30 and Above. Get the 5 stage reverse osmosis system.
Health effects of Selenium on humans.
Short-term: Selenium is an essential nutrient at low levels. Exposure to low levels of Selenium can cause hair and fingernail changes; damage to the peripheral nervous system; fatigue and irritability.
Long-term: Long period and high exposure of Selenium can cause the following: hair and fingernail loss; damage to kidney and liver tissue, and the nervous and circulatory systems.