20.2 Environmental Health, Lead, Poisoning & Toxicology

Environmental health and toxicology is clinical category #18. Domain I already asked you to counsel smoke-free housing, carbon monoxide detectors, and disaster kits. This section is the clinical half: which exposure you screen for, which ingestion is an emergency, and which home remedy you must stop. Water safety and drowning layers live in Chapter 4.1. Here the child has already met the toxin, the gas, the heat, or the cold.

Quick Answer: There is no safe blood lead level. CDC's blood lead reference value is 3.5 µg/dL. An esophageal button battery and two or more magnets (or a magnet plus metal) go to the ED now. For household ingestions, call Poison Control at 1-800-222-1222 and do not induce vomiting. Acetaminophen overdose is N-acetylcysteine in hospital, timed to the level — not ipecac at home.

Clinic opening. A 2-year-old is pale and constipated. The family rents a house built in 1968. They have been using an imported eye cosmetic from a relative overseas. If you treat the visit as "toddler diet" and never order a blood lead level, you missed category #18.

Lead — current CDC reference value, not last decade's number

Lead is a neurotoxin. Effects on cognition, behavior, and hearing occur well below the levels that cause anemia, abdominal pain, or encephalopathy. The exam trap is using an outdated "level of concern" of 10 µg/dL or the 2012 reference of 5 µg/dL as if those were still the action line.

As of the current CDC standard used in 2026 teaching, the blood lead reference value (BLRV) is 3.5 µg/dL. That number is a population reference (about the 97.5th percentile in young U.S. children), not a toxicology "safe threshold." No BLL is safe. A capillary result at or above 3.5 µg/dL needs a venous confirmatory sample. Do not start chelation off an unconfirmed fingerstick.

Screening. Medicaid-enrolled children are tested at 12 and 24 months (or as soon as possible by 72 months if missed). In the absence of a local risk-based plan, universal screening in that window is the conservative primary-care move. Ask the housing-year question at well visits. An elevated venous BLL triggers environmental investigation (health department), iron-and-calcium nutrition counseling, and timed repeat levels — not a chelation prescription from the well-child room. Chelation is a toxicology/hospital decision at much higher confirmed levels (classically in the range of ≥45 µg/dL), never a first move at 3.5.

Lead also sits with anemia in Chapter 19.2. This chapter's job is the source, the 3.5 µg/dL reference, and the fact that you do not wait for frank anemia before you act.

Carbon monoxide, heat, and cold

Carbon monoxide is colorless and odorless. Think winter, a storm, a generator in a garage, a charcoal grill indoors, an unvented heater, or several household members with "flu" at once — headache, nausea, sleepiness, without fever as a reliable discriminator. Cherry-red skin is a textbook extra, not a required finding. Counseling that belongs at well visits: working CO detectors on each level, especially near sleep. A suspected exposure goes to the ED for carboxyhemoglobin measurement and 100% oxygen; selected severe cases get hyperbaric oxygen. Do not send that family back to the unventilated generator.

Heat illness. Heat exhaustion is still a perfusing, usually sweating child who can drink and whose mental status is close to baseline — remove from heat, oral hydration, ED if not improving. Heat stroke is a medical emergency: CNS dysfunction (confusion, seizure, coma) with severe hyperthermia. Cool while you call EMS. Do not wait for an ice bath protocol you do not have in clinic.

Cold injury. Frostnip is pale, numb, reversible with gentle rewarming. Frostbite is frozen tissue — do not rub with snow, do not use a dry stove as the rewarming plan, and do not thaw if immediate refreeze is likely during transport. Hypothermia with altered mental status or arrhythmia risk is ED care, not a waiting-room space heater and discharge.

Time-critical ingestions: button battery, magnets, hydrocarbons, iron

Button (disk) battery in the esophagus is a tissue-injury emergency. Injury can begin in about two hours. Drooling, pain, vomiting, or a toddler who "might have swallowed a remote battery" is not a clinic serial-exam project. Do not induce vomiting. Get the child to an ED that can x-ray and remove. If the child is ≥12 months, some prehospital protocols use honey (about 10 mL every 10 minutes) only while already going to the ED and within about 12 hours of ingestion — never as a reason to stay in clinic, and never in infants under 12 months because of botulism risk. A nasal or ear disk battery is the same class of do-not-dig-in-clinic object (see 20.3).

Magnets. One small magnet that has passed into the stomach may be followed with imaging and close observation per GI protocol. Two or more magnets, or a magnet plus a metal object, can trap bowel between them and cause fistula, perforation, and necrosis. That is an ED/surgical clock, not "wait for it to pass" advice over the phone.

Hydrocarbons (lamp oil, gasoline, furniture polish, some solvents) kill by aspiration chemical pneumonitis, not by a number on a bottle. Do not induce vomiting — that is how you create the aspiration. NPO, watch the airway and oxygen, ED observation. A child who "just tastes fine" after a gulp of lamp oil can still bloom a pneumonitis over hours.

Iron. Prenatal vitamins and adult iron tablets are the classic toddler lure. After ingestion there may be GI symptoms (vomiting, diarrhea, hematemesis), a deceptive latent period, then shock, acidosis, and hepatic injury. Abdominal x-ray may show radiopaque tablets. Serious ingestions are hospital care; deferoxamine is the chelator used for severe iron poisoning — not something you start from an outpatient drawer. Call Poison Control. Do not induce vomiting.

Acetaminophen, organophosphates, pesticides — and the number you actually call

Acetaminophen is in every household. An acute pediatric ingestion around ≥150 mg/kg (some protocols use a higher threshold in older children) is enough to start the timed workup; massive ingestions and unknown time still go to the ED. The 4-hour (or later) level is plotted on the Rumack-Matthew nomogram. Antidote is N-acetylcysteine (NAC) given in hospital. Early liver enzymes can be normal — that is the trap that sends a child home. Activated charcoal may be used in the ED very early; it is not a home plan. Ipecac is not used.

Organophosphate (many agricultural insecticides) poisoning is cholinergic crisis: the DUMBBELS/SLUDGE picture — diarrhea, urination, miosis, bradycardia, bronchorrhea, emesis, lacrimation, salivation. Treatment is decontamination of clothes and skin (protect yourself), atropine for muscarinic features, and pralidoxime in hospital, not a clinic experiment. Pesticides as a class also include pyrethroids and other agents with different toxidromes — you do not need every molecule memorized; you need Poison Control and ED transfer for a symptomatic child.

Poison Control: 1-800-222-1222. Put it in the caregiver's phone at toddler well visits. You call it too. Do not crowd-source an antidote from a parenting forum. Do not induce vomiting. Do not give neutralizing acids or bases. The primary-care NP initiates the call and the transfer; toxicology runs the antidote.

Clinic close. Housing before 1978, imported cosmetics, a missing remote battery, a sibling's prenatal vitamins, a generator in the garage, or a toddler with lamp oil on the chin: name the toxin, refuse emesis, call Poison Control, and move the time-critical objects — button batteries and paired magnets — to the ED without a clinic delay.