MTBE is added to petrol in the US to improve combustion and reduce air
pollution. It is credited with halving emissions of the carcinogen benzene from
exhausts and its use has improved air quality in some of the country’s smoggiest
cities.

But the chemical has leaked into aquifers from thousands of underground petrol storage tanks
(This Week, 22 November 1997, p 24).
It is highly water-soluble and long-lived, and is classified by the Environmental Protection
Agency as a potential carcinogen. So disagreeable is its smell that even
minuscule amounts can render water virtually undrinkable.

Faced with contaminated drinking water supplies and increasing public
pressure to ban the additive, the state of California—the worst
affected— appealed to its universities for a solution. Ed Schroeder and
Juana Eweis at the University of California at Davis noticed that something in a
compost tray at a water treatment plant near Los Angeles was eating airborne
MTBE. Soil microbiologist Kate Scow and graduate student Jessica Hanson isolated
the bacterium responsible. The species has not yet been identified and is
currently known as PM1.

In laboratory studies, Scow injected the microorganism into samples of
contaminated soil. She found that at a concentration of a million cells per gram
of soil, the bacteria digest a dose of MTBE of 25 parts per million in about six
days.

Engineers have developed bioreactors for cleaning up contaminated water, but
cleaning up groundwater in situ may prove more difficult. For instance,
the researchers are still not sure how the bacteria will perform in the natural
environment when other chemicals are present.

“To be brutally honest, there are not a lot of examples of injecting
organisms into the groundwater working very well,” says Scow. “It’s a very
tricky problem.”

Next week the World Wide Web Consortium, the Web’s governing body, is
expected to give the new language, called MathML, a “recommendation”. This is
the closest it gets to defining a standard, and will essentially give software
authors the go-ahead to develop applications for MathML.

Mathematicians and scientists have been increasingly frustrated with HTML’s
inability to include mathematical expressions. To show an equation on a Web
page, researchers must create it in an editing program, save it as an image file
in a format such as GIF or JPEG, and embed the image into the HTML. Images take
a long time to load, and the equations can’t be cut and pasted like text. You
can’t index them, or search a database for parts of equations.

“Right now, you have to go through a lot of contortions,” says Jim Martino,
who teaches calculus at Johns Hopkins University in Maryland. As online books
and journals proliferate, so do these GIF files. The American Mathematical
Society says there are “around two million or so graphics on our Web server”,
according to the mathematician Ralph Youngen.

MathML is the result of more than two years of negotiations. As well as
capturing equations, it fits seamlessly into the software that mathematicians
and scientists already use. It was not easy. “People are quite fussy about the
way maths is presented, about the way it looks, about what they can do,” says
Patrick Ion, co-chair of the Web consortium’s working group.

However, MathML is not simple. “It’s not the sort of thing you really want to
edit by hand,” says consortium member Dave Raggett. The mark-up will have to be
encoded by software that will presumably included in equation editors.

MathML is an application of XML (eXtensible Mark-up Language), the successor
to HTML, which the consortium recommended on 10 February. “I think everybody
expects to see, in the long run, a wholesale migration to XML out of HTML,” says
Rob Miner, another co-chair of the working group that developed MathML. There
are already several prototype plug-in programs that adapt Web browsers for
MathML, says Miner. Eventually, plug-in programs won’t be necessary.