The existing guideline for lead, last updated in 1992, based its maximum acceptable concentration (MAC) of 0.01 mg/L (10 µg/L) on a provisional tolerable weekly intake of lead established by the World Health Organization (WHO) at a level that showed no increase in blood lead levels and thus no expected increase in health risks.

Recent studies of fractional deposition in humans have tended to validate the deposition model although particle deposition appears to be overestimated in the pulmonary region and underestimated in the trachea and bronchi.Water flashed into steam generating a destructive steam explosion and a subsequent open-air graphite fire.This fire produced considerable updrafts for about nine days.Visible light, the ultra-violet light we receive from the sun, and transmission signals for TV and radio communications are all forms of radiation that are common in our daily lives.These are all generally referred to as 'non-ionizing' radiation, though at least some ultra-violet radiation is considered to be ionizing.