Xylenes (o-Xylene, m-Xylene and p-Xylene)

Xylene

What is Xylene?

Xylenes (dimethylbenzenes) are volatile solvents widely used in chemical synthesis, consumer
Products and agricultural chemicals. Xylene exists as a mixture of three isomeric forms: i.e. ortho, meta and para isomers. Mixed xylenes are colorless flammable liquids that are practically insoluble in water and have a sweet odour (the odour threshold for m-xylene is 1.1 ppm). The chemical formula for mixed xylenes is C₈H₁₀, and the molecular weight is 106.16 g/mol.

The commercial product is a mixture of all three isomers with m-xylene predominating, usually 60-70%. The technical product, "mixed xylenes", contains approximately 40% m-xylene and 20% each of ethylbenzene, o-xylene and p-xylene. Small quantities of toluene and C9 aromatic fractions may also be present.

Chemical Formula

C₈H₁₀

Chemical Structure

Chemical Name

ortho-xylene meta-xylene para-xylene

Synonyms

Xylene is also known as dimethylbenzene, methyltoluene, xylol, ortho-xylene, meta-xylene, para-xylene and xylene (non-specific name).

What products may contain Xylene?

Mixed xylenes are used in the production of ethylbenzene, as solvents in products used in the printing, rubber and leather industries such as paints paint thinners and coatings, and are blended into petrol. It occurs naturally in petroleum and coal tar.

What are some main emission sources of Xylene?

Sources of xylene emissions to air include: petrol, motor vehicle exhaust, petroleum refineries and terminals, service stations, lawnmowers and other petrol fuelled implements. Xylenes are used in the manufacture of chemicals, polyester, paints, dyes, lacquers and wood burning stoves and fire. The uses above provide opportunity for increased xylene volatilization.

What is the airborne exposure limit for Xylene Vapour?

The Hazardous Substance Information System (HSIS) supplied by the Office of the Australian Safety and Compensation Council (ASCC) provides an eight (8) hour time weighted average (TWA) exposure limit of 80 parts per million (80ppm) and a short term exposure limit (STEL) of 150 parts per million (150ppm), to minimize sensory irritation to most workers. ASCC states that these levels should also be low enough to protect the workers from narcotic and other chronic health effects.

What is the Primary Target of Xylene and how might this affect my health?

The Primary Target Organs following Inhalation Exposure is that of the Central Nervous System (CNS) i.e. Chronic Occupational exposure to xylene has been associated with headache, EKG abnormalities, altered memory and confusion. Xylene is absorbed following oral, dermal, or inhalation exposure; can be stored in adipose tissue; and is eliminated in the urine after conjugation with glycine.

The Acute effects of exposure to xylenes include dyspnea and irritation of the nose and throat; gastrointestinal effects such as nausea, vomiting, and gastric discomfort; mild transient eye irritation; and neurological effects such as impaired short-term memory, impaired reaction time, performance decrements in numerical ability, and alterations in equilibrium and body balance. It is apparent that all isomers or mixtures of isomers produce similar effects although specific isomers may not be equally potent in producing the effects. Greater additive respiratory and neurological toxicity is shown when exposure is to a mixture of toluene and xylenes.
Hand immersion studies with m-xylene have shown transient irritation, redness, dryness, and scaling of the skin
The Chronic effects of exposure to xylenes, as seen in occupational settings, has resulted primarily in neurological effects such as headache, dizziness, fatigue, tremors, incoordination, anxiety, impaired short-term memory, and inability to concentrate. Labored breathing, impaired pulmonary function, increased heart palpitation, severe chest pain, abnormal EKG, and possible effects on the kidneys have also been reported.

The US Agency for Toxic Substances and Disease Registry (ATSDR) has calculated a chronic inhalation minimal risk level (MRL) of 0.4 mg/m3 (0.1 parts per million [ppm]) for mixed xylenes based on neurological effects in occupationally exposed workers. The MRL is an estimate of the daily human exposure to a hazardous substance that is likely to be without appreciable risk of adverse noncancer health effects over a specified duration of exposure.

