Almost certainly, but only because no purification method is perfect and some quantity of contaminants will always be present; the concentration will depend on the purification process used. The treatment processes used in the USA involve several steps which ultimately produce a safe product. If greater purity is required or desired, other methods are available. For example, reverse osmosis (RO) uses membranes which ostensibly only allow water to pass through, but there are always imperfections. In practice, RO will remove nearly all organic material larger than viruses (which are much smaller than bacteria and human cells).

Distillation is another method and is relatively simple: water from some ("contaminated") source is evaporated, then the vapor is condensed in another container. Most of the undesirable (in this case, skin cells, but also bacteria, many chemical compounds, and other large particles) do not evaporate, so they are left behind in the source container.

On a related note, dead skin cells are everywhere and we ingest them by breathing ( study here, ) and any time we eat anything else. As briefly covered in the latter article, this could actually be beneficial by protecting against allergic reactions and perhaps contributing to inoculation.

People get their drinking water from different sources. In rural areas, people are more likely to get their water from private wells. Depending on local regulations, and the preferences of the homeowners, the water may be more or less filtered or treated. If an entire community shares a well, it is very likely that the water is treated and filtered, destroying and removing old cells.

Surface water (rivers and lakes) is also filtered and treated. There are federal regulations, but cities also make local decisions about treatment. I live in a city that had an outbreak of a parasite called Cryptosporidium in 1993 ( outbreak ). About a quarter of the city got sick. So citizens were willing to invest in ozone filtering to avoid any future outbreaks. Ozone filtering is expensive, but it kills the hardy crypto.

The real question is whether any cells are going to be in a treated water supply. As soon as cells die, they start to decompose. Not only do they break down on their own, microbes start decomposing them. Keeping a cell organized takes energy, and dead cells can no longer do any work. The molecules that make up cells (fats, proteins, carbohydrates, and such) are also broken down. Even the atoms that they are made of are usually removed from drinking water. There are limits, for example, on how much nitrogen is allowed in drinking water.

You may be wondering how some communities end up with toxic water. It could be because contamination levels are so high that they can’t be removed. For example, too much fertilizer from farm fields may end up in groundwater and seep into wells. In the case of Flint, Michigan, the lead and microbes contaminating the water were in the pipes themselves. When the city switched water sources, they didn’t change how they treated their water. The Flint River water was too acidic, and damaged the pipes.

What do you think are the biggest threats to our drinking water? Thanks for asking,

Probably? Drinking water is filtered to get rid of bacteria, viruses, and other potentially dangerous things from it, and those filters would filter out cells, too. However, if you stick your lips into a glass of water, I bet that some of the cells from the surface of your lips will peel off and wind up in the water.