Aren't modern incinerators safe and reliable?

No. There have been risks involved in burning trash--especially since people throw such a variety of materials away. Some of these materials are highly combustible and explode when placed into an incinerator. In April 2007, a Covanta incinerator in Rochester, MA exploded--causing a major fire. Citizens were cautioned to seal off their windows and doors so that they would not be exposed to toxic fumes. The plant sustained heavy damage. It was a heavy toll on local fire fighters who rarely see such a massive fire. See the full story here: Unintentional fire at Covanta's SEMASS trash burner in 2007.
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Also, local governments are at risk for lawsuits from residents who are exposed to lead, dioxins and other contaminants. The Byker Reclamation Plant in Newcastle, England is an example of citizens facing extreme dioxin contamination. In response, the Environment Agency attempted to suppress investigation. The risk of not really knowing what citizens are exposed to until it is too late should be a troubling one for citizens and representatives alike: Byker Toxic Ash Accident and Cover-Up

Columbus, OH residents filed a lawsuit for overexposure to dioxin from their waste incinerator: http://www.lexingtonma.org/swat/Jun2698N.htm

Although they didn't win the lawsuit, why would local governments wish to invite mistrust and litigation from their own citizenry...when safer and less expensive alternatives are available? No one sues their local government over comprehensive recycling programs, and they reduce the volume of trash without pollution.

More on the Ohio story from Paul Connett:

"... in 1993, the citizens of Columbus, Ohio, who were aroused by anecdotal reports of an increase in rare neurological symptoms and other illnesses, including cancer, in the vicinity of a 2000 ton per day incinerator, discovered that measurements made at the facility in 1992, but not reported to the public, indicated that nearly 1000 grams of dioxin TEQs were being emitted from the facility annually (23). This was more than the total dioxin generated in the whole of Germany at that time. The citizens received two further shocks. First, scientists from the US EPA reported at Dioxin '93, that the total quantity of dioxin emitted from all the US trash incinerators combined (about 130 at that time) was between 60 and 200 grams of dioxin TEQs (24), which was less than the single Columbus incinerator by itself. Second, the Ohio Health department reported that a 1000 grams of dioxin (about one half of a Seveso accident) falling annually on their heads and surrounding areas posed no health problems (25)."

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