According to some figures, the consensus is that 70.8% of the Earth's surface is covered by water; 29.2 % is covered by land. Other figures suggest the percentage of Earth's surface covered by water is 71.11%; the percentage covered by land is 28.89%.
~ Only 3% of alll the water is fresh water, the rest is saltwater.
The earth is covered by water in 3/4 th parts.
About 66% or 2/3 of the Earth is covered by water.
=== there is about 72% of water covering the earth ===

Ocean water is about 3.5% salt.

It's a bit under 1% (about 0.9% is often quoted). Sea water is now almost 4% salt (something like 3.9%, though it varies from place to place). It has been pointed out that the percentage of salt in human blood is the same as the percentage of salt in seawater at the time the earliest life on earth was developing.

This is a brief list of the types of toxins in drinking water and what effects they can have on your health.

1. Chlorine – Can cause bladder and rectal cancers, and also asthma. Recently, experts have linked chlorine to breast cancer.

Health effects of chlorine

Chlorine is a highly reactive gas. It is a naturally occurring element. The largest users of chlorine are companies that make ethylene dichloride and other chlorinated solvents, polyvinyl chloride (PVC) resins, chlorofluorocarbons, and propylene oxide. Paper companies use chlorine to bleach paper. Water and wastewater treatment plants use chlorine to reduce water levels of microrganisms that can spread disease to humans (disinfection).

Exposure to chlorine can occur in the workplace or in the environment following releases to air, water, or land. People who use laundry bleach and swimming pool chemicals containing chlorine products are usually not exposed to chlorine itself. Chlorine is generally found only in industrial settings.

Chlorine enters the body breathed in with contaminated air or when consumed with contaminated food or water. It does not remain in the body, due to its reactivity.

Effects of chlorine on human health depend on how the amount of chlorine that is present, and the length and frequency of exposure. Effects also depend on the health of a person or condition of the environment when exposure occurs.

Breathing small amounts of chlorine for short periods of time adversely affects the human respiratory system. Effects differ from coughing and chest pain, to water retention in the lungs. Chlorine irritates the skin, the eyes, and the respiratory system. These effects are not likely to occur at levels of chlorine that are normally found in the environment.

Human health effects associated with breathing or otherwise consuming small amounts of chlorine over long periods of time are not known. Some studies show that workers develop adverse effects from repeat inhalation exposure to chlorine, but others will not.
Environmental effects of chlorine

Chlorine dissolves when mixed with water. It can also escape from water and enter air under certain conditions. Most direct releases of chlorine to the environment are to air and to surface water.

Once in air or in water, chlorine reacts with other chemicals. It combines with inorganic material in water to form chloride salts, and with organic material in water to form chlorinated organic chemicals.

Because of its reactivity chlorine is not likely to move through the ground and enter groundwater.

Plants and animals are not likely to store chlorine. However, laboratory studies show that repeat exposure to chlorine in air can affect the immune system, the blood, the heart, and the respiratory system of animals.

Chlorine causes environmental harm at low levels. Chlorine is especially harmful to organisms living in water and in soil.

2. Lead – Lead enters tap water through corroded pipes. Lead in drinking water is harmful for pregnant mothers and children. Lead poisoning has been proven to cause learning disorders and severe developmental delays.

3. Giardia and Cryptosporidium – These types of protozoa are responsible for widespread and severe outbreaks of gastro-intestinal diseases. They will make their way in the water system whenever here has been a sanitation breakdown.