Most factories thankfully have stopped dumping oils, solvents, and other chemicals into rivers, lakes, and streams.

But today caffeine, antihistamines, and other household and agricultural chemicals are likely widespread even in crystal clear water running through seemingly pristine wildernesses, new research has found.

Tests of 38 waterways from the remote West Clear Creek in Arizona to the Chicago Drainage Canal discovered hundreds of so-called “emerging contanimants” that scientists increasingly view as ecological threats and potential public health hazards, according to a study published in the journal Environmental Science & Technology.

The scientists tested for 719 chemicals, said the study. Some streams contained only four compounds. Others contained as much as 161. But researchers discovered more than 400 of the compounds at least once.

Pharmaceuticals and pesticides comprised half of the pollutants found in the waterways, said Paul Bradley, a US Geological Survey hydrologist who co-authored the paper. Two-thirds contained traces of the antidiabetic drug metformin — marketed as Glucophage and other brands. Detergents, industrial substances, and other toxins made up the rest.

Bradley likened the study to “reconnaissance” that took a single snapshot of the streams as a first step in figuring out how the chemicals might affect living organisms, especially insects at the bottom of food chains that end with a fish on a plate.

That line of inquiry is especially important today.

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Unlike old-school pollution — think dyes from textile mills — banned under federal clean water rules enacted between the 1940s and 1970s, pharmaceutical and pesticides are designed to alter life, said Bradley.

What’s more, in the same way that doctors ask their patients about the drugs they’re taking to avoid harmful interactions, the chemicals that Bradley found could also be mixing and matching potentially into millions of other combinations, he added.

“We’re talking about organisms that are living in these streams,” he said. “They are not just visiting. Exactly how complicated and what kind of contaminants are showing up in a mixture and what is the effect of all those contaminants at once on an ecosystem or an organism?”

John Jackson, a scientist at the Pennsylvania-based Stroud Water Research Center, who was not involved with the study, said the research could explain why many waterways have not bounced back after factories stopped dumping toxins into them.

“The condition of the waterways where we have data are quite often much better than they were 40 or 50 years ago,” said Jackson. “But at the same time, it may help explain why we are not seeing some of the improvements we might be looking for.”

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Meanwhile, said Bradley, the source of the pollution is no secret.

Sewage treatment plants don’t filter out pharmaceuticals from human urine and feces before they clean and pump that water back into ecosystems. Pesticides and herbicides, meanwhile, drain from farmers’ fields and suburban lawns with few restrictions.

“Many of these compounds are not regulated,” said Bradley. “We don’t necessarily have to live this way. We can adopt more green chemistry. We can design more compound that don’t last as long in the environment. There are alternatives out there. We just have to decide it’s important enough to do.”

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