Urine luck: an expert’s guide to biological monitoring
Marchwood
Environment
A biological sample measures the total uptake of a chemical by an individual through inhalation, ingestion, or dermally—or a combination of all three. Biological monitoring is especially useful in workplace environments where chemicals can be absorbed through the skin, and where the main control measures are PPE such as gloves and masks. Analysis of urine samples in this way helps businesses check exposure levels in their workplace to assess its overall safety, check that control measures are working, and that work practices are protective.
Biological monitoring is used to complement air analysis, which also provides data to enable businesses and occupational hygienists to keep an eye on chemical exposure levels. Often the analysis of the sample measures the substance of interest, but sometimes it is more appropriate to measure the metabolite of the substance. The metabolite is made when the substance is broken down by the body, and can include isocyanates, dichloromethane, benzene, mercury, and metals.
Read on to find out more about these metabolites, and how Marchwood can help.
Isocyanates
Isocyanates are highly reactive, low molecular weight compounds containing the isocyanate group NCO. Organic compounds containing two or more isocyanate groups are known as diisocyanates and, as they are very durable, are typically used in the manufacture of adhesives, foams, and polyurethane. They are commonly produced during certain automotive tasks, such as paint spraying, and can also be found in building insulation materials. Isocyanates have become one of the leading causes of occupational asthma and are powerful irritants to various parts of the body.
Isocyanates are analysed using GC/MS (C/I), and results are creatinine calculated so they can be directly compared with the Biological Monitoring Guidance Values (BMGV). Citric acid is used as a preservative, but if the sample isn’t being sent to the lab within 48hrs of being taken it should be frozen.
Dichloromethane (Methylene Chloride)
Dichloromethane is used in many different industries, such as in the production of pharmaceuticals and as a degreasing agent. In 2010, the European Union banned its use in paint strippers. While dichloromethane is effective in eradicating very durable coatings without damaging the substrate, such as in historical preservation and graffiti removal, breathing in the vapours may cause shortness of breath, coughing, and eye irritation. Contact with the liquid itself has also been known to cause burning sensations and pain. Great care must be taken as it is a clear, colourless volatile—so look out for its sweet odour as that (as well as analysis!) is your only clue of its presence.
Methylene chloride is analysed using GC/MS (headspace). Due to the nature of the analysis, it is important that the sample bottle is filled to the top. The sample is stable for up to 7 days refrigerated.
S-Phenyl mercapturic acid (S-PMA)
S-PMA is a highly specific metabolite and a preferred marker of benzene. Benzene represents one of the biggest chemical health hazards related to the production and refining of petroleum products. It occurs naturally in oil and gas reservoirs and follows the whole production chain. It is classified as a carcinogen and mutagen with a ‘skin notation’, indicating the possibility of significant skin absorption.
Benzene can cause serious health problems. The immediate effects of high inhalation exposure can include headaches, tiredness, nausea, and dizziness. Unconsciousness may occur if exposure is very high, while long term exposure to benzene can result in serious blood disorders such as anemia and leukemia. There is potential exposure to benzene at work from the following industries: oil refineries, chemical/petrochemical plants and offshore installations, coke works, storage, and the distribution and use of petrol.
GC/MS is used to analyse benzene. The sample is stable for up to 6 days at room temperature.
Mercury
When elemental mercury is present in the air, it poses an immediate health risk to workers exposed to it. It is poisonous in all forms and, as a non-specific toxin, attacks many of the body’s systems. At low levels of exposure, symptoms include memory loss, poor coordination, headache, visual and hearing problems, and emotional changes including mood swings, irritability, nervousness and excess shyness, insomnia, tremors, and other stress-like symptoms. At high levels, mercury exposure could result in kidney issues and respiratory failure. Businesses of occupations including offshore oil workers, dentists, healthcare staff, and laboratory workers should be particularly careful to monitor their employees’ exposure levels.
Mercury absorbed into the body is excreted slowly into urine, with its concentration reflecting cumulative exposure over the previous 2 to 4 months. Urine levels are therefore relatively constant and will accurately reflect the overall level of mercury exposure, correcting day-to-day variations in intake.
Cold Vapour Atomic Fluorescence Spectroscopy (CVAFS) is used to analyse mercury, with results creatine calculated so they can be directly compared with the BMGV. Significant consumptions of certain foods such as shellfish can increase mercury levels, and so this should be taken into consideration alongside the results.
Metals
Different metals pose individual risks to human health. In some cases, exposure causes dermal and respiratory irritation, while others could result in fertility problems. Still others are classed as carcinogens: repeated exposure to arsenic and hexavalent chromium over long periods of time, for example, can cause cancer of the lungs, liver, and skin.
There is potential exposure to metals in a number of occupations, including but not limited to welding, aerospace, automotive, battery production, chemicals, alloy production, refining, and smelting. The route of exposure could be by inhaling dust and fumes, dermally, or by ingestion.
Marchwood has recently invested in ICP/MS instrumentation for analysing metals in urine, bringing this service fully in-house. Now that the analysis is undertaken at our own labs, we can be more flexible with turnaround times than ever before. Our expert team members can take an analysis suite of metals from one urine sample if required. This is particularly useful if you are monitoring for welding fumes.
The dangerous health issues surrounding exposure to these chemicals means that analysis is crucial to help businesses safeguard employees and remain compliant. Marchwood undertakes analysis of all the substances mentioned above, and for ease when comparing exposure limits, results are creatinine corrected where required.
To make the sampling process for biological monitoring as easy and efficient as possible, Marchwood provides pre-paid return labels and bags with all sample kits. Completely free of charge, these comprise a sample pot (and preservative where required), an outer storage pot, an absorbent pad, a consent form, and a return envelope.
For more information, or to order a kit now, visit our website.