Hazard Watch: Colophony in the workplace

Colophony, more commonly known as Rosin, is used across a wide range of industries and is a workplace hazard that all employers and employees should be aware of. Inhaling colophony based fumes can lead to a variety of health hazards. 

What is Colophony

Colophony is a substance produced from the sap of coniferous trees (pines, junipers, firs, cedar, etc). It’s produced when the naturally occurring liquid resins obtained from these trees and plants are heated to vaporise their volatile terpene constituents. The result is a brittle, translucent material, golden-brown in colour, that melts at temperatures above 100ºC.

It is also an ingredient in waxes, varnishes, printing ink, adhesives and soaps. One of the more interesting uses of rosin, is for applying onto string instruments like violins, cellos and double basses. It creates friction that allows the bow to grip the strings and makes them vibrate more clearly, producing a more audible sound.

Colophony is comprised of a complex mixture of resin acids (approximately 90%) and other neutral substances including diterpene alcohols, aldehydes, and hydrocarbons (about 10%).


How can Colophony be dangerous in the workplace

Colophony has several commercial applications but is mainly used as soldering flux. Soldering flux is a cleaning agent used during the soldering process of electronic components. It facilitates better soldering by cleaning and removing oxides and impurities, ensuring a permanently bonded connection. During soldering, the colophony-based solder flux is heated, and fumes containing rosin acid particulates are produced. Inhaling these fumes can lead to a variety of health hazards, including:

  • Occupational Asthma – symptoms that include coughing, wheezing and shortness of breath.
  • Allergic hypersensitivity - this can develop after several months of prolonged exposure and continue to build up to cause breathing difficulties.
  • Other symptoms of inhalation include chest pain, headaches, dizziness and in extreme cases chronic bronchitis.

Direct contact of colophony with skin can also be known to cause allergic contact dermatitis (ACD).

Monitoring exposure to colophony

The Health and Safety Executive document, EH40, sets out the workplace exposure limits for rosin-based solder flux fume. This is stated as 0.05 mg.m-3 for long term exposure (8-hour TWA reference period) and 0.15 mg.m-3 for short term exposure (15-minute reference period).

COSHH (Control of Substances Hazardous to Health) regulations require employers to identify hazards, assess the health risks caused by solder fume, and take action to prevent exposure. Control measures must then be regularly reviewed. Exposure monitoring is the most effective way to verify that control measures are working, and any current exposure levels are below those cited in the COSHH regulations.

If COSHH is not properly managed, employees are at risk of exposure. Improper assessments can lead to a loss in productivity, due to illness. This can also leave employers liable to enforcement action including prosecution under the COSHH regulations.

RPS offer the required media and subsequent analysis to measure the time weighted average concentration of colophony-based solder flux fume in the workplace. This is done by drawing air through nitrocellulose filters and analysing the resin acid components collected on the filter via gas chromatography – mass spectrometry. The team in our Manchester laboratory are highly experienced to provide clients with technical advice and support regarding colophony-based solder flux fume sampling and analysis.

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