Manganese water limits: 3 household figures explained

Start with the number on your report

Minnesota's manganese water figures are 100 micrograms/L for infants drinking tap water or formula made with it, and 300 micrograms/L for other listed households.

Key takeaways

• Confirm the report's unit before comparing your result.
• Ask everyone who makes bottles which water they use.
• Choose the household figure that matches those answers.
• Keep the report and contact your local health department if your result exceeds that figure.

A manganese result on a private well test or a community water report is one number with a unit attached. Before you can judge it, you need to know two things: which unit the lab used, and who in your home drinks the water or uses it to make food. Manganese is a naturally occurring metal found in rocks and soil. It can dissolve into groundwater, so levels can differ from one well to the next, even on neighboring lots.

This guide matches a result to the figures published by the Minnesota Department of Health (MDH). The MDH manganese page gives separate figures for infants, for households where everyone is older than one year, and for daily intake. Those figures are Minnesota's. If you live in another state, they do not automatically apply to you. Check with your state drinking water program or local health department for its own numbers, and do not mix figures from two places.

Check the unit before you compare

Lab reports usually state a unit in micrograms in each liter (micrograms/L) or milligrams in each liter (mg/L). Micrograms are much smaller than milligrams, so the two units can differ by a very large factor. The MDH figures are written in micrograms/L, so convert the lab's value to micrograms/L before you compare it. If you are unsure how to convert it, ask the lab to confirm the value in micrograms/L.

A unit mix-up is easy to make, and it changes the answer a lot. A result written in mg/L can look far smaller than it really is if you read it as micrograms/L. Write the converted value on the report next to the original, so you do not have to convert again later.

Some reports show a "less than" value. That means the amount was below what the lab could measure. It tells you the level was under the lab's limit, but it does not give you an exact number to compare. Ask the lab what that limit is so you know how much room there is.

Read the rest of the report

Reports are laid out differently by lab, but most include the same core details. Look for the name "manganese" or its symbol, Mn, the result and its unit, the date the sample was taken, and the lab's name. Some reports also list a reporting limit, which is the lowest amount the lab can measure with confidence.

Check where the sample came from, too. A sample taken from a well house or an outdoor spigot tells you about that point in the system. It may not match the water at your kitchen tap if there is a treatment unit, a storage tank, or a separate line in between.

If your report lists more than one manganese value, do not guess which one applies. Ask the lab which value reflects the water you drink. That single question prevents a lot of confusion when you compare results.

Who drinks the water matters most

The MDH figures depend on the people in your home, not only on the result. Before you read any figure, make a short list:

• Every person who lives in the home, with an age for each.
• Any infant, and whether that infant ever drinks tap water.
• Any formula, and what water is used to mix it.
• Anyone else who prepares bottles or cooks for the household, such as a relative or a caregiver who visits.

A caregiver may use a different water source than you do, so ask them directly rather than assuming. Write down the answers. You will need them when you pick a figure, and you will need them again if the routine changes.

Figure one: infants who drink tap water or formula made with tap water

If you have an infant who drinks tap water or drinks formula made with tap water, MDH says a safe level of manganese in your water is 100 micrograms/L or less. This is the lowest household figure on the page. It applies whenever an infant in your home takes in the water directly or through formula.

Formula is the detail people most often miss. Water used to mix formula counts under this figure, even if the rest of the family drinks bottled water. If the bottles are made with tap water, you are in this group, regardless of what the adults drink.

If you are not sure whether the infant ever takes in tap water, treat your home as this case until you have a clear answer.

Figure two: infants who never drink tap water or formula made with tap water

If you have an infant who never drinks tap water or formula made with tap water, MDH's figure is 300 micrograms/L or less. The word "never" carries the weight here. An answer like "usually" or "mostly" does not qualify. If bottles are sometimes made with tap water, or a caregiver fills a bottle from the kitchen tap when you are out, the infant belongs in the first group.

Keep this answer current. Recheck it when the feeding routine changes, such as when a new caregiver starts, when a family member begins helping with bottles, or when the household changes how formula is prepared. An answer that was right last month may not hold after a change in routine.

Figure three: households where everyone is over one year old

If everyone in your household is more than one year old, MDH says a safe level of manganese in your water is 300 micrograms/L or less. This figure applies to the household as a group. One person who is one year old or younger means this sentence does not cover your home, and the infant figures above apply instead.

What "safe level" means on this page

MDH uses the phrase "safe level" for each of these figures. Read it as the state's stated number for a specific group of people, not as a promise about your water. A figure tells you whether a result meets the number MDH gives for your household. It does not measure every risk in your water, and it does not replace advice from your doctor or your local health department.

The figures also depend on the exact wording. "100 micrograms/L or less" and "300 micrograms/L or less" both describe a result that is at or below the number. A result equal to the figure meets it. A result just above it does not. Keep that distinction in mind when you compare a report to the table.

Matching your result in one table

Use this table to find the figure for your home:

Start with the first row that describes your home. If an infant is in the home, only the first two rows are possible, and your answer to the formula question decides between them.

