Specific Chemical Handling and Storage

Storage Rules for Flammable Liquids

General Information:

According to the National Fire Protection Association NFPA 30: “Flammable and Combustible Liquids Code”, which applies to office, educational, and institutional occupancies and day care centers storage shall be limited to that required for the operation of office equipment, maintenance, demonstration and laboratory work.

These four rules for indoor storage of flammable and combustible liquids in Educational and Institutional Occupancies have been established by the National Fire Protection Association (NFPA):

  • Containers of Class I liquids that are stored outside of an inside liquid storage area shall not exceed a capacity of 5 L (1.3 gallons)Exception: Safety can shall be permitted up to a l0 L (2.6 gallon) capacity.
  • The combined volume of Class I and Class II liquids stored in a single fire area outside of a storage cabinet or an inside storage area not stored in safety cans shall not exceed 38 L (10 gallons)
  • The combined volume of Class I and Class II liquids stored in a single fire area in safety cans outside of an inside liquid storage area of storage cabinet shall not exceed 95 L (25 gallons)
  • The volume of Class IIIA liquids stored outside of an inside liquid storage area or storage cabinet shall not exceed 230 L (60 gallons)

Storage for industrial and education laboratory work shall comply with NFPA 45, “Standard on Fire Protection for Laboratories Using Chemicals.”

Chemical Refrigerators:

Ordinary domestic refrigerators and freezers must not be used for storing flammable liquids due to exposure to electrical components (light bulbs, switches, contacts and motors) that can become potential ignition sources. These ignition sources may initiate a fire or an explosion if flammable vapors are present. Refrigerators and freezers for storing flammable liquids and/or temperature sensitive chemicals such as peroxides or epoxies must be designed, constructed and approved for that purpose. Domestic refrigerator/freezers as well as units that have been modified to remove spark sources are not acceptable.

  • Refrigerators must be labeled on the exterior:
    • CAUTION – FOR CHEMICAL STORAGE ONLY; DO NOT STORE FOOD OR BEVERAGES IN THIS REFRIGERATOR.

    Labels may be fabricated by users provided the labels are legible and securely affixed to the refrigerator.

  • Refrigerators used to store research materials should have a comprehensive real time inventory list of the research items posted on the exterior of the refrigerator.
  • Refrigerators used for food storage in or near work areas (shops and labs) must be labeled with words to the effect of:
    • NOTICE – FOOD MAY BE STORED IN THIS REFRIGERATOR. DO NOT STORE CHEMICALS.

    Refrigerators used for food and beverage storage that are located in lunch rooms and office buildings, where there is no shop or laboratory type chemical use, do not require any postings.

Flammability Classifications for Commonly Used Chemicals:

Class IA Class IB Class IC
Dimethyl Sulfide Acetone Ethylene Glycol Diethyl Ether
Ethylene Oxide Acrylonitrile Ethylene Glycol Isopropyl Ether
Ethyl Mercaptan Ethyl Acetate Hydrazine
Hydrogen Cyanide Ethyl Alcohol (Ethanol) High Flash V.M.&P. Naphtha
Pentane Ethylene Dichloride Paraldehyde
Petroleum Ether* Ethyl Ether Styrene
Propylene Oxide Heptane Xylenes
Vinyl Chloride Hexane Butyl Alcohol
Acetaldehyde Isopropanol Butyl Aceylate
2-Butyne (Methyl Alcohol) Methanol M-Xylene
2-Chloropropane Methyl Ethyl Ketone O-Xylene
Dichlorosilane Methyl Isobutyl Ketone P-Xylene
Methyl Ethel Ether Methyl Methacrylate Amyl Alacohol
Methyl Formate Petroleum Ether* Amyl Bromide
Methyl Mercaptan V.M.&P Naphtha Butyl Nitrate
Cimethyl Sulfide Pyridine Chlorobenzene
Ethyl Amine Tetrahydrofuran Cumene
Ethyl Chloride Toluene Cyclohexanone
Ethyl Nitrite p-Dioxane Dibutyl Ether
Furan Ethyl Nitrate Hexylamine
Hydrocyanic Acid Methyl Isobutyl Ketone Isoamyl Acetate
Isoprene Methyl Methacrylate Isobutyl Alcohol
1, 3 Pentadiene Octane Nitromethane
Trichlorosilane Triethylamine Turpentine

* May fall into Class IA or IB, depending on the Boiling Point of the mixture

Source: Fire Protection Guide to Hazardous Materials, 10th edition, NFPA, 1991.

Each petroleum product (oil, antifreeze, WD40, etc.) should be categorized and kept under these limits. Some simpler rules of thumb may be easier to remember and follow:

  • Class I liquids shall not be handled or used in basements.
  • No flammable liquid storage in mechanical rooms.
  • No more than one drum of combustible liquids in one room (one drum of oil or one drum of antifreeze).
  • Minimize the amount and time that paint is stored in mechanical rooms, unless stored in flammable storage cabinets.

Flammable and Combustible Liquids*

*As defined by the National Fire Protection Association Code

For the purpose of this code, any material that has a fluidity greater than that of 300 penetration asphalt when tested in accordance with ASTM D5-97 Test for Penetration for Bituminous Materials. When not otherwise identified, the term liquid shall mean both flammable and combustible liquids.

Combustible Liquid. A liquid having a flashpoint at or above 100 degrees F. (37.8 degrees C).

