Mercury poisoning

A 35-year-old man presents to the emergency department due to cough, shortness of breath, and chest pain for the past week. The patient has also been experiencing frequent nausea and vomiting since symptom onset. He started a new job at a medical instrument manufacturing company three weeks ago. Past medical history is significant for exercise-induced asthma. Family history is unremarkable. Temperature is 37.2°C (99.0°F), pulse is 80/min, respirations are 27/min, and blood pressure is 110/60 mmHg. Physical examination reveals erythema of the conjunctiva and oral mucosa. Wheezing is heard on auscultation of the lung fields. Which of the following is the most likely precipitating factor of this patient’s clinical condition?