What happened? Arsenic contamination of concern (up to 200 ug/ft2) was detected in a laboratory while investigating an abnormally high urine arsenic level in an employee working in an affiliated laboratory. The most significant contamination was on and around the analytical balance and on the floor. Other minor contamination was detected on door and drawer knobs and pulls, keyboards, phone, etc. While there are no legal surface contamination limits, some samples exceeded those recommended by a prominent national lab (PDF Format) (<139 ug/ft2, as an acceptable housekeeping dust on surfaces and <9.3 ug/ft2, as a release criteria to non-regulated areas). The laboratory was closed for decontamination by a hazard remediation contractor and reopened after repeat surface wipe sampling demonstrated adequate decontamination.
Why did it happen? The pattern of contamination appeared the result of analytical balance use and was being spread around on the floor. Presumably, the balance and surrounding areas were not decontaminated after use (a strong chemical odor and staining were noted when collecting surface wipe samples from the balance) and possibly, weighing practices prone to contamination spread were employed (a paint brush was noted on the balance, presumably to dust it off before weighing). Other minor contamination indicated poor glove use practices (i.e., using contaminated gloves to handle other objects).
How can a similar occurrence be avoided? The arsenic compounds used in the lab are highly toxic, carcinogens and therefore require Chemical Safety Level 2 (CSL-2) practices. CSL-2 practices are for carcinogens, reproductive toxins and highly toxic chemicals and address designated areas, containment, labeling and special disposal requirements.
All handling (including weighing) of these types of chemicals must be conducted in a manner that prevents contamination. Conducting weighing operations in a containment device is one option to prevent contamination (e.g., HEPA-filtered weighing hood for powders or a fume hood). Proper glove use is also important. Standard operating procedures (SOPs) must be developed and those performing these operations should be adequately trained on the SOPs. Training can include trial weighing operations and glove use using a non-hazardous color indicator dye followed by damp wiping surfaces to detect the dye. In some cases, periodic wipe sampling should be performed to monitor work practices.
All storage and work with these chemicals must be confined to posted, designated areas. All waste, containers, equipment and materials potentially contaminated with these types of compounds must be identified with appropriate warning labels. Contaminated apparatus, glassware, clothing and shoes must be thoroughly decontaminated by effective means or deposited in appropriate, labeled waste containers before being removed from the designated areas. Work surfaces potentially contaminated by these compounds must be thoroughly decontaminated by effective means before normal work is resumed in the location (i.e., dispose of removable liners as hazardous waste or HEPA-filter vacuum and/or damp wipe surfaces with soapy water).
Above – Surface wipe samples for arsenic. The sample on the right was a negative control sample taken from around an analytical balance in a lab that did not use arsenic. Other chemical contamination was evident from the staining of the wipe. Note – the contamination was not visible until moistened by the damp wipe.
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