Illustrative example: the same result in different homes

Suppose your well reports an illustrative result of 300 micrograms/L. In a home where an infant drinks formula mixed with that water, the result is over the figure for that household. In a home where the infant never uses tap water and everyone else is over one year old, the same result meets the 300 micrograms/L figure. The number is the same in both homes. The answer depends on who uses the water.

Daily intake is a different question

MDH also gives daily intake figures. It says the recommended manganese intake for children over eight years old and adults varies from 1,900 to 2,600 micrograms a day. It also says that infants should consume 600 micrograms or less of manganese a day.

These daily numbers measure something different from the water figures. A water result is a concentration: how much manganese is in each liter. An intake figure is the total a person takes in over a day from every source. Water is one source. Food and other drinks also contain manganese, so a water result alone cannot tell you whether a person's total intake is above or below a daily figure.

You can still use simple arithmetic to see what water contributes. Multiply the concentration by the volume of water consumed. Compare that amount with the daily figure for that person, and remember that the rest of the day's food and drink adds to the total. If you are worried about an infant's total intake, ask your pediatrician.

What most community water already meets

MDH estimates that about 90 percent of Minnesotans using community public drinking water systems receive water with levels of manganese below 100 micrograms/L. That sentence is useful context. It tells you that the 100 micrograms/L infant figure is a level most community water already meets. It does not tell you anything about your own well, and it should not be used to judge your own result.

Private wells: testing is up to you

A community system has an operator who tests the water and reports the results. A private well is different. The owner usually decides when to test, which lab to use, and what to do about a result. That makes your own report the main information you have about your water, so keep it with its date and the lab's name. For related questions, read about private and public water supplies.

A single sample describes the water on the day it was taken. If your result is close to a figure, or the report is several years old, a retest gives you a clearer picture. Use a lab that handles drinking water samples, and follow its instructions for container, storage, and delivery time.

Old wells can change the picture

Some properties have wells that nobody remembers. The Wellowner guide on old, unused wells puts the problem simply: "The biggest problem is that old wells can be forgotten." If you bought the house recently, ask the seller about any old wells, and check with your local health or water agency.

Knowing every well on the property tells you which water you actually tested. If you sampled one well but the house is fed by another, your result belongs to the wrong source.

Talking with the people who make bottles

Matching a result is only useful if the household answers the questions honestly. Ask the people who make bottles where the water comes from, and ask again from time to time, not only once. A grandparent who watches the baby on Tuesdays may fill a bottle at a different sink. Write the matching figure on a card near the sink or on the fridge, so anyone who prepares a bottle can see it.

Retesting and when to do it

Retest when the household changes, when your result is close to a figure, or when the report is old. Retest after any work on the well or treatment equipment that you think might affect the water.

Keep a simple log

A short log makes every later decision easier. Use one page, or one note on your phone, and record four things each time you test: the date, the lab, the result with its unit, and who was living in the home at that time. Add a line whenever the household changes, such as a new baby, a new caregiver, or a visitor who regularly makes bottles. Over time, the log shows you which figure applied at each point and when you need to test again.

Keep copies of the original lab reports with the log. A handwritten number is easy to misread later, but the report shows exactly what the lab sent you. The guide to private well records to keep can help you organize the file.

When a result is close to a figure

If your number is close, retest with a lab that handles drinking water samples, and ask your local health department what the result means for your home.

Treatment and next steps

If your result is over the figure that applies to your home, treatment may be an option. The right choice depends on your water source and the full set of test results, so work with a water treatment professional who can test your water and recommend options. Be cautious of any product that claims to remove manganese without first testing your water. A claim made without a test does not tell you whether the product fits your situation. Before choosing equipment, read the home water treatment device checks.

Common mistakes

• Reading mg/L as micrograms/L, which makes the number look far smaller than it is.
• Using the 300 micrograms/L figure for an infant who drinks tap water or formula made with tap water.
• Treating "sometimes" as "never" for infant bottles.
• Using a community average as if it were a result for your own well.
• Choosing a table row without asking the caregiver who makes the bottles.

Today, put your latest report beside your household list and mark the matching table row; ask the lab about any unclear unit before comparing.

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Questions people ask

Does a result at or below 100 micrograms/L mean my baby is fine? No; meeting that MDH water figure does not answer every question about your baby's health or your water. Keep the report on file and retest when things change.

The water looks clear. Does that mean there is no manganese? No, clear water does not prove the manganese level is low. Dissolved manganese is usually not visible. Only a test can show the amount.

Can I use the 300 micrograms/L figure while I wait for a retest? Only if you are certain no infant drinks the water or uses it for formula. If there is any doubt, treat your home as the infant case until the answer is clear.

Do I need the daily intake figures? They help you think about total intake. For most households, the water figures in the table are the first step.

Next steps checklist

1. Confirm the unit and the sample date on the report.
2. List everyone in the home, their ages, and every use of the water, including formula.
3. Pick the matching row in the table above.
4. If your result is over the figure for your home, contact your local health department or state drinking water program.
5. If a baby in your home drinks tap water or formula made with it and your result is above 100 micrograms/L, talk with your pediatrician.
6. Keep the report, the lab name, and the date together, and retest when the household or the well changes.

A manganese result is easy to read once you know the unit and the household. Match the two, check the right figure, and take the next step that fits your home.