There was a big story a couple weeks ago in China; the most comprehensive survey of pollution in China was released, and it showed a far worse picture of water health than previously estimated. This first national pollution census revealed that China’s water was twice as polluted as previously thought.

The main reason for the big difference was obvious; for the first time, officials included agricultural runoff, which is often loaded with pesticides, fertilizers and heavy metals. Here’s a good quote from the article (Chinese Pollution Census Reveals Greater Reach of Water Contamination – NYTimes.com):

…government planners had estimated that the country’s rivers and lakes could handle only 7.4 million tons a year of chemical oxygen demand. The scale and significance of agricultural effluent was seldom recognized in previous government planning, which focused on bringing down mainly industrial emissions to around 7 million tons a year from 13.8 million tons, said Mr. Ma, a leading expert on water pollution in China.

The new total of more than 30 million tons suggests a much bigger problem. “We believed we needed to cut our emissions in half, but today’s data means a lot more work needs to be done,” Mr. Ma said.

Why Do I Post This?

Well, from my family/community doctor perspective, this study highlights again the increasing dangers of China’s water, and I always am concerned about food safety, especially fish.

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Many of us rely on the Air Quality Index (AQI) supplied by the US Embassy as a guide to pollution levels in the capital. In this, the first in an occasional series of posts on this topic, I will discuss how to interpret this number in a Beijing context.

There are air quality standards and indices for several different urban pollutants, including dust particles of different sizes and gases such as NO2 and SO2. From epidemiological studies carried out in the last decade ultrafine dust (less than 2.5 microns in size) has emerged as the most important health risk, while pollutants such as nitrous oxide and sulfur dioxide that were once thought to be a problem for city dwellers have shown less correlation with health effects. The Embassy monitoring station measures these ultrafine particles, usually called PM2.5 that come from engine exhausts and industrial smoke. As far as current knowledge is concerned it represents the most useful guide to our exposure to pollution.

The simplest way to use the daily pollution reading (available on this site and on http://iphone.bjair.info/) is to focus on the brief risk assessment that accompanies each number, ranging from “Good”, through “Moderate”, “Unhealthy for sensitive groups” and so on. But if you understand a little about the index and the numerical score you can get a clearer perspective on what it is telling you.

The AQI is a scale devised by the US-based Environmental Protection Agency (EPA). It is based on a standard for air quality set by the EPA, which considers an average amount of PM2.5 particles of 35 microgrammes per cubic meter to be the maximum acceptable exposure over a 24 hour period. This figure corresponds to an AQI on their scale of 100. The first point to notice is that this refers to an average, so a brief exposure to levels above 100 is not necessarily a cause for alarm if our overall exposure averages lower than this. Nevertheless 100 is a useful number to keep in mind: anything above this score is worth paying closer attention to.

The AQI scale was devised with US cities in mind, which mainly have their air pollution well under control. On a typical day most busy cities in the US score 50 or below, and the AQI scale is designed to be most sensitive to differences in pollution levels in the 0-100 range. Here are the ranges, their health descriptions and corresponding PM2.5 dust levels:

The sharp-eyed will notice that the relationship between the AQI and the amount of pollution is not a straightforward one. For readings above 100 the index increases more slowly with increasing PM2.5 dust level. To take an example, we might intuitively expect an AQI of 200 to reflect double the level of pollution of an AQI of 100, but in fact the total amount of dust has already doubled by the time we reach 150. At an AQI of 200 the pollution level is FOUR times the level at AQI 100. This point is worth bearing in mind in Beijing since we often experience AQI scores in the range of 100 to 200 (or more).

To sum up, days with AQI scores below 100 correspond to relatively low exposures to dust particles, but above 100 the exposure is increasing significantly. I will address the question of what the numbers mean in terms of our health in a later post, but as a rule of thumb I will consider a bicycle ride or jog outdoors on days with an index below 100, but when the index is above 150 I will be postponing that exercise for another day.

