A lack of evidence that 2-hydroxyethylmethacrylate (HEMA) and 2-hydroxypropylmethacrylate (HPMA) cause asthma

Pemberton et al, in their 2023 review article, discussed the challenges in the classification of chemical respiratory allergens based on human data using the case studies of 2-hydroxyethylmethacrylate (HEMA) and 2-hydroxypropylmethacrylate (HPMA) as examples. The authors explained that because there was no widely accepted or formally validated tests for the identification of chemical respiratory sensitizers that there is a heavy reliance on human data from clinical examinations. They went on to explain that such investigations are critical for the diagnosis of occupational asthma, and in guiding remedial actions and are typically solely designed with that purpose in mind, As a consequence, these investigations do not reliably identify specific chemicals within the workplace that are the causative agents, highlighting several reasons for this, including the fact that specific inhalation tests conducted as part of clinical investigations are frequently performed with complex mixtures rather than single substances, that sometimes inhalation challenges are conducted at concentrations above the OEL and STEL, where effects may be confounded by irritation, and that involvement of immune mechanisms cannot be assumed from the observation of late asthmatic reactions.

In their review of the four publications containing clinical case studies implicating HEMA and/or HPMA they concluded that the clinical evidence presented in these case studies provided no firm basis for concluding that HEMA and/or HPMA were responsible for the observed respiratory effects.

Pemberton MA, Kreuzer K, Kimber I. Challenges in the classification of chemical respiratory allergens based on human data: Case studies of 2-hydroxyethylmethacrylate (HEMA) and 2-hydroxypropylmethacrylate (HPMA). Regul Toxicol Pharmacol. 2023 Jun;141:105404. Publication