1.   As the water becomes overloaded with nutrients, the algae spreads and oxygen levels fall.

2.   Pollution levels have fallen slightly.

3.   The district tests the water and adds chloramine if levels fall below standards.

4.   The level of violence fell dramatically during the period of the ceasefire, although each side accused the other of extensive violations.

5.   Plasma cortisol levels did not fall significantly in the fluticasone propionate group, although there was marked suppression in the prednisolone group.

6.   The state of emergency was lifted a few days later after pollution levels had fallen.

7.   Part of the brain contains many oestrogen receptors and when oestrogen levels fall, mood changes may occur.

8.   Similarly, if the price level should fall, the real wage would rise, creating an excess supply of labour.

9.   Already healthy Chinese computer demand is helping Dell maintain revenue levels as prices fall drastically worldwide.