Is phosphoric acid a strong acid?
 

The strength of an acid refers to its ability or tendency to lose a proton. Weaker acids have a smaller Ka than strong acids. Phosphoric acid is mediate strong acid.

hazards of phosphoric acid

When a mist of phosphoric acid is generated, mists will cause irritation of the nose, throat and respiratory tract. If eye is hurted by phosphoric acid, it may cause redness, tearing, pain, eyelid spasms, blurred vision and permanent damage. Phosphoric acid can accuse the mucous membranes of the mouth and oesophagus, leading to difficulty in dysphagia and immediate pain. Other symptoms of phosphoric acid poisoning include coughing, a sour acrid taste, nausea, vomiting, difficult breathing, conjunctivitis, severe gastrointestinal irritation, bloody diarrhoea, severe abdominal pains, extreme thirst, convulsion, shock and even death through choking (asphyxia). 

Concentrated phosphoric acid can cause a build-up of fluid in the lungs which may result in death. It can cause circulatory collapse with clammy skin, weak and rapid pulse, shallow respiration and scanty urine. Long-term skin exposure to the liquid may cause dermatitis. Repeated exposure to phosphoric acid can cause bronchitis with cough, phlegm and/or shortness of breath. People at special risk of exposure to phosphoric acid include those with chronic pulmonary disease or skin disease.