The Stratosphere Lounge | Episode 322

When it comes to knowing everything in the water, that may never be possible. Our technology keeps improving, so we’re always catching up in our ability to detect what’s in the water.
Chlorine is measured in parts per million, or milligrams per liter. We’re allowed 4 PPM in our water.
Metals are often measured in parts per billion, or micrograms per liter.
A lot of organics, such as perfluoroalkyl substances (PFAS) are being measured in parts per trillion, or nanograms per liter. (So, for that matter is NDMA.)
I expect soon we’ll see chemicals monitored and regulated at the parts per quadrillion level, or picograms per liter. (Well, we already do. Radioactive materials are measured and regulated in terms of picocuries per liter. A microcurie is about a third of a microgram. A picoCurie is about a third of a picoCurie is about a third of a picogram. That means in the case of uranium, we’re looking at regulatory limits on the order of picograms per liter, or parts per quadrillion.
A liter of water is some 55.5 moles. A mole is 6.02 X 10^23 molecules, so single molecules in one liter of solution are roughly equivalent to parts per octillion, or septillionths of a gram per liter.
If we’re doing the kind of complete analysis of water you’re looking for, a sample of 99% pure water could easily generate a list of 500 sextillion different components. Even if we have the technology to analyze every molecule in a liter of water, we still won’t know everything that’s in our water, because our brains just won’t hold it all.
And of course, in order to measure down to that level, we need to sample liters of water.