Chapter 6: Safe Handling of Chemicals
This chapter discusses the major routes of exposure to chemical substances during laboratory work, and several safe handling practices that can minimize your risk while working with chemical substances. The last section lists practices for the safe use of hydrofluoric acid.
Do not confuse acute and chronic exposure with acute and chronic effects. Acute exposures to chemicals are for short periods. Chronic health effects can develop from acute exposures depending on the properties and amount of the chemical. Acute or chronic adverse health effects can also occur with chronic (repeated) exposure to chemicals, even at low concentrations.
Although inhalation hazards are more often associated with gases and volatile chemicals, both solids and non-volatile liquids can also present an inhalation hazard for laboratory personnel. Laboratory chemicals in the form of dusts and particulates can become airborne when transferred from one container to another. Grinding and crushing procedures can also produce aerosols. Splashes created from spills and vigorous shaking and mixing form aerosols. Many of these generated particulates do not settle out but remain suspended in the air and travel along air currents in the room. Some of these particulates can be inhaled and deposit in the respiratory tract. For many operations, you might not recognize that aerosols are present and a hazardous situation exists. All laboratory operations involving an open vessel will result in aerosol release. Such operations include weighing, stirring, pouring, pipetting, injections with a needle and syringe, handling animals, and removing caps and stoppers. As an alert laboratory person, take care not to create aerosols.
In laboratories where toxic materials are used, do not eat, drink, smoke, chew gum, apply cosmetics, or store utensils, food, and food containers, unless your laboratory has an authorized and clearly marked food item area. Refer to the food policy in Chapter 3. In some laboratories, it might not be possible to establish a food item area due to the lack of adequate containment of volatile or toxic substances. If your laboratory has a food item area, make sure no chemicals, procedures, or laboratory equipment end up in the area. Remove gloves or other personal protective equipment that could introduce contamination to the food item area. Consider posting a reminder or labeling equipment.
Use mechanical pipetting aids for all pipetting procedures. NEVER MOUTH PIPETTE.
Also, avoid rapid mixing of liquids with pipettes by alternate suction and expulsion, or forcibly expelling material from a pipette. Take extra care when discarding contaminated gloves or plastic-backed absorbent paper used to cover the work surface, to avoid aerosolizing contaminants. Clean floors with a wet mop or with a vacuum cleaner equipped with a HEPA filter, as dry sweeping or dry mopping contaminated laboratory floors could aerosolize contamination.
Pain associated with skin exposure to HF may not occur for 1-24 hours. Unless you can rapidly neutralize the HF and bind the fluoride ions, tissue destruction may continue for days and result in limb loss or death. HF is similar to other acids in that the initial extent of burn depends on the concentration, temperature, and duration of contact with the acid. Eye exposure to concentrations of HF greater than 0.5% can result in severe ocular damage, with delayed signs and symptoms.
Hydrofluoric acid vapors are also hazardous. Ocular irritation and injury can occur from working with HF outside a vented enclosure (laboratory hood). Inhalation can cause severe throat irritation, cough, dyspnea, cyanosis, lung injury and pulmonary edema. In severe exposure cases, these can result in death.
- An adult patient who developed 25% total body surface area second degree burns after exposure to a 70% hydrofluoric acid preparation died in cardiac arrest. Ionized serum calcium level was 1.7 milligrams per deciliter (mg/dL) immediately premortem. The normal range is 4 to 4.8 mg/dL.
- A dermal exposure to 70% hydrofluoric acid over a 2.5% total body surface area resulted in death. The serum calcium level was 2.2 mg/dL.
- Two workers died following a splash exposure of 70% hydrofluoric acid to the face, chest, arms and legs. Both workers were promptly removed from site of exposure. Clothing was removed and burns were initially treated at the workplace with a cold shower and alcohol applied to burn areas. No suitable protective clothing was worn at the workplace.
- A woman died from severe chemical burns of the skin and lungs, with intense pulmonary hemorrhagic edema after having acid thrown onto her face during an attack.
- A patient with HF burns over 8% of his body died from intractable cardiac arrhythmia secondary to the depletion of ionized calcium.
- Familiarize yourself with the hazards specific to HF before handling. Consult this Chapter, the SDS, the EHS HF webpage and label information.
- Always handle HF in a properly functioning laboratory hood, and in an area equipped with an eyewash and safety shower.
- Do not work alone when using HF and alert colleagues when using the material.
- Ensure that calcium gluconate antidote is on hand before handling HF.
- Required Personal Protective Equipment:
- Face shield (plastic)
- Gloves: Thin disposable gloves (such as 4, 6, or 8 mil blue nitrile gloves) used in laboratory operations provide a contact barrier only and should be disposed immediately when contamination is suspected. Thicker (10-20 mil) PVC or neoprene gloves provide better resistance to HF but do not provide the necessary dexterity for many lab procedures. Thinner PVC or poly gloves can provide some resistance to HF, but require immediate changing at the first sign of contamination. Do not wear disposable gloves without double gloving because of the potential for exposure through pinholes
- Acid resistant apron
- Long pants and sleeves (note that these are required when working with all corrosive materials, including HF)
- Closed toe shoes (required for ALL laboratory work)
In the event of a skin or eye exposure to HF:
- Have someone call 911 immediately, to facilitate arrival of medical assistance.
- Remove all exposed clothing and immediately wash all exposed areas with copious amounts of water from the safety shower or eyewash. Flush exposed eyes for at least 15 minutes, but flush exposed skin for only five minutes, followed by treatment with a calcium source.
- For skin exposures, after flushing for five minutes, apply a gel or slurry of calcium gluconate (preferred) or calcium carbonate directly to the exposed area. Use concentrations between 2.5% and 33%.
- For severe exposure cases, consider subcutaneous infiltration with calcium gluconate. Infiltrate each square centimeter of affected dermis and subcutaneous tissue with about 0.5 mL of 10% calcium gluconate, using a 30-gauge needle. Repeat as needed to control pain. Split or remove nails to treat nail bed burns. The earlier this is administered, the more rapidly symptoms resolve.
- CAUTION: Avoid administering large volumes of subcutaneous calcium gluconate, as this will result in decreased tissue perfusion and potential necrosis.
Note that calcium gluconate gel has an expiration date. Make sure that you always have access to a non-expired supply if you are working with HF.
DO NOT USE CALCIUM CHLORIDE – Calcium chloride is irritating to the tissues and may cause injury.
Store HF and HF waste in a cool, dry place away from incompatible materials. Storage areas should be clearly marked as containing HF. HF reacts with many materials; therefore, avoid contact with glass, concrete, metals, water, other acids, oxidizers, reducers, alkalis, combustibles, organics and ceramics. Store in containers made of polyethylene or fluorocarbon plastic, lead, or platinum. Place storage bottles in polyethylene secondary containment trays.
Never store HF, or HF waste, in glass containers.
Use 3M’s Universal Sorbent or similar, as it does not react with HF. Do not use spill sorbents that contain silicon, such as vermiculite or sand, as this can produce silicon tetrafluoride, an odorless toxic gas.
If the spill is large, in a confined space, or in an area where there is not adequate ventilation, evacuate the room and immediately report the spill to 911. Contact EHS at 919-962-5507 if you have questions about spill response, or if you do not feel comfortable trying to clean up the spill yourself.