Medicines in tap water: what the tiny traces mean in pregnancy and for babies

Traces of medicines turn up in some drinking water, at levels thousands of times below a single dose. The risk is considered very low. Here is why scientists still watch it for pregnancy and babies, and what anyone can do.

Traces of medicines — painkillers, antibiotics, anti-epilepsy and mood-stabilising drugs, hormones — are found in rivers, groundwater and some drinking water around the world. Of all the contaminants on our homepage, this is the one where the honest answer is the most reassuring: the World Health Organization concluded that appreciable harm to health from these traces is very unlikely.

The amounts are tiny. They are measured in nanograms per litre — billionths of a gram — and are typically more than a thousand times below the smallest dose a doctor would prescribe. One analysis worked out that it would take between 3.4 and 34,000 years of drinking tap water to swallow a single dose of the medicines it looked at.

So why write about it at all? Because “very low for a healthy adult” is not quite the same question as “very low for an unborn baby or a newborn”, and scientists are careful to keep the two apart.

Why pregnancy and early childhood are treated differently

Babies drink more for their size. Infants and young children drink far more water for their body weight than adults, so their exposure to anything in the water is higher. One analysis put children’s relative risk at up to eight times an adult’s.
Their bodies clear medicines more slowly. A fetus or a newborn has immature liver enzymes and kidneys, which is why many medicines are dosed differently for babies, or not given to them at all.
Medicines that are never given in pregnancy. Some of the drugs detected in water are ones doctors avoid in pregnancy, or have not established as safe for children. At trace levels this is a theoretical concern, not a demonstrated harm.
Mixtures. Most safety assessments look at one medicine at a time. What many years of very low exposure to many different traces together might do is not well understood, and that is the main reason research continues.

Hormones in the water

Hormones attract the most attention, because they act at very low doses — the synthetic estrogen from contraceptives, and the natural hormones that people and farm animals excrete. The finding here is reassuring as well. A US risk assessment found that a child takes in about 150 times more estrogen from milk than from drinking water, and concluded that the estrogens in drinking water are not causing harm, even in the most sensitive groups.

Antibiotics

Traces of antibiotics raise a different question. The concern is less about the person drinking the water than about bacteria in rivers and wastewater becoming resistant to the drugs, which is a problem for everyone and a reason to keep antibiotics out of the water in the first place.

How medicines get into water

Through our bodies. The body uses only part of most medicines; the rest leaves in urine and passes into the sewers. This is by far the main route, and it is nobody’s fault.
Down the toilet or the sink. Unused medicines used to be flushed away. The advice now is to take them back instead: in the United States the FDA recommends a drug take-back point for almost all unused medicines.
Farming and manufacturing add some too, through livestock manure and factory discharges.

What you can do

Keep taking the medicines you need. Nothing about trace residues in water is a reason to change a prescription, in pregnancy or at any other time. Questions about medicines are for your doctor, not the tap.
Return unused medicines to a pharmacy or take-back point rather than flushing them.
If you want to lower your exposure anyway, activated carbon and reverse osmosis filters at the tap remove much of these traces, along with other contaminants on our list.

Why this matters to us

The Foundation funds water systems for children’s homes and shelters in Greece, and in New York and New Jersey we are building partnerships with organisations that house pregnant women, young mothers and their babies. We would rather tell them the truth than frighten them. On this contaminant the evidence is mostly reassuring, and the risks that matter more, such as lead, arsenic and bacteria, are the ones we test for and treat first.

If you would like to help us bring clean water to more mothers and children, the ways to give are on our donate page.

Sources

World Health Organization, Pharmaceuticals in drinking-water (2012).
Collier, Pharmaceutical contaminants in potable water: potential concerns for pregnant women and children, EcoHealth (2007).
Caldwell et al., An assessment of potential exposure and risk from estrogens in drinking water, Environmental Health Perspectives (2010).
US Environmental Protection Agency, Relative risk of pharmaceuticals in wastewater (research summary, archived 2017).
US Food and Drug Administration, Where and how to dispose of unused medicines.