Hydrogen Chloride

Mischance, legally an accident, provided the opportunity to investigate associations between an environmental exposure to hydrochloric acid (HCl) fumes and adverse health effects. A leaking container (Baker-Hughes) truck spread over 800 liters (200 gallons) of HCl onto the ground and into the air adjoining a mobile home park in Louisiana in August 1993. The investigating officer and several residents became acutely ill with burning and tearing eyes and throats, headache, chest pain, shortness of breath and flu-like complaints. Persistence and worsening of these symptoms led to a study of all of the available exposed subjects 20 months later.

Forty-five exposed adult subjects and a cohort comparison group of 56 adults had neurobehavioral testing including balance, reaction time, blink reflex latency and spirometry. They also completed health questionnaires and a profile of mood states (POMS).

These adults (exposed and unexposed) did not differ in mean age but the exposed had completed 1.2 fewer years of school (educational attainment, p<0.002). Data were analyzed by comparing means by analysis of variance and by covariance analysis. The exposed differed significantly from unexposed for balance tested with eyes open and eyes closed, simple and two choice visual reaction, digit symbol and for placing pegs in a pegboard in women only. Scores on POMS and all 6 components were also significantly different. Balance sway speeds greater than the mean value for unexposed subjects were associated with proximity to the HCl leak as were induced mid-flow rates (FEF25-75 and FEV1). The most exposed subject, the proband of the study had further functional deterioration 5 months after initial testing. Within a year he developed serious impairment of his gait and balance, a sharp decrease in memory, weakness of his left side and headaches and loss of the ability to concentrate. Similar memory loss, headaches and respiratory illnesses in another law officer and people in the downwind zone from this release led to the investigation described.

Chronic neurobehavioral dysfunction and airways obstruction occurred after environmental HCl exposure adding these effects to those on the lungs, cornea and teeth reported previously in workers. Widespread use of HCl makes a repetition of this incident probable so that safer methods of transporting HCl are clearly indicated.

Widespread use of hydrochloride acid (HCI) and other acids led to the Alkali Act in Britain to register production and to regulate releases to protect the public. Erosion of the teeth of workers by HCI fumes which was quite different from cavities was an early adverse effect of HCl but damage to airways and the lung leading to aspiration necrosis and pneumonia were well known early in this century. They paralleled in time the discovery that HCl was a principal digestive agent in the stomach. Asthma and pulmonary edema from acid inhalation have been described repeatedly in the 19th and 20th Centuries.