01:31 pm
Swine Flu and Air Pollution: Connecting the Dots?
Let me start this post by noting that, just as I am not a lawyer, I am neither a doctor or a scientist. We do have a very fine scientist, Chris Larson, on our blogging team, and I hope he’ll write on this.
But as those of you who read this blog regularly, I am rarely inhibited by my ignorance, so permit me to offer one more thought about the outbreak of swine flu. As you probably know by now, cases in the U.S. and Canada have been far milder than those in Mexico. Most American and Canadian victims are recovering, while many Mexicans are dying of what, genetically, appears to be the same virus.
That got me to thinking: what could be causing the difference? What conditions in Mexico are unlike those found in the U.S. and Canada. There are, I’m sure, more than a few (as with any two countries), but I’m going to focus on one: air pollution.
Mexico City, Mexico, ranks No. 5 on this year’s list. Residents can thank industrial and automobile emissions for air quality so bad that city ozone levels fail to meet World Health Organization standards an estimated 300 days of the year.
You can find the WHO standards here. They’re fairly complex, so instead of trying to parse them (Chris, white courtesy phone please), let me mix apples and oranges. The EPA has what it calls an Air Quality Index (screenshot via the EPA):
Anyone who lives in a big city in the U.S. has lived through a code red day — when people with asthma and those with weakened immune systems (such as the young and the elderly) are told to stay inside. In fact, the EPA warns that when it comes to anything above 150 100, “people with lung disease, older adults and children are at a greater risk from exposure to ozone, whereas persons with heart and lung disease, older adults and children are at greater risk from the presence of particles in the air.”
So people with impaired lung function are particularly affected by anything above 150. Now look at this WaPo story from this morning:
One theory is that the virus triggers an excessively aggressive immune response that destroys the throat and lung tissue. Young adults, with the most robust immune systems, may be especially at risk. . . . Most of the fatal cases involved extensive lung damage, requiring doctors to prescribe mechanical breathing assistance. Exactly what caused the lung damage is not known.
If my understanding of the WHO standards is correct, then the AQI in Mexico City consistently tops 300 — a.k.a. “Hazardous” for most of the year. The EPA describes hazardous conditions as “Health warnings of emergency conditions. The entire population is more likely to be affected.”
Here’s some more info on conditions in Mexico:
Mexico City is one of the worlds largest metropolitan areas, housing nearly 21 million inhabitants within the Valle de Mexico (also referred to as the Mexico City basin - see fig.1.5). The Valle de Mexico occupies ~1300km2 at a nominal elevation of 2240 m above mean sea level, and is bordered on the east and west by mountains that rise 1000 m above the valley floor, with low points to the north and south.
The Metropolitan Area of Mexico City, also called Zona Metropolitana de la Ciudad de México (ZMCM), lies in a high altitude basin almost completely surrounded by hills, mountains (including dormant/active volcanoes - seismic activity is frequent and the area which is well known as an “earthquake zone” but with an opening to the north that extends over 4 km2 and it is located 19°3′ north latitude and 99°1′ west longitude.
More than 20 percent of Mexico s entire population lives in the Valle de Mexico, and more than 30 percent of the country’s industrial output is produced within its environs. Though already one of the world s largest cities, the Mexico City metropolitan area is still growing at a rate exceeding 3 percent annually. More than three million vehicles travel on its streets daily.
And here’s what the State Department’s own travel advisory has to say:
In high-altitude areas such as Mexico City (elevation 7,600 feet or about 1/2 mile higher than Denver, Colorado), most people need a short adjustment period. Reaction signs to high altitude include a lack of energy, shortness of breath, occasional dizziness, headache, and insomnia. . . . Air pollution in Mexico City and Guadalajara is severe, especially from December to May, and combined with high altitude could affect travelers with underlying respiratory problems.
In case you’re wondering why it’s particularly bad from December to May, it looks like the rains come during the summer months, dissipating the pollution (if not eliminating it entirely). I used to spend a considerable amount of time in Kathmandu, Nepal. Just like Mexico City, the Kathmandu valley is located at a fairly high altitude (4,344 feet above sea level); is surrounded by mountains, creating ideal conditions for temperature inversions, which keep pollution in and fresh air out; has a high percentage of the nation’s factories, most of which would not even come close to meeting U.S. environmental standards; has a huge number of cars, motorcycles, and motor-taxis, all of which belch tons of CO2 and nitrous oxide.
Not coincidentally, every time — every single time — I traveled to Kathmandu, I got a sore throat within 72 hours of arrival. It often would be accompanied by coughing, but not other symptoms usually associated with a cold or flu. Everyone in the expat community had the same experience. It was considered part of the costs of doing business there.
In other words, I don’t think it’s a mystery why people are dying in Mexico City and not in the U.S. or Canada. Their immune systems already are compromised thanks to the amount of pollution they’re breathing in. I’ll even go so far as to predict that the death rate will fall once the rains come.
Again, I’m not a scientist. But here’s hoping those who are explore whether there’s a connection here. If so, it could help address the problem more quickly and reduce the panic that’s already spreading.