Asthma is an urban disease, possibly affecting as many as one in four urban children, a much higher toxicology rate than in rural areas.  So naturally we deduce that something about urban buildings triggers asthmatic responses – but the causes have been much debated until a recent study fingers a likely culprit:

Hiding in plain sight?

As reported in the New York Times:

Asthma is the most common chronic disease of childhood, one that strikes the poor disproportionately. Up to one-third of children living in inner-city public housing have allergic asthma –

That asthma is more prevalent among urban children, then among poor urban children, then among public-housing urban children, strongly suggests that something about their living conditions is the cause. 

See a cause of asthma here?

–  in which a specific allergen sets off a cascade of events that cause characteristic inflammation, airway constriction and wheezing.

Since asthma is a breathing-irritation disease, we can posit that something in the air quality of poor apartments is unhealthy to children.

Now, using an experimental model that required leaving the pristine conditions of the lab for the messier ones of life, a team of scientists from the Boston University School of Medicine have discovered what that allergen is.

“For inner-city children,” said the lead researcher, Dr. Daniel G. Remick, a professor of pathology, “the major cause of asthma is:

Not dust mites

Ugly and rapacious, but innocent!

Not dog dander

Dangerous and spiky, but innocent!

Not outdoor air pollen.

Spikey and mathematical, but innocent!

It’s allergies to cockroaches.”

Guilty, guilty, guilty!

Dr. Remick and his colleagues (then at the University of Michigan) published their first paper in 2002, after developing their model over several years. Their laboratory was in Detroit, where, as in many other cities, public housing suffered from pest infestation.

The team made home visits with an old-time data-collection instrument: the vacuum cleaner.

Science at work

“We collected house dust — big dust bunnies — added water, let them mix overnight, and spun the junk out of them, until we had extract,” said Dr. Remick, now 56.

Just add water, and flee!

The things we do for science.

The extract was filled with proteins from Blattella germanica — the common cockroach — whose exoskeletons and droppings become airborne after death.

Stop shedding your exoskeleton, okay?

Back in the laboratory, mice were exposed to the dust bunny particles. After being injected, they were immunologically primed: their cellular response systems went on alert.

Better mice than men for this testing, to be sure.

A story of asthma?

When exposed to the same particles a second time by inhaling them, the systems on alert went to attack. Mice that had been breathing easily had difficulty exhaling, and their respiration slowed — a rodent corollary to wheezing. They were having asthma attacks.

This is classical science: conduct a repeatable experiment, observe the consequences.

Analysis of their lungs showed that their airways were clogged with white blood cells, mostly of a type called eosinophils, that caused mucus secretion, tissue damage and changes in muscle contractibility.

You try breathing that

Mice in a control group, exposed to dust mites instead of cockroach protein, had none of the same respiratory or pathologic changes.

Mice do not suffer from the placebo effect.

The team reproduced their results in several sites; different dust bunnies, same allergic reaction.

Reproducibility is what distinguishes science from alchemy.

“We’re pretty excited,” Dr. Remick said in an interview, “because this is the first time someone has actually taken stuff from houses where kids have asthma.”

From the New York Times: Remick offers you your choice of dust bunnies to inhale

Researchers not directly involved with the studies said they were excited, too. “It’s a clever thing,” said Dr. Lester Kobzik, a pathology professor at Harvard Medical School. “He’s collected the nasty material people actually get allergic to.  You can’t call up your chemical supplier of scientific reagents and say, ‘I would like five pounds of exactly the same house dust,’ ” Dr. Kobzik continued.  “Remick had a bucketload, so he could do several years’ worth of experimentation and study it carefully.”

By accumulating particular vintages of dust bunnies, Remick had samples large enough to repeat his experiment under widely varying conditions.

Dr. Peter A. Ward, a professor of pathology at the University of Michigan Health Services, who recruited Dr. Remick into residency almost 25 years ago, called the work “probably the closest thing in animal models to simulating what one sees in human asthma.”

Most laboratory asthma research still uses genetically created proteins to induce symptoms in mice; often, the proteins are taken from egg whites. This is scientifically pleasing, but less relevant to real life. Egg whites (which humans rarely grow allergic to) have little in common with the city dust children are more likely to cavort through and inhale.

Nothing like an egg white

Using the same mouse model, Dr. Remick is now studying the effects of various asthma treatments, including the anti-inflammatory drugs called tumor necrosis factor inhibitors, like Remicade and Enbrel. The drugs, already used for treating rheumatoid arthritis and inflammatory bowel disease, appear to derail a crucial immunologic compound that attracts eosinophils.

“Blocking tumor necrosis factor in a mouse model improves asthma,” Dr. Remick said. “It’s pretty slick.”

Trying to derail you guys

For affordable housing owners, managers, and residents, the implication is clear: clean up your kitchens and bathrooms, keep the roach population at bay, and you grow healthier children. 

Jay: [Steps on roach] Ooo, I’m sorry. Was that your aunty?

De-roaching housing may become more than just good common sense, it may become a hygienic or leasing requirement.

Time to check out the roaches

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