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Propylene glycol monomethyl ether occupational exposure (PGME). 4. Analysis of 2-methoxypropionic acid in urine
Anne Devanthéry1, Michèle Berode, Pierre-Olivier Droz
1Institute of Occupational Health Sciences, Bugnon 19, 1005 Lausanne, Switzerland. Anne.Devanthery@inst.hospvd.ch
Objective:
The two isomers propylene glycol monomethyl ether [PGME-alpha (1-methoxy-2-propanol, M2P) and PGME-beta (2-methoxy-1-propanol)] have different toxicities due to the different ways they are metabolised. The higher toxicity of PGME-beta has been attributed to the formation of 2-methoxypropionic acid (2-MPA) as a metabolite of primary alcohol. Six healthy male volunteers were exposed to PGME-alpha vapour (15, 50 and 95 ppm) with and without respiratory protection for 6 h, including a 30-min break. They were also exposed to PGME-alpha liquid (10% or 30% in water), via one hand, for 30 min or 1 h. Commercial products of M2P always contain a small quantity of the beta isomer, and GC analysis has shown that the product used for this human volunteer exposure contained approximately 0.3% of the beta isomer. The objective of this study was to determine the levels of 2-MPA in urine after these exposures to 99.7% PGME-alpha.
Method:
An analytical method developed by Laitinen [6] was used for the determination of 2-MPA in the urine of exposed volunteers.
Results:
End exposure levels of 2-MPA were found to reach from 1.19 to 3.29 mg/l for inhalation and dermal exposure to PGME-alpha vapour and from under the detection limit to 2.10 mg/l for exposure of one hand in PGME-alpha liquid. 2-MPA concentrations in urine samples from a non-exposed person or from a person exposed to PGME-alpha vapour at 15 ppm (inhalation and dermal exposure) and also from a person exposed to PGME-alpha vapour up to 95 ppm with respiratory protection (dermal-only exposure) all varied from under the detection limit to 0.30 mg/l and are then not significant.
Insights
Exposure to propylene glycol monomethyl ether (PGME-alpha) can lead to detectable levels of 2-methoxypropionic acid (2-MPA) in urine. Even low-level exposure to PGME-alpha, especially with respiratory protection, resulted in insignificant 2-MPA levels, suggesting a low risk.
Area of Science:
- Occupational Health
- Toxicology
- Analytical Chemistry
Background:
- Propylene glycol monomethyl ether (PGME) exists as two isomers, PGME-alpha and PGME-beta, with differing toxicities.
- PGME-beta's higher toxicity is linked to its metabolism into 2-methoxypropionic acid (2-MPA).
- Commercial PGME-alpha contains trace amounts of PGME-beta, necessitating investigation into 2-MPA formation.
Purpose of the Study:
- To quantify 2-MPA levels in urine following controlled exposure to high-purity PGME-alpha.
- To assess the impact of inhalation and dermal exposure routes on 2-MPA metabolite levels.
- To evaluate the significance of 2-MPA detection under various exposure scenarios, including respiratory protection.
Main Methods:
- Utilized a validated analytical method (Laitinen et al.) for 2-MPA determination in urine.
- Exposed healthy male volunteers to PGME-alpha via inhalation (15, 50, 95 ppm) and dermal (10%, 30% solutions) routes.
- Collected urine samples post-exposure for precise metabolite quantification.
Main Results:
- Inhalation and dermal exposure to PGME-alpha vapor resulted in urinary 2-MPA levels ranging from 1.19 to 3.29 mg/l.
- Dermal exposure to PGME-alpha liquid yielded 2-MPA levels from below detection limit to 2.10 mg/l.
- Exposure to 15 ppm PGME-alpha vapor and higher concentrations with respiratory protection showed insignificant 2-MPA levels (under 0.30 mg/l).
Conclusions:
- Exposure to PGME-alpha can lead to measurable 2-MPA in urine, particularly via inhalation and direct skin contact.
- The use of respiratory protection significantly reduces 2-MPA levels, even at higher PGME-alpha concentrations.
- Low-level PGME-alpha exposure, especially with protective measures, results in 2-MPA concentrations not considered significant from a toxicological standpoint.