation system in your apartment, the odor may be entering your apartment through the vents. If so, the maintenance person for your building may be able to reconfigure your air handling system, which may help reduce or eliminate the odor. Otherwise, you could put an air cleaner (or two) in your apartment. Depending on the type or brand that you use, the air cleaners will remove the small particles from cigarette smoke, but they are not likely to do much (if anything) about the smell. You could also hide the cigarette smell with air fresheners. [For me, this remedy would be less than satisfying, since you would have an additional smell to deal with and since the cigarette smoke would still be getting into your apartment.]

What distance is a "safe" distance from a highway?

I have read, with great interest some of your statements and a presentation of yours on indoor air pollution resulting from close proximity to highways. My wife and I are considering a relocation, in order to decrease my commute time. However, almost every property we look at is within 1.5 miles of a major highway, which is often congested with trucks, etc. I have read over 10 studies documenting increased risk for childhood leukemia and asthma. What is considered a"safe distance" from a major highway? These studies don't state the exact distance at which they measured. Also, I have read of the ability of plants such as bamboo and areca palm in removing 80% of benzene in the air. Have you read those claims and do they seem to be valid?

You are right that many recent studies have shown that pollution from traffic, especially diesel-powered traffic (such as trucks) is bad for health. Traffic pollution has been linked to increased death and hospital admissions for heart and lung disease, increased asthma attacks, and early indicators of cardiac disease. Consistent with these findings, several studies have also shown that living near a major highway or road presents greater health risks. While there have been some differences among studies, there seems to be a general consensus that the critical distance from a busy road or highway is within 100 meters (or about 300 feet). After this distance, you generally no longer see a dramatic increase in traffic-related pollution above urban background. In a city, however, it is difficult to get away from all traffic-related pollution as it can travel relatively long distances.

It is not clear what pollutant or pollutants emitted from motor vehicles are responsible for the observed health problems. It is possible that plants (such as bamboo) under certain conditions can be used to remove certain gaseous pollutants from motor vehicles, such as benzene, carbon monoxide and nitrogen dioxide. I haven't heard of any plants that remove particles from motor vehicles. l think that most of the studies examining pollutant removal by plants have been conducted in closed environments. The effectiveness of using plants to clean your air in your yard will probably be much lower, as outdoor air moves pretty freely.

Who am I?

I am a professor in environmental health and I study how pollution affects people's health. Over the course of my career, I have received many phone calls and emails from people asking for some advice or information about an environmental problem that they are having. I know some of the people who contact me, while others I do not. The people that I do not know must go through a lot of trouble to get my contact information, by searching the web or reading scientific papers or books.

From these contacts and from personal experience, I know how difficult it can be to find trustworthy and practical information about environmental health problems. To make it easier to get information and to help others facing similar problems, I have decided to post any questions that I receive and my responses in this blog. This information is just my interpretation of available information and should not be taken as the only viewpoint or solution to a problem. Having said this, please feel free to post any of your environmental health questions. I will do my best to respond!