Reactive airways dysfunction syndrome after hydrofluoric acid inhalation

Dear Editor,

A 44-year-old man who had been working in a glass washing factory visited our hospital with cough, sputum, and dyspnea after accidental exposure to hydrofluoric acid of 50% concentration 10 days ago.

He was ex-smoker who quit smoking 10 years ago and had 5 pack years smoking history. He had usually been working in the glass washing factory in position of office based job. At this time he was exposed to 50% concentration of HF during opening of cap of HF bottle. After opening for approximately 1–2 min, he experienced a burning sensation in his eyes, nose, and mouth and he developed chest tightness and dyspnea. He had persistent problems on breathing for previous 10 days, and he finally came to hospital.

His initial blood pressure was 130/70 mmHg, pulse rate 70/min, respiratory rate 20/min, and body temperature 36.8 °C. There were no abnormal findings in physical examinations. Chest radiography and PNS waters view showed normal findings. White blood cell count was 9590 cells/μL (neutrophil, 65.1%; lymphocyte, 24.5%; monocyte, 8.6%; eosinophil, 1.5%) and other laboratory measurements were within normal ranges. Measuring bronchodilator response with pulmonary function test was done; FEV1/FVC 89%; FVC 5.10L (101%); FEV1 4.56L (121%). He showed positive reaction to ''Dermatophagoides farinae'' and ''Dermatophagoides pteronyssinus'' on allergen skin prick test. A non-specific bronchial challenge test with methacholine was performed to evaluate airway hyperresponsiveness and the result was positive (PC20 = 7.78 mg/ml).

HF (hydrofluoric acid) is a weak acid and is colorless, potent respiratory irritant with an unpleasant odor.<sup>[[#bib1|1]] and [[#bib2|2]]</sup> The boiling point of anhydrous HF is 19.5 °C and it is miscible with water, and HF fumes strongly in moist air.[[#bib2|<sup>2</sup>]] The odor threshold is reported to be 0.5–3.0 parts per million.[[#bib2|<sup>2</sup>]] HF is a toxic substance used widely in both industrial and domestic settings, and is used to produce a variety of chemicals and in numerous industrial processes.<sup>[[#bib1|1]] and [[#bib2|2]]</sup> It is most largely used in production of fluorocarbon compounds.[[#bib2|<sup>2</sup>]] HF is unique among acids because its toxicity is mostly attributed to an anion and fluoride, not to a cation and a hydrogen ion responsible for toxicity in many other acids.[[#bib2|<sup>2</sup>]] Most acids cause burns and necrosis from liberated hydrogen ions. Generally, HF is produced by the reaction of sulfuric acid with calcium fluoride.[[#bib2|<sup>2</sup>]]

HF is strong irritant to eyes, nose, throat, and skin. HF causes variable symptoms tears, eye redness, rhinorrhea, sore throat, cough, headache, and dermatalgia.<sup>[[#bib1|1]], [[#bib3|3]] and [[#bib4|4]]</sup> Even in cases in which no symptoms are present for 1–2 days after exposure, fever, cough, dyspnea, cyanosis, and pulmonary edema may occur later.[[#bib1|<sup>1</sup>]] There are few reports of adverse health effects from inhalation exposure to a consumer product containing HF. One report described a single case of chemical pneumonitis and adult respiratory distress syndrome following household use of an HF-containing rust stain remover. Another reported a case of adult-onset asthma immediately following use of the same household rust stain remover.[[#bib4|<sup>4</sup>]]

Reactive airways dysfunction syndrome (RADS), or irritant induced asthma without latency, is characterized by the immediate onset of asthma following a single exposure (or possibly several exposures) to irritating vapor, fume, or smoke.<sup>[[#bib5|5]], [[#bib6|6]] and [[#bib7|7]]</sup>

RADS was originally described by Brooks and Lockers[[#bib5|<sup>5</sup>]] in 1981 as sudden onset of non-immunological asthma resulting from an exposure to high-level irritant gases. Many cases occurred after the 9/11 collapse of the New York World Trade Center, resulting from the inhalation of fumes and particulate matters.[[#bib8|<sup>8</sup>]] Symptoms persist for at least 12 weeks but there is no previously documented evidence of asthma or other chronic lung disease.[[#bib8|<sup>8</sup>]]

According to ACCP[[#bib9|<sup>9</sup>]] RADS can be diagnosed by following conditions: (1) A documented absence of preceding respiratory complaints; (2) Onset of symptoms after a single exposure incident; (3) Exposure to very high concentrations of a mixture of sodium hypochlorite and hydrochloric acid; (4) Onset of symptoms within 24 h after the exposure, with persistence of symptoms for at least 12 weeks; (5) Symptoms simulating asthma with cough, wheeze, and dyspnea; (6) Presence of airflow obstruction; and (7) Absence of all other pulmonary diseases. RADS is also a subcategory of irritant-induced occupational asthma (OA), and irritant-induced OA can be classified by exposure concentration and duration of exposure.<sup>[[#bib8|8]] and [[#bib10|10]]</sup> RADS is characterized by extremely high exposure concentration which is over occupational exposure limit and the duration of exposure is below one day.<sup>[[#bib8|8]] and [[#bib10|10]]</sup>

The patient described in this report developed adult onset asthma based on his history of symptoms, dyspnea improvement with inhaled steroid medication, and the positive tests for non-specific bronchial hyperreactivity. His asthma had immediate onset following the exposure of high concentration of HF, and the symptoms had persisted for at least 3 months. Therefore, based on the history and medical findings he appears to be suitable for the criteria for RADS. In conclusion, we report a 44-year old man with RADS including bronchial asthma with cough, sputum, and dyspnea after exposure to high concentration of hydrofluoric acid. He was educated from avoiding exposure of HF, and now well controlled treated with normal lung function by step downing inhaled steroids.

==Conflict of interest==

The authors have no conflict of interest to declare.

==Acknowledgements==

This study was supported by Soonchunhyang University Research Fund.

==References==

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