The human body is composed of around 66% water. Even mild dehydration of only 2% can decrease performance by 20%. It is recommended that people drink at least 1.5 liters of water per day. In developing countries, 80% of illnesses are caused by water-related diseases since 90% of wastewater is discharged untreated into waterways. Most of the planet's water is saltwater, while the majority of freshwater is locked away in polar ice and unavailable for human use. While access to clean water has doubled over the last 20 years, 1.1 billion people worldwide still lack safe drinking water.