1.   Harmless powdery substances ranging from bath salts to baking soda to common mold now appear to be doing more to disrupt the mail than bad weather.

2.   Bild, however, reported that federal investigators had earlier removed the gunpowder and replaced it with a harmless substance.

3.   The powder was later determined to be a harmless substance.

4.   In some cases, the pollutants are broken down into harmless substances.

5.   Zirconium is a harmless substance which acts as a protective agent for nuclear material but is also used in the manufacture of jewellery and watches.