These common prescription drugs include valsartan, losartan, and irbesartan in different combinations and from different manufacturers. The latest recall came Jan. 2, when Aurobindo Pharma USA announced it is recalling 80 lots of Amlodipine Valsartan Tablets USP, Valsartan HCTZ Tablets, USP and Valsartan Tablets USP.

Almost 60 million prescriptions were written for losartan drugs in 2016 and 14 million for valsartan or a drug that includes it. Another 3.6 million prescriptions were written for irbesartan that year. Here’s what you need to know.

What blood pressure drugs have been recalled?

Valsartan. There have been so many types of valsartan recalled this year that the FDA has created a website listing just for them.

The agency has also created a page that lists the drugs that have not been recalled.

Losartan. In December, the FDA announced a voluntary recall of losartan potassium tablets USP.  An addition eight lots of Torrent Pharmaceuticals’ losartan tablets were added to a previous recall in January. See which products were affected by the recall.

In November, the FDA announced a voluntary recall of losartan potassium/hydrochlorothiazide, 100 mg/25 mg tablets in 1,000-count plastic bottles, NDC 0781-5207-10, Lot number JB8912, Exp. Date 06/2020.

Irbesartan. In July, the FDA announced a voluntary recall of irbesartan tablets. See which products were affected by the recall.

Why are the drugs being recalled?

In each case, a recalled drug was contaminated with either N-nitrosodimethylamine (NDMA) or N-nitrosodiethylamine (NDEA).

Both chemicals are believed to cause cancer in humans. Research also suggests NDEA can cause liver and blood cell damage.

NDEA is used to make rocket fuel and can also be found in some food and drinking water, but at low levels. It can also be a created through certain chemical reactions and as a byproduct of industrial processes.

What is the risk of getting cancer from one of these drugs?

The FDA says it is very small. The amount of NDMA found in the recalled valsartan drugs exceeds acceptable levels. Records from drug manufacturers show the impurity may have been in the valsartan products for up to 4 years. The FDA estimates that if 8,000 people took the highest valsartan dose, which is 320 milligrams, from recalled batches every day for 4 years, there would likely only be one additional case of cancer over the life of those 8,000 people.

For context, 1 in 3 people in the United States will be diagnosed with cancer in their lifetime.

What’s driving the spike in recalls?

A common thread among all of these recalls is that the drugs, or ingredients in the drugs, were all made in China or India.

American drug companies since the 1990s have increasingly used factories in other countries to manufacture their products. About 40% of finished medications are made overseas, the Government Accountability Office says. Nearly 8 out of 10 active pharmaceutical ingredients, which are made into pills at other plants, are, too.

This globalization of the nation’s drug supply helps keep prices down, as it is cheaper to have them made in other countries. But with lower costs sometimes comes lower quality control.

What’s being done about products made in other countries?

An FDA spokesman says the agency is still investigating how these drugs became contaminated. Inspectors believe contaminated compounds were unintentionally created through a chemical reaction.

What should people who rely on these medicines do?

Experts say anyone taking a recalled drug should continue to do so, but contact your doctor or pharmacist immediately. The threat from the contamination may be less than the threat of not taking the drug.

Your doctor or pharmacist can help you find an alternative. But at least one expert says the recalls are making it more difficult to find valsartan drugs that have not been recalled. And, he says, some blood pressure drugs not on the recall list have seen price increases as demand spikes.