Is Your Lawn Fertilizer Safe for Kids? What the Research Says

My dad called me last week and told me he just put Milorganite on his lawn. The same lawn my kids play on every time we visit. I told him I'd look into it. What I found changed how I think about lawn care entirely.

Most parents research what goes into their kids' food, their water, their sunscreen. But the lawn? Nobody thinks about the lawn. Your kids roll around on it. They sit on it barefoot. They pick dandelions and put them near their faces. Whatever is on that grass is on your kids.

Here's what I found when I looked into the most common lawn fertilizers and weed killers.

What Is Milorganite, Actually?

Milorganite 6-4-0 is a fertilizer made from heat-dried microbes that have been used to treat sewage at the Milwaukee Metropolitan Sewerage District. The name stands for Milwaukee Organic Nitrogen. It has been sold since 1926 and is one of the most popular organic-labeled fertilizers in the country.

The "organic" in Milorganite's name refers to the fact that nutrients come from a biological source (microorganisms that digested human waste), not from synthetic chemicals. But that biological source is the issue.

When wastewater flows into a treatment plant, those microbes absorb and concentrate whatever is in the water. Pharmaceuticals. Industrial chemicals. Heavy metals. And increasingly, PFAS - the "forever chemicals" that are now found in virtually every municipal water supply.

The PFAS Problem with Biosolid Fertilizers

In January 2025, the Sierra Club and Ecology Center published a report called "Sludge in the Garden" that tested biosolid-based fertilizers sold to consumers. The findings were significant:

• Every biosolid fertilizer tested contained PFAS. Not some. All of them.
• Products contained between 14 and 20 different detectable PFAS compounds.
• PFOS (one of the most studied and concerning PFAS chemicals) was detected in multiple products at levels above Maine's 5.2 parts-per-billion screening guideline for biosolids.
• PFAS do not break down in the environment. Once they are in your soil, they stay there.

This is the core problem with any fertilizer made from sewage sludge. The treatment process concentrates whatever contaminants were in the wastewater. PFAS from nonstick cookware, stain-resistant fabrics, food packaging, and industrial waste all flow into municipal wastewater. The biosolids capture and concentrate them.

Heavy Metals in Milorganite

Milorganite publishes its own testing data on heavy metals. Their results show measurable levels of arsenic, cadmium, lead, and mercury. These are below the EPA Part 503 ceiling concentrations, which is what Milorganite points to as evidence of safety.

Two things to consider about that:

• The EPA Part 503 limits were set in 1993 and have not been updated. Thirty years of research on low-dose heavy metal exposure, especially in children, has happened since then.
• The limits are based on agricultural land application, not residential lawns where children play with direct skin contact and hand-to-mouth behavior.

This does not mean one application will harm your child. It means that the safety standards were not designed with a three-year-old rolling around on treated grass in mind.

Why Children Are More Vulnerable

Adults walk across a fertilized lawn in shoes and move on. Children interact with lawns differently:

• Direct skin contact. Bare feet, bare legs, lying face-down on the grass.
• Hand-to-mouth behavior. Children under five put their hands in their mouths constantly. Whatever is on the grass goes from hands to mouth.
• Higher intake per body weight. A 30-pound toddler absorbs proportionally more of any chemical than a 180-pound adult.
• Developing systems. Children's organs, immune systems, and nervous systems are still developing, making them more susceptible to chemical exposure.
• Lower to the ground. Children breathe air closer to the ground where dust and particles from treated lawns are more concentrated.

Common Lawn Products Compared

I looked at the most popular lawn fertilizers and weed killers and scored them based on what's in them and how they interact with the people who use the lawn - especially kids.

Want an instant lookup for any lawn or garden product? I added these to the Score & Swap tool. Search "Milorganite," "Scotts," or "Roundup" and get the verdict with a safer swap in seconds.

Safer Alternatives That Actually Work

The good news is that plant-based organic fertilizers are widely available, cost about the same as Milorganite, and perform well. They use feather meal, bone meal, and composted plant material instead of sewage sludge. No PFAS. No heavy metal concerns. No synthetic chemicals.

What About Weed Control?

Roundup (glyphosate) is the most commonly used weed killer in the country. The International Agency for Research on Cancer classified glyphosate as Group 2A - "probably carcinogenic to humans" in 2015. Bayer (which acquired Monsanto) has paid billions in legal settlements related to cancer claims from Roundup users.

If your kids play on the lawn, here are alternatives that do not involve glyphosate:

• Horticultural vinegar (20% acetic acid) kills weeds on contact. It breaks down quickly and does not persist in soil. Green Gobbler makes an OMRI-listed version.
• Corn gluten meal works as a natural pre-emergent. It prevents weed seeds from germinating without affecting existing plants.
• Manual removal with a stand-up weeder is the most chemical-free option. A good stand-up weeder costs about $30 and works for years.
• Boiling water kills weeds in cracks and along walkways. Free and completely chemical-free.

Note: Horticultural vinegar (20% concentration) is much stronger than kitchen vinegar (5%). It is not selective - it will kill any plant it touches, including grass. Use it on driveways, walkways, and garden beds, not on the lawn itself.

Practical Steps for a Kid-Safe Lawn

You do not need a perfect lawn to have a safe one. Here is what I recommend:

1. Switch to organic fertilizer. Replace Milorganite, Scotts, or any synthetic fertilizer with Espoma, Safer Brand, or Dr. Earth. Roughly the same cost, no PFAS or synthetic chemical concerns.
2. Water it in before the kids play. Even with organic fertilizer, water the lawn thoroughly after application. Wait 24 hours before letting kids play on it.
3. Skip the weed killer on the lawn. Accept a few dandelions. If weeds really bother you, use vinegar-based spot treatment on driveways and walkways only.
4. Take shoes off at the door. This prevents tracking lawn chemicals (from your yard or anyone else's) through the house.
5. Test your soil first. A $15 soil test from your local extension office tells you exactly what your lawn needs. Many people over-fertilize, which wastes money and adds unnecessary chemicals.
6. Consider clover. White clover fixes nitrogen from the air, so it fertilizes itself. A clover-and-grass lawn needs less fertilizer, less water, and stays green longer in drought.

The Bottom Line

Milorganite is made from treated sewage sludge, and independent testing has found PFAS in every biosolid fertilizer tested. The EPA safety limits for biosolid application were set in 1993 and were designed for agricultural fields, not residential lawns where children play.

Plant-based organic fertilizers from Espoma, Safer Brand, and Dr. Earth cost about the same and perform well. They use feather meal and bone meal instead of human waste. No PFAS. No heavy metal concerns.

One swap. Same price. Done.

If you want to check any other lawn or garden product, I added a Lawn & Garden category to the Score & Swap tool. Type in the product name and get an instant verdict with a safer alternative.