Mexico, Swine Flu, and Pollution: Is There a Link?

Let me start this post by noting that, just as I am not a lawyer, I am neither a doctor or a scientist. But as those of you who read my posts (or my day blog) know, I am rarely inhibited by my ignorance.

Here's a thought about the swine flu pandemic, one I haven't seen elsewhere. To date, cases in Mexico have been far more severe than elsewhere. Many Mexicans are dying, while those affected elsewhere are, for the most part, recovering -- even though they're catching the same virus.

That got me to thinking: what could be causing the difference? I'm sure there are many, but let me suggest one that scientists may be overlooking: air pollution.

Mexico City, Mexico, ranks No. 5 on this year's list [of most polluted cities]. 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.

The WHO standards are fairly complex, and I'm not sure I could summarize them accurately. So at the risk of mixing apples and oranges, permit me to instead use the EPA's 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 on any day when the AQI exceeds 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."

Now look at this WaPo story from Monday:

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.

Given the fact that Mexico City fails to meet WHO standards three hundred days a year, it's plausible to conclude that the AQI in Mexico City consistently tops 300, which the EPA describes "hazardous conditions." Were that to happen in a U.S. city, the EPA would issue "health warnings of emergency conditions [as t]he entire population is more likely to be affected."

Here's some more info on conditions in Mexico:

Mexico City is one of the world's largest metropolitan areas, housing nearly 21 million inhabitants within the Valle de Mexico. . .The Metropolitan Area of Mexico City, also called Zona Metropolitana de la Ciudad de Mexico (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." . . .

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 had to say even before it added the warning on swine flu:

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 pollution is particularly bad from December to May, it's probably because that's the driest time of the year. Once the rains come, they help reduce (but not eliminate) air pollution.

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). It is surrounded by mountains, creating ideal conditions for temperature inversions, which keep pollution in and fresh air out. It has most of Nepal's factories, none of which come close to meeting U.S. environmental standards. And it has a thousands 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 the cost of doing business.

So I don't think it's a mystery why people are dying in Mexico City and not elsewhere. Their immune systems already are compromised thanks to the 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 take time to explore whether there is a connection. As WHO director Margaret Chan warned today, global health crises always hit less developed countries much harder than wealthy ones. If air pollution is part of the problem, the world's poor will be the ones to suffer the most.

Comments

[JC Armand]

Well there's no doubt that we need to clean-up air pollution, but with regards to the H1N1 virus I think the data is so scarce we really can't read anything into it. There have been approx 150 flu deaths in the country of Mexico, only 8 of those deaths have been to be confirmed H1N1 Virus, of which only 5 have occurred in Mexico City, a city of 30 million people. Also, I'm not sure how recent your EPA data is, but Mexico City has become much less polluted in recent years. I live in LA and travel frequently to Mexico City and I can't say on any given day that the air is cleaner here than there. To me it seems like there has been a vast overreaction to this whole thing by the media, check out this article from Dr. Mercola:
http://articles.mercola.com/sites/articles/archive/2009/04/29/Swine-Flu.aspx

[richmx2]

Add to not being a scientist or a doctor not being familiar with Mexico, or Mexico City. The reason there are more healthy young male fatalities (and the number of fatalities due to H1N1 virus has dropped as autopsy results are discovering other causes among suspicious deaths) is that deaths among healthy young people are more likely to be investigated than deaths among the old, the infirm and infants.

Air pollution COULD play a role in the deaths of already very ill persons (with lung cancer or asthma or other conditions that weaken the immune system), but not here.

[armando garcia]

Interesting but i dont think its accurate since we have had fatalities in cities where contamination is not the issue.

For me, the reason for having more deaths in Mexico compared to the US is simple... during the first couple of weeks of the outbreak, people who got sick in Mexico did not go to the hospital until it was too late (or were not properly diagnosed).

[stevesrant]

Thanks Charles for stating (some) of the obvious. Of course pollution has something to do with it. You don't need to be a scientist to know this, it's common sense. Any of us who remember what American cities were like before the Clean Air Act could tell you that. Don't know if it's still the case, but most of the cars in Mexico used to be diesel burning as well(like our trucks still are, why I don't know, but could guess...) which spews more heavey metals than gasoline. Add to this the inevitable malnutrition resulting from more widespread poverty, and the lack of medical care available to the same impovrished portion of the population, and you get more disease and death. Here in the comparatively cleaner and afluent US we know, through dozens of information outlets, up to the minute numbers of confirmed cases, where they are, and what medicine to buy.
While the Valley of Mexico plays a large part in trapping the polluted air, the air there is far more polluted to begin with. Every time I hear about reducing our carbon footprint to save the environment I say, how about simply producing less smoke so we can breathe cleaner air?