1.   The dust contains a variety of minerals such as quartz, pyrite, dolomite, siderite, magnetite, and a variety of solicates.

2.   According to the World Book Encyclopedia, outdoor dust contains mineral material from plowed fields, river flood plains and the floors of deserts.

3.   House dust can also contain heavy metals, such as particles of lead from paint, and this can cause health and developmental problems in children, she adds.

4.   Many assume that the dust contains traces of human remains, and people are eager to scoop up samples to keep as a souvenir from the tragedy.

5.   The anti-pressure-treated wood people will scream at this suggestion, because the sanding dust contains arsenic.

6.   The dust contains calcium carbonate, which is nearly as caustic as lye, formaldehyde, carbon and sulfur dioxides and petroleum from burning plastics.

7.   The letters said the dust contained anthrax bacilli, but the local police said it was probably a hoax.

8.   Preservationists have said the dust may contain toxic substances that could damage the church.