Can sewer gas make pets or children sick?

OSHA's fact sheet says hydrogen sulfide is heavier than air and collects in low, poorly ventilated areas. NIOSH puts its density at 1.19 times that of air. So when sewer gas seeps out of a dry floor drain or a loose toilet seal, the air near the floor tends to carry more of it than the air at an adult's nose.

The Agency for Toxic Substances and Disease Registry (ATSDR) spells out what that means for children. Its medical guidance says children exposed to the same levels as adults may get larger doses, because they have more lung surface and breathe more air for their body weight. In ATSDR's words, children "may be exposed to higher levels than adults in the same location because of their short stature and the higher levels of hydrogen sulfide found nearer to the ground." ATSDR adds that children may be slower to leave an area when exposed.

ATSDR is also honest about the gaps. It says there's very little information on health problems in children exposed to hydrogen sulfide, and exposed children probably have effects similar to adults.

The same floor-level logic applies to a dog napping by the laundry drain or a cat in a guest bathroom. Hydrogen sulfide is toxic to animals too. The lab data NIOSH used to set its danger level includes rats and mice, with lethal concentrations in the same range as the human data. There's little public data on household pets specifically, so treat a pet as you would a small child: lower to the ground and unable to tell you what it smells.

One more thing about pets. A dog that avoids a room, or a cat that stops using a litter box next to a floor drain, may be telling you about a smell before you notice it.

OSHA lists what hydrogen sulfide does as the level rises. At 2 to 5 ppm, with prolonged exposure, it may cause nausea, tearing eyes, headaches and lost sleep. Around 20 ppm, fatigue, loss of appetite, headache, irritability and dizziness. At higher levels, coughing, eye irritation and loss of smell. Wisconsin's health department adds drowsiness and nervousness.

In a child or a pet, that can look like:

• Watery, red or irritated eyes
• Coughing or harder breathing
• Unusual tiredness or drowsiness
• Upset stomach, vomiting or not eating
• Crankiness or restlessness that eases when you step outside

The pattern matters more than any one sign. If symptoms show up in one room and fade outdoors, and that room smells like sewer, take it seriously. OSHA also notes asthma patients may react at 2 to 5 ppm, so a child with asthma deserves extra caution.

### Low levels over weeks still count

A faint smell that hangs around for weeks is easy to get used to. That's the case to watch in a home with kids. OSHA's fact sheet says repeated exposure can cause health effects at levels that were once tolerated without any, and that effects of low-level exposure can show up hours or even days later. It lists eye inflammation, headache, fatigue, irritability, trouble sleeping and digestive upset from repeated or prolonged exposure. ATSDR adds that long-term exposure may be more serious for children because they have more years ahead for effects to show.

ATSDR also says hydrogen sulfide doesn't build up in the body. That is the good news. Once the leak is fixed and the air clears, the exposure stops.

### Pregnancy

Families often ask about this. ATSDR says it isn't known whether hydrogen sulfide causes birth defects in people, and studies in lab animals suggest low concentrations during pregnancy do not cause birth defects. Its medical guidance notes some evidence of a link to miscarriage risk and says there are no human studies of developmental effects. If you're pregnant and have been around a strong or lasting sewer smell, tell your doctor what you were exposed to and for how long.

### Where kids and pets meet it at home

The usual spots are low and quiet: a guest bathroom nobody uses, a laundry room floor drain, a garage drain next to the dog's bed, a basement or a playroom beside a bathroom that sits empty for weeks. In an apartment, it can be a unit next to a vacant one whose traps have dried out. Walk those spots at floor level with your nose. That's where a small child or a pet spends its time.

Fresh air comes first, then the phone calls. Don't stay behind to hunt for the source.

1. 1Take children and pets outside into fresh air. Open windows on the way out if it's quick.
2. 2Call 911 if anyone is struggling to breathe, is confused or passes out. Wisconsin says to evacuate and call the fire department if you believe the gas is concentrated in an enclosed space.
3. 3Call your doctor, pediatrician or vet for symptoms that don't clear once they're outside. Tell them it may be hydrogen sulfide from sewer gas.
4. 4Rule out natural gas. A rotten-egg smell near a stove, water heater or gas meter may be a gas leak. Leave and call 911 and Southwest Gas at 877-860-6020. See a house that smells like gas or rotten eggs.

### Two things not to do

• Don't mask it. Air fresheners, candles and plug-ins cover the smell, and the smell is the only early warning most homes have. A candle near a strong gas smell is also an ignition source.
• Don't wait for a pet or child to "tell you." A toddler can't describe a headache, and a dog can't either. If a room smells like sewer and someone small seems off, act on the smell.

A small dry trap is the most common cause and the easiest fix. Run water into every little-used drain: guest bathrooms, the laundry floor drain, a garage drain, a wet bar. If the smell comes back, something else is open, such as a vent, a toilet seal or a cracked line. Why a bathroom drain smells like sewer and what a P-trap does walk through the usual culprits.

If the house has a floor drain in a laundry room or garage that rarely sees water, make refilling it part of a routine, like changing the air filter. A trap that never dries out never lets gas through. Pay attention to rooms where kids sleep and where pets spend the day. A nursery next to an unused bathroom or a dog bed by the laundry drain is exactly where a slow leak does the most harm. For the full list of symptoms by level, see the first signs of sewer gas poisoning.

HQ Plumbing offers 24/7 emergency service and free estimates. We'll find the drain, vent or seal that's letting sewer gas into the house and close it.