Occupational Exposure Assessment for Hazardous Substances in a School

The Problem

The technicians in the preparation room of chemistry department at a school had been complaining of narcotic symptoms such as headaches, nausea and drowsiness when carrying out work in the lab. The department used a large selection of chemicals, such as solvents, acids, bases and compounds. These were in a variety of forms, including salts and solutions. As well as the chemicals themselves, there was an array of laboratory equipment.

The Solution

On the day of the survey, the students were carrying out a common organic synthesis of cyclohexane from cyclohexanol. Here cyclohexanol was reacted with phosphoric acid in toluene and heated to form cyclohexane and water. This was all done on a bench in the classroom, with no control measures such as Local Exhaust Ventilation.

The staff worked longer hours than is typical for a school lab technician due to the school’s timetable. There were two technicians who worked in the preparation room, and a number of teachers each taking a class of 20 students.

The chemicals were all stored in a fume cupboard if necessary, which was in working order and recently tested. However, as shown in the picture below, the cupboard was slightly open throughout the shift.

Once the experiment was underway, there was a distinctive odour of toluene throughout the chemistry department. Even after a short period, the technicians were complaining of headaches, unfortunately, the survey was carried out in the middle of winter, so natural ventilation wasn’t possible.

However the main exposure problem occurred when dirty glassware was returned to the preparation room for cleaning. Here dirty glassware was returned on trolleys and could be left for up to an hour before being cleaned.

In spite of these poor housekeeping practices, the levels of solvent and acid fume exposure were insignificant at around 3-5% of the relevant Workplace Exposure Values. A number of recommendations were suggested as part of the occupational exposure assessment, including:

• Carry out spot checks using passive sampling methods
• Close the fume cupboard fully when access isn’t needed
• Clean dirty glassware as soon as practicable
• When symptoms occur, technicians should be allowed an extended break to allow short term symptoms to pass
• All experiments involving organic synthesis should be carried out in a fume cupboard rather than on an open bench in the laboratory

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