Formaldehyde is one again coming under the spotlight, with converted shipping containers in the Northern Territory that were used for offices being found contaminated by formaldehyde and a call from CFMEU union for bans on its use. They claim formaldehyde “formaldehyde is as dangerous as asbestos” and that “union workers have reported a range of detrimental health effects from short-term exposure including asthma, breathing difficulties, skin irritations, severe excema and dizziness”. They also note that “American studies have shown a serious cancer risk associated with the substance“.
Much of the regulatory framework for formaldehyde derives form the ACGIH Documentation of Threshold Limit Values and Biological Exposure Indices. The recommendations of the ACGIH end up as a list of Threshold Limit Values or TLV’s that are often adopted by various counties as exposure limits. As published, they are designed as guidance for experts, but when enshrined in legislation tend to become more black and white, particularly when used for prosecutions.
The controversy over formaldehyde has lead the ACGIH documentation on formaldehyde to be one of the longest – at 26 pages, of all TLV Documentations. It has also lead to a lot of expense and angst for the ACGIH as it has to defend in court a number of times its health-based recommendations from both industry and individuals who think the recommendation is either too low or too high.
Over the years, the TLV has evolved-
- 1946–1947: MAC–TWA, 10 ppm
- 1948–1962: TLV–TWA, 5 ppm
- 1963–1971: TLV–CEILING, 5 ppm
- 1970: Proposed TLV–CEILING, 2 ppm
- 1972–1984: TLV–CEILING, 2 ppm
- 1981: Proposed TLV–TWA, none; A2, Suspected Human Carcinogen
- 1982: Proposed TLV–CEILING, 1 ppm; A2 Carcinogen
- 1983: Proposed TLV–TWA, 1 ppm; TLV–STEL, 2 ppm; A2 Carcinogen
- 1985–1991: TLV–TWA, 1 ppm; TLV–STEL, 2 ppm; A2 Carcinogen
- 1989: Proposed TLV–CEILING, 0.3 ppm; A2 Carcinogen
- 1992–present: TLV–CEILING, 0.3 ppm; A2 Carcinogen
- 1999: Proposed SEN (sensitizer)
- 2000: TLV–CEILING, 0.3 ppm; SEN (sensitizer); A2 Carcinogen
The two notable changes were the classification of formaldehyde as a suspect human carcinogen, based on experiments with lab rats and the Ceiling Limit to avoid it irritant effects, which effectively lowers the average or TWA exposure limit by a factor of three.
I find my eyes get irritated around 0.1 ppm and the ceiling TLV is 0.3 ppm is three times this value, so it has good warning properties.
My experience with formaldehyde has been varied so I will select three cases that may be of interest:
The lab (see my keynote paper paper at the 1998 AIOH Conference)
I was asked to investigate problems with formaldehyde in a laboratory. The formaldehyde was said to come from work on the air-conditioning system and the smell came and went. The people working in the lab complained of eye and throat irritation. The problem persisted but several sets of measurements with a Lion Formaldemeter gave low readings. For six months I kept trying to solve the problem, but then I noticed a wall heater turn or and off with a thermostat. The lab was a HPLC lab and I then realised that the waste methanol from the HPLC was evaporating and oxidising to formaldehyde on the heater. Measurements of methanol with stain tubes showed the levels to be excessive, but below the threshold of smell. The eye and throat irritancy could be also attributed to the methanol. The Lion Formaldemeter has a 5% cross sensitivity to methanol so gave falsely high formaldehyde readings, conformed with stain tube measurements for formaldehyde. The actual formaldehyde levels were shown to be well below the exposure limit but above the smell threshold. Once this was understood, the hidden methanol problem could be solved.
2. Path Lab
I was asked to give expert evidence for a pathology lab worker with respiratory problems arising from her exposure to formaldehyde. part of her job was to fill specimen jars with formalin. The lab was a converted house and still had carpet and no chemical handling facilities. I worked with the lady to set up my lab the same as the path lab, paying particular attention to the type and size of vessels and funnels and heights.
One thing I looked at before I did any measurements was the pattern of airflow when the formalin and formaldehyde laden air was displaced from a small bottle when it was filled with a funnel from a 2.5L glass Winchester. This air flow was visualised by filling the receiving bottle with smoke from a Drager smoke- tube. The smoky air jetted out of the gap between the lip of the bottle and the funnel and was directed in a narrow fan by the funnel, straight into the face of the lady. Simple Breathing Zone measurements on the lapel would grossly under-estimate the exposure.
A Bruel and Kjaer (now Innova) 1302 photo-acoustic analyser was used to measure the formaldehyde levels at her face. As the sensors in the instrument are microphones, the instrument has a huge dynamic range and keeps it calibration well, just like a sound level meter. Its a beautiful instrument and excellent for IAQ investigations.
Perhaps a salutary lesson in sometimes going back to basics rather than always following the rule book and performing Breathing Zone measurements.
3. Teaching lab
Yet another lab. A large teaching lab was built from server large demountable buildings, but the building was unusable because of the high level of formaldehyde. It transpired that the building was lined with plywood, and cheap plywood was used to win the tender. Less quality control is needed to produce strong urea formaldehyde glues if the glue is made fairly acidic, but moisture in the air can hydrolyse the glue, causing significant amounts of formaldehyde to be evolved. I has a look at the surface of the plywood with electron microscopy (a nice thing about working in a research institution was the access to nice analytic toys). The surface of the plywood was covered with a lacquered, patterned paper, but the surface mad microscopic pores. We tried to neutralise the formaldehyde with a sodium sulphite (I think) solution, but it didn’t work very well.
Its a pity that more hygienists don’t report their failures.