For more information on this scale and how it is calculated consult the AirNow website:

http://www.airnow.gov/index.cfm?action=aqibasics.aqi

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There are three plants in particular, which you can see in this link (Natural Indoor Air Purifiers – How To Grow Indoor Fresh Air With Plants, Nature’s Air Filters). They are the snake plant, golden palm and money plant. Fortunately, these are both very common and inexpensive. This combination of plants is especially effective as they combine different functions to clean air of toxins both night and day, as well as to add pure oxygen. This was studied in a 1989 NASA study (PDF file) and was recently discussed in a TED Conference video from India, where scientists used an apartment complex as a trial and found strong improvements in people’s indoor air. Here’s a quote:

These three plants where tested for 15 years at Paharpur Business Centre and Software Technology Incubator Park in New Delhi, India. The building is 20 years old, 50,000 square feet, employing over 1,200 plants for 300 working occupants. The Parharp office building is rated the healthiest building in Delhi by the Government of India. This study was published on September 8, 2008 by The Goverment of India, Central Pollution Control Board and Chittaranjan National Cancer Institute, Kolkata, India

The study found that there is a 42% probability of increasing blood oxygen by 1% if one is inside the building for 10 hours. Compared to other non-planted buildings in Delhi, the Parharpur Office Building showed reductions of:

Eye Irritation – 52%
Respiratory Conditions – 34%
Headaches – 24%
Lung Impairment – 12%
Asthma – 9%

15% in energy costs where saved by injecting much less that the 15-20 cubic feet per minute of fresh air into the building as suggested by ASHRAE industry standards. This is significant considering how 40% of the worlds energy is used to maintain all building environments.

The most surprising discovery in this study was a measured increase in human productivity of 20%, a result of fewer sick days and increased employee productivity.

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The best collection is from the U.S. EPA:

• SmogCity2: a fun and interactive game where you can control your city, like the Sims. There are two versions, one for ozone and another for particulates.
• Environmental Kids Club – they also have a section on air pollution
• AirNow: they have a series of pages for kids, students and teachers

Chinese Versions

I found a site from Taiwan: 空氣品質兒童網站

Anyone have other good links? Please share in the comment section below.

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Both the IQAir and Blueair air purifier companies offer free testing of your home, office or school. They will drop by with their handheld air monitor and give you the lowdown as to how bad or good your air is.

The Blueair team is run by Chris Buckley, who runs the Torana store (8459.0785; mobile 13910569358); his website is at Toranacleanair.com. The IQAir group has a few Beijing stores and a China website; telephone 8447.5800. Thanks to both for this good community service. If anyone else offers such a service, please let me know and I will add it here.

And for full disclosure, I own both a Blueair and an IQAir at home, and I am very happy with both. At work in my small office, I have a Hunter purifier from Sundan and like it a lot as well. I also feel that air purifiers are crucial for Beijing. And don’t forget about indoor plants!

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My goal in sharing this is to encourage all schools — all over China — to review their air pollution action plans. And if they don’t have a plan, hopefully this slide show can drive the discussion within your schools.

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(The following is a guest piece from Chris Buckley, owner of

Recently, I’ve been doing measurements inside and outside of homes in Beijing, looking at fine particle air pollution, of the same size range (less than 2.5 microns) that is monitored by the US Embassy. Most homes have indoor air pollution levels that are similar to outside levels, as Richard has mentioned in a previous post on Beijing air pollution, but in a few cases I have seen levels of fine dust that are much, much higher than outside. In one case recently the dust in the finest range that I am able to measure 0.3 micron to 0.5 microns) was 3 times higher than the outside air, and dust in the 0.5micron to 2.5 micron range was an astonishing 28 times higher than the outdoor level.

So what is going on in these homes?

