Is urinary DHBMA a biomarker of 1,3-butadiene exposure?

Urinary N-acetyl-S-(3,4-dihydroxybutyl)-L-cysteine (DHBMA) and the broader mercapturic-acid pathway are scientifically well established. Together, they link exposure to electrophilic chemicals—including 1,3-butadiene—to metabolism and urinary elimination.

Clinical and exposure-biomonitoring evidence

• DHBMA is a validated urinary biomarker of 1,3-butadiene exposure. It is a major 1,3-butadiene mercapturic-acid metabolite, accounting for >97% of reported urinary butadiene metabolites.
• In occupational studies, creatinine-adjusted urinary DHBMA correlates significantly with 8-hour time-weighted-average airborne butadiene. One analysis estimated that approximately 700 µg/L DHBMA corresponded to 0.25 ppm airborne butadiene.
• Its greatest value is for recent or post-shift exposure in settings with a characterized exposure history. For an individual—particularly at low concentrations—DHBMA cannot by itself establish the exposure source or precisely quantify dose because background excretion and tobacco-related variability occur.

Mechanism and elimination

• DHBMA is itself a mercapturic acid. Electrophilic chemicals first react with glutathione, spontaneously or via glutathione S-transferases, producing glutathione conjugates.
• Enzymatic removal of glutamate and glycine produces cysteine conjugates; subsequent N-acetylation, principally involving renal NAT8, forms the final N-acetylcysteine mercapturate.
• These metabolites are generally more polar and water-soluble than their parent electrophiles, supporting predominantly urinary excretion, with biliary elimination contributing for some compounds.

Interpretation considerations

• Urinary mercapturates reflect recent internal exposure and metabolism, but concentrations depend on collection timing, urine dilution/creatinine adjustment, renal function, transport, and metabolic differences.
• Although usually detoxifying, some cysteine conjugates can undergo β-lyase metabolism to bioactive products.

Bottom line

• The claim is supported: DHBMA is a biomarker of 1,3-butadiene exposure, and mercapturic acids are downstream glutathione-derived metabolites that facilitate elimination of electrophile-derived chemicals, mainly through urine.