I don't think this is going to be a problem for anyone if they flush their water system to the point where they get rid of all the red color as directed on the back of the Prestone package. That said, this stuff is not safe if consumed in large amounts and should be kept away from kids and pets and not transferred to any other container. Note it has a child resistant cap so a child seeing the pretty red color and thinking its like Kool Aid would have to work at it to get into it.
The key parts of the Prestone MSDS :
POTENTIAL HEALTH EFFECTS:
ACUTE HAZARDS
INHALATION: No significant adverse health effects are expected from
inhalation exposure.
SKIN CONTACT: No significant irritation is expected.
SKIN ABSORPTION: No adverse effects are expected due to the very low
systemic toxicity of propylene glycol.
EYE CONTACT: Direct contact may cause stinging and tearing but no
residual injury or discomfort.
INGESTION: Considered relatively non-toxic following acute ingestion,
however, lactic acidosis, stupor and seizures have been reported
following chronic ingestion and in individuals with underlying kidney
disease.
SECTION 4: FIRST AID MEASURES
INHALATION: No adverse effects are expected, however, if irritation or
other symptoms develop, remove to fresh air. Seek medical attention if
symptoms persist.
SKIN CONTACT: Remove contaminated clothing and wash skin with soap and
water. Seek medical attention if irritation develops.
EYE CONTACT: Immediately flush with water, holding open eyelids, for
15 minutes. Seek medical attention if irritation persists.
INGESTION: If swallowed, get immediate medical advice by calling a
physician, poison control center or emergency room. If advice is not
available and a significant quantity has been swallowed, give 1 or 2
glasses of water or milk and induce vomiting. Take the victim and the
product container to the nearest emergency treatment center or
hospital. Do not attempt to induce vomiting or give anything by mouth
to an unconscious person.
NOTES TO PHYSICIAN: Following acute ingestion signs of toxicity are
unlikely. Ethanol treatment as in ethylene glycol poisoning is
inappropriate. There is no specific antidote. Treatment should be
directed at the control of symptoms and the clinical condition.
Monitor for acidosis and central nervous system effects.