Ferrous iron. Arsenic. Boron. No, this isn’t a list of possible names for Gwyneth Paltrow’s next baby, but a few of the exotic contaminants that could be lurking in your water. The same water you drink and give to your plants!

Along with these baddies are ferric iron, iron bacteria, arsenic #3, arsenic #5, and even endocrine disruptors (EDCs) and pharmaceuticals and personal care products (PPCPs)! The truth is that understanding what’s actually in your water is of vital importance to your plants, your health and your wallet.

The most common of these—iron—leads us to…Michigan! Michigan is in the iron belt, which is part of the reason Detroit is the heart of the auto industry. A high level of iron in the soil is great for mining and metal manufacturing, but it’s not so great for the water.

Since the average gardener probably doesn’t have a graduate degree in chemistry, it’ll be helpful to drop a bit of science here before discussing the best way to rid your water of iron. Iron exists in two states in water called ferric and ferrous. Ferric means the iron has been oxidized, frequently by iron bacteria, while ferrous iron (also called dissolved iron) is not oxidized.

Orange gunk in a RO system’s pre-filters indicates the presence of ferric iron, as do rust stains in your sinks, toilet and bathtub. Orange gunk can also indicate the presence of iron bacteria, which create a slimy orange substance and can be tough to get rid of. Iron removal is tricky, as even 0.33 ppm can be bad for your plants and can prematurely foul RO membranes. Typically, removal requires a special media filter.

Methyl tertbutyl ether, also known as methyl tertiary butyl ether and MTBE, is an organic compound with the molecular formula (CH3)3COCH3. MTBE is a gasoline additive that prevents engine knocking and helps decrease engine emissions. Leaking underground storage tanks are usually the cause of groundwater contamination, and the substance causes an unpleasant odor and taste in water.

Once introduced, it spreads throughout groundwater easily due its solubility and removal on a municipal level can be very costly. The U.S. Environmental Protection Agency classifies MTBE as a human carcinogen in high doses, and its use is banned in California and New York. The good news? MTBE can be removed with a simple activated, coconut-derived carbon filter.

Although best known as an odorless, tasteless poison popular with murdering schemers throughout the annals of history, arsenic can also be found in your drinking water. This contaminant can be naturally occurring, but is also a by-product of environmental pollution and has been linked to organ cancers, headaches, nausea and a host of other health issues.

There are two forms: arsenic 3 and arsenic 5. Arsenic 3 is difficult to remove and must be oxidized and converted to arsenic 5, at which point it can be removed by RO filtration. Arsenic compliance laws require municipalities to ensure less than 10 ppb (parts per billion) in the water they provide, but private wells can contain this dangerous contaminant. A water test with an independent lab can determine the safety of the water.

Of increasing concern, and frequently in the news as of late, are EDCs and PPCPs. While some of these chemicals can be naturally occurring, most of them enter our water through industrial practices in agriculture and from us.

When we take prescription medications that are not fully absorbed or broken down by our bodies, these chemicals enter the hydrologic cycle through our waste water and are often hard for water treatment plants to get rid of. In the case of agriculture and livestock, pesticides and medications given to livestock enter the environment directly through runoff and drainage.

This water trickles into rivers and streams and join the hydrologic cycle as well. EDCs interrupt endocrine activity in animals and humans which can disrupt growth and reproductive activity.

Many of us are aware of Bisphenol A (BPA) in plastic and make efforts to avoid drinking and eating food packaged in plastic containing BPA. This concern is due to the endocrine disrupting effect of BPA and is why many companies have switched to BPA-free plastic.

Unfortunately, the water we drink can contain these insidious contaminants. Reverse osmosis can remove many of these contaminants, but must be utilized as point-of-use (household) filtration due to the expense of using RO on a municipal level.

One of the most difficult contaminants to remove is an element called boron. Although levels in drinking water are not regulated by the federal government, some states do have allowable levels. While most is naturally occurring, some boron contamination is a result of human activity.

Boron can cause rashes, dizziness, vomiting and a whole host of health problems with prolonged exposure. It’s important for gardeners to be aware of potential boron contamination, as even very low levels can be toxic to plants. Boron removal is difficult and complex, involving a specialty resin and other custom equipment, and is best facilitated by a professional.

These are just a few of the contaminants you might find in your tap water. While it’s important to know what’s out there, it is far more useful to know what is in your water.

Taking the time and investing a bit of money in a professional water test from a certified lab can save you from endless guesswork and save you from spending money on the wrong solutions.

If you use city water, researching water through your local municipality is a great start. Recognizing that municipalities expect consumers to use a point-of-use or whole-house filters will also help.

After all, getting a water test and the right filter will not only save you money; it will save your health and your plants.