Phenylglyoxylic acid in urine: a marker of solvent exposure

Phenylglyoxylic acid in urine can indicate recent contact with styrene or ethylbenzene. Often called PGO or PGA, the marker is used particularly in occupational health. It helps assess exposure, but cannot identify the source product or establish health damage on its own.

A breakdown product of styrene and ethylbenzene

Styrene and ethylbenzene are aromatic compounds. Relevant exposures can occur during certain resin and fiberglass work, in industrial processes, and through exhaust fumes or tobacco smoke. The specific product matters: not every resin or plastic contains the same volatile parent compounds.

Breathing contaminated air is an important route of uptake. Skin contact and, depending on the circumstances, ingestion can contribute too. The body processes the parent compounds through oxidative pathways, producing metabolites including mandelic acid and phenylglyoxylic acid that can be measured in urine.

Laboratories often test PGO alongside mandelic acid. A sample mainly reflects the preceding hours to roughly one or two days, depending on exposure and sampling conditions. It is not a guaranteed detection window or a measurement of a total dose accumulated over months. Analytical methods and occupational use.

At relevant exposure levels, the parent substances can affect the nervous system and irritate the eyes or airways. Headache, dizziness and slower reactions are possible but nonspecific symptoms. PGO is an exposure marker, not a direct test of nervous-system or liver function.

Why the marker can be useful

Working with a styrene-containing resin in a poorly ventilated space provides a concrete reason to investigate uptake. An appropriately timed sample can contribute to that assessment. Check the safety data sheet to establish whether an epoxy or another resin contains styrene; do not infer it from the general product name.

Symptoms that recur during the same task and improve on days off are important clues. A PGO result can contribute to the overall assessment, but does not prove the cause of symptoms. Several substances and other stresses are often involved.

Comparable repeat measurements can help assess changes after protective measures are improved. Better extraction ventilation or a different suitable product may reduce uptake. A single low result after time away from work, however, says little about exposure during a typical shift.

Discuss relevant solvent contact with occupational health early if you are pregnant or planning pregnancy. This is not a general recommendation to measure PGO in every pregnancy. The main question remains whether there is a specific exposure and how to avoid or control it.

Reading a PGO result

Laboratory reports may give an unadjusted concentration or a creatinine-adjusted value. Creatinine adjustment accounts for some urine-dilution differences. It improves comparability, but does not replace consistent sampling plans.

For occupational questions, the protocol may call for a sample at the end of a shift or workweek. A morning sample is therefore not always best. The substance, work schedule and agreed protocol determine the timing.

A low result is consistent with little recent uptake or collection after excretion. It does not rule out earlier contact and is not a comprehensive statement about pregnancy safety or nerve function.

A higher result may indicate greater recent contact. It does not establish liver or kidney damage or a specific cause of symptoms. Repeatedly unusual results may be a reason to review the workplace, ventilation, products and protective measures more closely.

The type of comparison range also matters. Population data describe measurements in a group; occupational assessment values address a different question. Do not transfer a range from one report to another without checking its units, method and purpose.

What can change the measurement?

Time since contact, urine dilution, smoking, other chemicals and individual metabolism affect the result. The balance between mandelic acid and PGO can change too. One concentration cannot diagnose “poor detoxification.”

Experience with this marker is particularly extensive in occupational settings. Applying it to very low everyday exposures requires care because exposure levels and surrounding conditions differ. In a US population study, smokers had higher median urinary PGA than nonusers, supporting tobacco smoke as an important source. Population data on styrene and ethylbenzene.

For follow-up, use the same laboratory where possible, similar collection conditions and comparable timing relative to work. Notes covering the preceding day or two can help explain apparently contradictory results.

What PGO answers, and what remains uncertain

The test can indicate recent uptake of relevant parent compounds. On its own, it cannot reliably distinguish styrene from ethylbenzene or identify the product or location responsible. It cannot calculate long-term disease risk either.

Mandelic acid and other carefully selected information can improve interpretation. General liver, kidney or inflammation tests should have their own medical indication. A large stack of laboratory results cannot replace a description of the actual work involved.

Repeatedly elevated measurements or symptoms after solvent contact justify occupational or environmental health advice. Significant acute symptoms need prompt assessment regardless of any planned urine test.

Frequently asked questions

What is a PGO test?

It measures phenylglyoxylic acid in urine. This metabolite can form when the body processes styrene and ethylbenzene, and is often used alongside mandelic acid to assess recent exposure.

Should I get tested?

Testing may be useful when there is a specific suspected contact, such as certain resin work, with symptoms that fit the timing. Routine screening without a clear reason is generally less useful. Product information helps determine the appropriate test.

How often is testing needed?

There is no universal schedule. Repeat measurements may help during continuing exposure or after changes in protection. They should use comparable conditions and answer a specific question.

What affects the result?

The main influences are exposure intensity, time before collection, urine dilution, other chemicals and individual metabolism. Proper storage and laboratory methods also matter. One result does not prove impaired organ function.

How should I prepare?

Fasting is usually unnecessary. Follow the agreed sampling time; occupational monitoring may deliberately use an end-of-shift sample. Drink normally and record relevant tasks. Do not delay necessary protective measures for the sake of testing.

How accurate is the test?

Validated methods can measure PGO reliably. Its medical meaning also depends on suitable collection planning. An accurate measurement from a sample collected too late cannot reliably reconstruct earlier exposure.

What does a result outside the range mean?

It is a reason to review possible sources and sampling conditions. A high number does not independently diagnose poisoning, and a low number does not establish especially efficient elimination. The next step depends on the whole situation.

How should I interpret my report?

Use the complete report, including units, reference range and any creatinine adjustment. Add safety data sheets, work times and symptoms. This helps the professional advising you decide whether better exposure control, a targeted repeat sample or further medical assessment is needed.

Sources

• Chua SC, Lee BL, Liau LS, Ong CN (1993). Determination of mandelic acid and phenylglyoxylic acid in the urine and its use in monitoring of styrene exposure. Journal of Analytical Toxicology, 17(3), 129-132. https://doi.org/10.1093/jat/17.3.129 — Source
• Capella KM, Roland K, Geldner N, Rey deCastro B, De Jesús VR, van Bemmel D, Blount BC (2019). Ethylbenzene and styrene exposure in the United States based on urinary mandelic acid and phenylglyoxylic acid: NHANES 2005-2006 and 2011-2012. Environmental Research, 171, 101-110. https://doi.org/10.1016/j.envres.2019.01.018 — Source
• Calafat AM, Needham LL (2008). Factors affecting the evaluation of biomonitoring data for human exposure assessment. International Journal of Andrology, 31(2), 139-143. https://doi.org/10.1111/j.1365-2605.2007.00826.x — Source
• Barr DB, Wilder LC, Caudill SP, Gonzalez AJ, Needham LL, Pirkle JL (2005). Urinary creatinine concentrations in the U.S. population: Implications for urinary biologic monitoring measurements. Environmental Health Perspectives, 113(2), 192-200. https://doi.org/10.1289/ehp.7337 — Source
• Centers for Disease Control and Prevention. (2021). Fourth national report on human exposure to environmental chemicals, updated tables, March 2021. https://stacks.cdc.gov/view/cdc/105345 — Source