The U.S. EPA (1992) has placed xylene in weight-of-evidence group D, not classifiable as to human carcinogenicity, based on no significant increases in the incidence of tumors observed in rats or mice of both sexes following oral administration of technical grade xylene.

How might I be exposed to Xylene?

Consumers are most likely to be exposed to xylenes by using consumer products containing toluene especially if there is not good ventilation, including petrol, paint, varnish, rust preventatives and cigarette smoke. Workers in the industries that use or produce xylene are at risk of exposure, these include: Painters and paint industry workers, biomedical laboratory workers, distillers of xylene, wood processing plant workers, service station and car maintenance workers, metal workers and furniture refinishers. Consumers can also be exposed to xylene by exposure to air from production and processing facilities using xylene, and automotive exhaust.

Xylene is readily absorbed after oral and inhalation administration. Several studies with humans exposed by inhalation to xylene at concentrations of 100-1300 mg/m3 have shown that approximately 60% of the xylene present in inspired air is absorbed by the lungs, regardless of the isomer or mixture used (U.S. EPA, 1985). Dermal absorption is minor following exposure to xylene vapour, representing only 1-2% of that absorbed by the lungs. However, dermal absorption may be significant if liquid xylene contacts the skin (U.S. EPA, 1985).

It has been documented that chronic occupational exposure by laboratory technicians to xylene has resulted in associated symptoms including chronic headache, chest pain, electrocardiographic abnormalities, dyspnea, cyanosis of hands, fever, leukopenia, malaise, impaired lung function, and confusion.

How can exposure to Xylene be monitored?

Biological exposure monitoring (or health surveillance) to mixed xylenes may be determined by measuring the breakdown products of mixed xylenes in the urine or by measuring levels of xylene in blood or exhaled breath.

Xylene may be determined in occupational air using collection on adsorbent tubes, solvent desorption and GC/FID analysis. Detection limits depend upon the amount of air sampled and accuracy is very good. There are commercially available badges based on passive charcoal sampling. After extraction with carbon disulfide the xylenes can be detected by gas chromatography.

For adsorbent tube samples, samples are collected using personal sampling pumps that have been calibrated, with sampling devices attached, to within ±5% at the recommended flow rate of 50 mL/min. The sampling devices consist of adsorbent tubes that are contained in commercially available tube holders. The devices are connected to the pumps with flexible, non-crimpable tubing. SKC adsorbent charcoal tubes are commonly used, they contain 100 mg of adsorbent in the front section and 50 mg in the back section.

The Assessment of the Material Safety Data Sheets (MSDS)

In many cases the first step in planning an Occupational Hygiene Program is to assess the Material Safety Data Sheets (MSDS) for all the materials used by an organization, in addition to that of the chemical under investigation, Xylene. In planning the program, GETEX hygienists must take into account any additive effects of a combination of materials, and may also take into account a different time of exposure, for example, a 10 hour working day.

GETEX can help you instigate monitoring and/or devise a site management plan to control your site’s emissions.

The staff at GETEX has many years of experience in airborne hazardous material risk assessments including many projects involving the monitoring and management of VOCs including Xylene, Toluene and Formaldehydes. GETEX are ready to recommend & implement cost-effective monitoring programs in any part of Australia and overseas. Together with the administrative assistance and monitoring GETEX can recommend appropriate engineering controls and Personal Respirable Protective Equipment.

Why Choose GETEX?

Trained Consultants with many years of experience across a broad range of occupational air quality services
Trained Consultants employed by Getex are members of Australian Institute of Occupational Hygienists, Inc (AIOH)
GETEX offers specialist occupational hygiene advice , 24 hours/7 days a week.
GETEX carries full professional indemnity insurance

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Sources of information used in preparing this webpage

National Pollutant Inventory (NPI), Department of Environment and Conservation (accessed April, 2007)
Agency for Toxic Substances and Disease Registry (1989), Public Health Statement Xylene (accessed April, 2007)
Agency for Toxic Substances and Disease Registry (2000), ToxFAQS Xylene (accessed April, 2007)
US Environmental Protection Agency and the Office of Air Quality Planning and Standards (2000), Chemical summary for Xylene (accessed April, 2007)
Australian Safety and Compensation Council (2004), Exposure Standard Xylene (accessed April, 2007).