NACE in urine: A marker of acrylonitrile and smoke exposure

NACE is a urine marker that can help assess recent uptake of acrylonitrile. For many people, tobacco smoke is the most plausible major source; industrial exposure also matters in certain jobs. The result is particularly useful when assessing a specific change. It is not a test of general detoxification capacity.

NACE: A trace of acrylonitrile in urine

N-acetyl-S-(2-cyanoethyl)-L-cysteine is known as NACE and, in scientific publications, as 2CYEMA. It belongs to the mercapturic acids. After acrylonitrile enters the body, it can be conjugated with glutathione and processed further; a measurable excretion product then reaches the urine.

Acrylonitrile is a volatile compound found in tobacco smoke and certain industrial processes. Breathing it in is an important route of exposure. Skin contact may also matter at work, so describing the lungs as the only route would be too narrow.

Laboratories generally measure NACE using mass spectrometry and may report the result relative to urine creatinine. The sample mainly reflects recent exposure, rather than an amount accumulated over years. The useful measurement window depends on exposure patterns and the method; it is not a universal one- or two-day cutoff. See the US biomonitoring study of 2CYEMA.

Why acrylonitrile exposure is investigated

Smoking and secondhand smoke are important sources outside particular workplaces. Other exposure routes may be relevant in industrial settings. A measurable metabolite can help document suspected uptake biologically, rather than relying only on smell or a rough assessment of the environment.

The health relevance of the original chemical does not mean every detectable NACE result already shows an adverse effect. The concentration describes excretion. It does not directly reveal how much glutathione was used, whether the kidneys are overburdened, or whether acrylonitrile caused particular symptoms.

One measurement cannot reliably distinguish a single encounter from an ongoing source. That requires an exposure history and, where appropriate, carefully timed repeat samples. A decline after stopping smoking or improving workplace controls may fit with lower exposure. This practical question is usually more useful than looking for a universal pass-or-fail value.

Who might consider a NACE test?

Testing is especially relevant to occupational contact with acrylonitrile, including certain areas of plastics or rubber manufacturing. A targeted investigation of smoke exposure may also be appropriate. Not every job involving plastic, and not every combustion source, produces the same exposure.

People regularly exposed to secondhand smoke can discuss whether a measurement would support a concrete decision. A test is not required before avoiding smoke or quitting smoking; the benefits of those steps do not depend on an abnormal NACE result.

Reducing avoidable harmful exposures is particularly important during pregnancy and when trying to conceive. That does not establish a general recommendation for NACE screening. A single sample cannot confirm the safety of a pregnancy or predict a child’s development.

Reading a NACE result

The report often compares the measured concentration with population data. Such references describe the group studied and are not automatically thresholds for health effects. Check whether the result is given per liter of urine or per gram of creatinine.

A low value may fit with little recent uptake or sampling after the substance has been excreted. It does not demonstrate exceptional liver or kidney function. A higher value may indicate greater recent contact but does not identify the source or duration on its own.

Individual metabolism and excretion also influence the result. A high value therefore does not prove slow detoxification, and a very high single result cannot reliably distinguish an intense one-off exposure from repeated contact.

Eye or airway irritation, headaches, and neurological symptoms can occur after contact with different substances. They should not be attributed to a single marker. After a specific acute incident with significant symptoms, medical assessment takes priority over routine follow-up sampling.

What can change the result?

Recent smoke exposure and the time between contact and sampling are among the main influences. A sample after a smoke-free weekend answers a different question from one collected after an exposed work shift.

Fluid intake also matters: drinking a lot lowers the concentration per liter of urine. Adjustment for creatinine helps comparisons but does not remove every difference between people or samples. Detection limits and laboratory ranges may vary as well.

Differences in glutathione conjugation and subsequent processing are biologically possible. A single NACE number cannot determine the size of your glutathione stores or whether you need supplements.

What other information helps?

Other smoke or volatile organic compound markers may, for a suitable question, show whether several groups of substances are elevated together. They do not replace an exposure history or a focused workplace investigation.

Kidney function and liver tests can add important information when there is a medical reason to measure them. They do not need to accompany every NACE test routinely. Urine creatinine used to adjust for dilution and blood creatinine or eGFR used to assess kidney function answer different questions.

What the marker can and cannot do

NACE can indicate recent acrylonitrile uptake and support comparisons before and after a useful change. It does not reliably identify the exact location, product, or a disease. A single value also cannot calculate long-term risk.

A consistent pattern under comparable measurement conditions is more informative than a chance difference. If values fall after better protection, that is compatible with reduced exposure. It remains important to investigate the actual working or living conditions.

Frequently asked questions

What does a NACE test measure?

N-acetyl-S-(2-cyanoethyl)-L-cysteine in urine, a mercapturic acid marker used to assess acrylonitrile exposure. It measures recent exposure rather than directly measuring its health effects.

Should I have NACE tested?

It may be useful for a specific occupational or environmental question. Heavy smoke exposure or a workplace using the relevant chemical may be reasons to consider it. A test should support a decision; it is not a prerequisite for quitting smoking or improving protection.

How often should I test?

There is no general monitoring calendar. Repeat sampling depends on the suspected source and the purpose. An arbitrary interval of several months does not automatically suit a marker of recent exposure.

What affects the result?

Mainly exposure, timing, urine dilution, metabolism, and the laboratory method. A blanket list of all foods, cosmetics, or pesticides as possible sources would not be helpful; the relevant ingredients and activities matter.

How do I prepare?

Fasting is generally not required. Follow the laboratory’s instructions on first-morning or specifically timed urine collection, storage, and transport. Record smoke exposure and relevant work tasks. If a recent incident is the question, waiting several exposure-free days before sampling may miss useful information.

How reliable is the test?

Validated mass-spectrometry methods can measure the marker precisely. A good analytical method cannot compensate for poorly planned collection, however. A low value after too much time has passed may miss earlier uptake.

What does an unusual result mean?

It is a reason to review recent exposures and measurement conditions. It does not prove organ damage or impaired metabolism. Depending on the circumstances, a targeted repeat test or occupational-health assessment may follow.

How should I interpret my report?

Read the value, units, and laboratory range together with the timing and exposure history. Bring specific details about smoking, work, and symptoms to the discussion. Additional tests should answer their own clear question; a large, nonspecific panel is not automatically better.

Sources

• De Jesús VR, Zhang L, Bhandari D, Zhu W, Chang JT, Blount BC (2021). Characterization of acrylonitrile exposure in the United States based on urinary N-acetyl-S-(2-cyanoethyl)-L-cysteine (2CYEMA): NHANES 2011-2016. Journal of Exposure Science & Environmental Epidemiology, 31(2), 377-385. https://doi.org/10.1038/s41370-020-00286-1 — Source
• Pluym N, Gilch G, Scherer G, Scherer M (2015). Analysis of 18 urinary mercapturic acids by two high-throughput multiplex-LC-MS/MS methods. Analytical and Bioanalytical Chemistry, 407(18), 5463-5476. https://doi.org/10.1007/s00216-015-8719-x — 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