In each case the common factor was the presence of ultrasonic humidifiers filled with Beijing tap water. These humidifiers work by making a fine mist with an ultrasonic vibrating plate in a water tank. They are popular and cheap to buy in Beijing, and at this time of year department stores are full of these machines, including whimsical designs in the shape of cartoon characters. The side effect that all ultrasonic machines share is that as this mist evaporates it leaves a tiny nucleus of hard water salts suspended in the air. It’s common in ultrasonic humidifers sold overseas for them to include a cartridge that removes the hard water salts, but models sold in Beijing usually lack this feature.

Most people who own these ultrasonic machines realize that if they put tap water into these machines they will get a deposit of white dust around their humidifier. What is less widely appreciated is that the machines not only make large dust that settles out rapidly but also produce dust at very small sizes, even in the 0.3micron to 0.5micron range. These particles stay suspended in the air a relatively long time and some of them will end up in our lungs.

To put this in perspective, mineral salts from humidifiers are not as much of a health hazard as the carbon soot from diesel engines and coal burning that are a well-researched hazard of city life. Opinions differ on the level of risk that humidifer dust poses: the problem for researchers is a lack of data, and the fact that the physical properties of materials change when they are converted to very fine dusts. The US-based Consumer Product Safety Commission sums it up on their website: “The health effects from inhaling this humidifier dust are not clear” I think it is safe however to say that humidifier dust places an avoidable extra burden on the lungs, especially in Beijing where we have so much air pollution to cope with anyway.

In talking with some ultrasonic humidifier users I have found that some believe that adding vinegar to the water takes care of the problem. This is based on the logic that vinegar can be used to clean limescale from a kettle. Unfortunately, in the case of ultrasonic humidifiers it does not help, since what goes into the humidifer must come out, so this just adds to the burden of salts in the dust, as well as evaporating vinegar into the air.

So what to do? For ultrasonic humidifier owners there are two safe options: use distilled or de-ionized water in the machine, or get rid of it and get a humidifier that works by evaporation rather than ultrasonic misting. De-ionized water contains no salts and does not make dust particles as the mist evaporates. This water is expensive however, so the best long-term solution for most people will be to use an evaporative humidifier, since these types can take tap water without creating dust.

In either case, you should also clean your humidifier each time you refill the tank, to prevent the build up of molds and bacteria, and periodically de-scale the machine if there is limescale build-up.

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Providing people with timely air quality information and educating them about the links between pollution sources, air quality, and health, can lead to a healthier and better-informed society. The ability to provide real-time data and air quality information and forecasts is critical to protecting public health. For many individuals—children, outdoor workers, and those who suffer from respiratory problems or cardiac conditions—knowing the quality of the air they breathe affects the quality of their lives and how they plan their daily activities. EPA’s AIRNow program has fulfilled this need for the past decade in the United States.

Developing countries are installing air quality monitoring networks and beginning to forecast air pollution levels to provide information to government officials and citizens. Effectively communicating information, educating the public about air quality conditions, and exchanging data with other organizations and systems will be critical next steps.

I think this is terrific news. In Beijing, of course, we are lucky to have an “unofficial” real-time monitor from the US Embassy station; but clearly the impact of all 20-something local pollution monitors providing hourly real-time data for all neighborhoods will be an enormous benefit to everyone. I’ve stressed many times that real-time data is crucial for people to make safe choices for outdoor activity, especially with schools needing to set up air pollution action plans by using the US Embassy data.

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Air pollution continues to be the most popular subject on this website. Now, there’s a great new review as well as a patient handout to explain the basics. It’s from my specialty’s Journal of the American Family Physician. They just published a great review (Outdoor Air Pollutants and Patient Health) which describes the main culprits of air pollution.

It also reviews pollution levels using the US EPA’s Air Quality index as well as action plan. This is exactly the same concept and table that the US Embassy uses in their pollution monitoring, which you can access via websites and iPhone apps. Notice how the recommendation states how levels over 200 are “very unhealthy” and that “everyone should avoid all physical activity outdoors“. How many of us do that? How many schools enact that plan? The graph is below:

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I haven’t downloaded it yet, so please let me know if there are problems…

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