This column has long made the controversial case that autism had a beginning, a "big bang" if you will. That moment was 1930 -- no U.S. cases before then fully match the classic description of the disorder.

Now let's take the next logical step: Not only did autism have a big bang, it also had a ground zero -- a place where many of the first cases concentrated before the disorder exploded nationwide. Ground zero was the nation's capital, in particular the Maryland suburbs where cutting-edge government research in the 1930s and 1940s exposed families to the chemical that first triggered the baffling disorder.

The foundation of this argument was laid out in the most recent Age of Autism column, "Mercury link to Case 2." Case 2 was known only as Frederick W., but we identified him as the son of a prominent plant pathologist named Frederick L. Wellman. At the time "Frederick W." was born, we showed, the senior Wellman was doing advanced work at the U.S. Agriculture Department's Beltsville research center in suburban Maryland, just outside the nation's capital.

Wellman was experimenting with plant fungi and ways to kill them, and his extensive archive makes clear one compound he studied was ethyl mercury fungicide -- the exact kind also used in the controversial vaccine preservative thimerosal, which many parents blame for the recent rise in reported cases (mainstream experts say it has been ruled out as a cause).

Ethyl mercury in both vaccines and fungicides was pioneered and patented in the 1920s through the work of Morris S. Kharasch. When Kharasch filed the first relevant patents, he was a chemistry professor at the University of Maryland in College Park, which actually adjoins the Beltsville research center.

More links to Washington are evident in other early cases described in 1943 by Johns Hopkins University child psychiatrist Leo Kanner, who first diagnosed the disorder in Frederick W. and 10 other children born in the 1930s. Reading between the lines of his landmark 1943 paper, the very first autistic child seen at Hopkins (in 1935) was "Alfred L.," whose father was a lawyer and chemist at the U.S. Patent Office. Also a clear connection to newly patented chemicals, the federal government and the nation's capital.

A child later profiled by Kanner was named Gary T. "Gary originally lived in Philadelphia," Kanner wrote in 1951. "The family then moved to Greenbelt, to Chicago, and back to Greenbelt."

Take a look at Greenbelt, Md.: It also abuts the Beltsville agricultural center in the Washington suburbs.

Recently, a mutual friend in Washington introduced me to a 58-year-old man with Asperger's disorder, the milder version of autism. We got together for lunch, and when I asked where in the Washington area he lived, I was both startled and somehow not surprised: Riverdale, Md. That's another Washington suburb that clusters with the College Park-Beltsville-Greenbelt dots I was already plotting. What's more, he was born there in 1948 in the same house he lives in now.

I asked what his father did. He told me he was an engineer. That fits a stereotype of Asperger's affecting kids of scientists and engineers -- the so-called "geek syndrome," nerdy brainiacs hooking up to somehow spawn a generation of kids with "autism lite." I asked him what kind of engineer his father was. The answer: a mechanical engineer who tested guns for the Navy at the time he was born.

And where was that? At what is now the Naval Surface Warfare Center in White Oak, Md. -- just a hop and a skip across I-95 from the Beltsville agriculture center.

I already had come across his father's line of work. In a 1972 paper, Kanner talked about a child named "Walter P.," born in June 1944. His father, too, was "an ordnance engineer for the federal government."

Kanner didn't say where Walter P. was from, but the similarity makes me wonder. Mercury fulminate was widely used as a detonator for explosives and armaments. Could those two fathers, like Frederick W., be linked to cutting-edge research involving mercury? (My Riverdale acquaintance said his father sometimes brought containers of mercury home from the weapons center for the kids to play with.)

And is that kind of research a reason Leo Kanner, at Johns Hopkins in nearby Baltimore, started seeing cases of this "markedly and uniquely" different disorder in the 1930s and 1940s?

Just last week I got an e-mail from the mother of a child with autism who lives on the other side of the country; her son was born nowhere near what I'm calling ground zero. But as I outlined this idea to her, she had a shock of recognition:

"I lived on a farm in Burtonsville, Md., while young and it is near Beltsville. The farm was surrounded by forest and abutted the Patuxent River."

Of course, not all the early cases cluster this way. But of the two other original "Kanner kids" from his 1943 paper that I've been able to identify along with Frederick W., one grew up in a town called Forest, Miss., a center of timber farming and planting; the other was the son of a forestry professor at North Carolina State University. Ethyl mercury fungicides were used to treat seeds, saplings and lumber in the 1930s, and in both places (as well as in Beltsville) the newly launched Civilian Conservation Corps was hard at work planting trees, cutting timber and building things with it.

To sum up: The first cases of autism seem to radiate outward from a central point -- as big bangs tend to do. As those exposures expanded, so did autism.

This suggests a new and deeply disturbing truth about the Age of Autism: our fate is not in our genes, Dear Brutus, but in the chemicals that increasingly pollute our world and our children.