Human activities are making the earth saltier, from the soil to the water to the atmosphere, reports a study published Tuesday in the journal Nature Reviews Earth & Environment.

Salt pollution is not some “fancy” threat to our existence, like, say, a meteor hitting the Earth. However, the issue is not being addressed seriously while it is a “sleeping giant,” said Sujay Kaushal, lead author of the study.

Most people think of salt as the white powder we put on our food or the salt in the oceans, with the chemical name sodium chloride (NaCl). Sodium salt can also be found in detergents, other household products, and more, but there are many different salts, such as calcium, magnesium, and other ions used in additive products, all of which are growing in places where they wouldn’t normally be found.

Over the past 50 years, salt ions have increased in streams and rivers as people began using and producing more salt, the study says. The team found that across the globe, about 2.5 billion hectares of land – an area the size of the United States – has become saltier. Salt lakes also dry up and send elements into the air.

Increased salt concentrations could become “an existential threat” to our freshwater supplies, the study authors said.

Salt is a natural and necessary component of the Earth. The compound rises to the surface slowly over long geological time scales, through natural processes such as the weathering of sedimentary rocks. When exposed to the surface, the salt can mix with the water, be carried into the water, or become airborne. Living organisms, from plants to humans, take in small amounts that help regulate daily functions. Excess salt comes into contact with water molecules, seeping into groundwater, soil and oceans.

Human activities have changed this normal salt cycle in recent decades, the scientific team found. Agriculture, mining, construction, water and road treatment, and other industrial activities increase the amount of salt in the soil, drinking water systems, and air.