Revelation 8:10,11

10 And the third angel sounded, and there fell a great star from heaven, burning as it were a lamp, and it fell upon the third part of the rivers, and upon the fountains of waters;

11 And the name of the star is called Wormwood: and the third part of the waters became wormwood; and many men died of the waters, because they were made bitter.

When the third angel sounds another large part of this comet hits the northern hemisphere* on the land surface of the earth and all the rivers and springs on this third of the earth are poisoned by the material the comet contains or by the material it kicks up into the atmosphere and then rains down on the earth .

Many men died because they only had water poisoned by the dust to drink. The fact that many people died would indicate that the waters would stay poisoned for some length of time. The passage also makes it clear that this body came from the heavens because the passage says it falls from heaven as a burning lamp. The passage even gives this body a name. The star that hits the earth is called  Wormwood  (wormwood was a Hebrew word that meant bitterness and the word is also used by the Greeks to describe a drink as being bitter and undrinkable). Today certain religious mystics are looking through telescopes expecting Wormwood to appear at any time. When a comet fitting their expectations does appear the watchers certainly will make sure the media calls the body by its appropriate name.

*(The third of the earth this refers to is probably two thirds of the northern hemisphere. For a comet to hit the earth and spread debris over a third of the earth it most likely will hit on the hemisphere where most of the land is. The northern hemisphere is 50 percent land mass and the southern hemisphere is only 25 percent landmass. A comet or meteorite would not spread debris over a third of the land surface of earth unless the debris was caught in two prevailing wind patterns. The Westerlies and Easterlies in the northern hemisphere fill the bill because these two wind patterns cover most of the northern hemisphere and about 1/3 of the landmass of the earth if you exclude the landmass in the northern hemisphere that occupies the Doldrums. The northern hemisphere is also where most of the persecution of God's saints took place, so it would be the appropriate place to receive the judgments from the wrath of the Lamb.)