LAUSR

Dear Editor Dimethyl sulfate (DMS) is an oily, colorless liquid with a slight onion odor. Eyes, skins and respiratory tract can be injured after DMS exposure [1]. We report 16 patients exposed to DMS in a chemical leakage incident in China. Fifteen male and one female patient aged from 19 to 57 years old were admitted to our hospital on 7 July 2017. They were workers of the sorting line of a courier company. When they picked up a broken plastic bucket and transferred it to a special warehouse by an assembly line at about 10pm, two workers (Case 1 and Case 2 in the Table 1) were sprinkled on the lower extremities by the leaking liquid. They felt skin irritation and burning pain 3h later, and large amounts of blisters appeared (see Figure 1). Other 14 workers who worked at the same line reported smelling distinctive odor consistent with being exposed to the vapor. The workers complained of photophobia, lacrimation and eyes tingling after exposure for 3–10h, and developed pharyngalgia, dry cough, hoarseness and chest tightness. They continued to work till next morning and went to hospital about 13h later. Physical examination revealed blepharospasm, conjunctival congestion, pharynx congestion and edema. Corneal punctuate or patchy lesions were observed by fluorescein staining in 12 patients. The patient (Case 16 in the Table 1) who had the longest period of exposure had more serious effects; he showed coarse respiratory sounds and moist rales at the bottom of the left lung. Arterial blood gas analyses (ABG) showed his PaO2 being decreased to 62mmHg (nasal catheter oxygen inhalation 2 4L/min). Laryngoscopy revealed congestion of his bilateral vocal cord and pharyngeal mucosa. Chest X-ray showed an increased lung texture with reticular shadows in both lungs, and a patch of hazy shadow in the left lower lung. Chest X-ray of other patients showed clear texture in nine cases and increased lung markings in four cases. All patients were admitted for observation, and had their contaminated clothing removed and the burned skins and eyes irrigated with saline promptly. Oxygen inhalation through nasal catheter and ultrasonic spray inhalation with dexamethasone and gentamicin was administered. According to the manifestations, chest X-ray and ABG, all patients were intravenously dripped with dexamethasone 10–40mg/d for 3–7 days. Symptomatic treatments for relieving bronchospasm, and systemic as well as local antimicrobial therapy were also administered. All cases fully recovered and were discharged after 5–30 days. The incident was a consequence of the courier sender who transported the hazardous chemicals illegally. He admitted that the liquid was DMS. The accident scene was blocked by the police; unfortunately toxic substances in the workshop were not tested. The chemical composition of the liquid was determined by the solid-liquid mass spectrometer. It was confirmed that the main composition was dimethyl sulfate; a small amount of iodoethane, potassium iodate and chromyl chloride were also found. Dimethyl sulfate can be hydrolyzed to produce sulfuric acid, methyl sulfate and methanol, leading to irritation and even corrosive effects of eyes and respiratory tract after exposure. In our cases, the symptoms were delayed for several hours after the exposure, the reason of which might be the time needed for the hydrolysis of DMS. Skin burns would occur in direct contact areas, but one of previously reported cases suffered perineal injury despite the lack of direct contact [2]. Mucous injuries generally occurred first in the eyes and then progressed to upper airway [3]. The manifestations