Combustible liquids shall be subdivided as follows:

  • Class II liquids shall include those having flashpoints at or above 100 degrees F (37.8 degrees C) and below 140 degrees F (60 degrees C).
  • Class IIIA liquids shall include those having flashpoints at or above 140 degrees F (60 degrees C) and below 200 degrees F (93 degrees C).
  • Class IIIB liquids shall include those having flashpoints at or above 200 degrees F (93 degrees C).

Flammable Liquid. A liquid having a flashpoint below 100 degrees F (37.8 degrees C) and having a vapor pressure not exceeding 40 psia (2,068 mm Hg) at 100 degrees F (37.8 degrees C) shall be known as a Class I liquid.

Class I liquids shall be subdivided as follows:

  • Class IA shall include those having flashpoints below 73 degrees F (22.8 degrees C) and having a boiling point below 100 degrees F (37.8 degrees C).
  • Class IB shall include those having flashpoints below 73 degrees F (22.8 degrees C) and having a boiling point at or above 100 degrees F (37.8 degrees C).
  • Class IC shall include those having flashpoints at or above 73 degrees F (22.8 degrees C) and below 100 degrees F (37.8 degrees C).

Specific Chemical Information

Wisconsin Ban on Mercury-Containing Products

The State of Wisconsin has placed a ban on the sale of certain mercury –containing products. In other words, you will no longer be able to buy the following items containing mercury without an exemption.

mercury switches

thermometers

manometers

barometers

mercury-added thermostats

esophageal dilators

bougie tubes

gastrointestinal tube

flowmeters

hydrometers

hygrometers

psychrometers

pyrometers

sphygmomanometer

Mercury salts and other compounds are not banned for sale to University of Wisconsin campuses. For more details about the 2009 Wisconsin Act 44 and other information about the mercury ban and exemptions, see UW System’s publication.

Additional Resources:

Combustible Metals

Type D

List of Combustible Metals or Metal Compounds:

If your laboratory contains combustible metals or combustible metal compounds, you will need to have a type D fire extinguisher.

In the event of a fire, types A, B, and C fire extinguishing agents will react with combustible metals. Therefore, unique agents such as potassium and sodium are used in type D fire extinguishers to put out fires with combustible metals.

Type D fire extinguishers are yellow and have a five pointed star on them. The following is a list of combustible metals that require a type D fire extinguisher:

aluminum phosphide
aluminum (powder)
beryllium (powder)
calcium
calcium carbide
cerium
cesium
gallium arsenide
gallium phosphide
lithium
lithium aluminum deuteride
lithium aluminum hydride
lithium aluminum hydride bis(tetrahydrofuran)
lithium amide
lithium borohydride
lithium-6 deuteride
lithium hydride
lithium tetraphenylborate tris(1,2-dimethoxyethane)
lithium tri-tert-butoxyaluminohydride
lutetium
magnesium hydride
magnesium and magnesium alloys
neodymium
nickel catalyst (Raney)
phosphorus
phosphorus pentasulfide
potassium
potassium hydride
potassium-sodium alloys
Red-Al
rubidium
sodium
sodium aluminum hydride
sodium bis(2-methoxyethoxy)aluminum hydride in toluene
sodium borohydride
sodium borohydride cobalt-doped
sodium borohydride on alumina
sodium hydride
strontium
titanium (powder)
zinc phosphide
zinc (powder)
zirconium (powder)

Corrosive Chemical Storage

Corrosive chemicals because of their nature, prevalence in the laboratory, and variety of concentrations, constitute a series of hazards ranging from poisoning, burning and gassing, through explosion. Serious injury can result from exposure to strong acids or caustics in either the liquid, solid, or gaseous states. Corrosive chemicals in a science laboratory are usually strong acids and/or bases. Laboratory employees handling strong corrosives should always wear proper eye- and skin-protective clothing and equipment (Wear acid-proof aprons, gloves and face shields when handling highly corrosive materials such as strong mineral acids or alkyl hydroxides).

Employees should also be informed of the dangers of tissue contact with corrosives. Should there be contact between corrosives and any body tissue, particularly the eyes, immediately flush the area of contact with cool water for fifteen (15) minutes. Remove all affected clothing and immediately seek medical assistance.

Below are some guidelines for proper storage of some common corrosive materials, such as:

    • Ammonium Hydroxide — Ammonium hydroxide is a base, or caustic chemical which should be kept separate from all acids. All acids are generally incompatible with bases. Ammonium Hydroxide does not substantially attack steel, painted steel or wood, so no special cabinet is needed for it.

 

    • Acetic Acid and Picric Acid — are organic acids and should be kept separate from the inorganic, or mineral acids, such as Phosphoric Acid, Hydrochloric Acid, Nitric Acid, Sulfuric Acid, and (especially) Perchloric Acid. Acetic Acid is also combustible and more appropriately stored in a flammable storage cabinet.

 

    • Phosphoric Acid*

 

    • Hydrochloric Acid*

 

    • Nitric Acid

 

    • Sulfuric Acid*

 

    • Perchloric Acid*

 

*The mineral acids, Phosphoric Acid, Hydrochloric Acid, Nitric Acid, Sulfuric Acid, and Perchloric Acid can all be stored in a cabinet designed for Corrosive Acids.

 

SciMatCo and Justrite are examples of manufacturers that make non-metallic cabinets for these types of acids. Both brands are available from laboratory supply and safety supply companies. Some of the important design features of corrosive cabinets include:

  • no internal metallic parts
  • acid resistant coating
  • cabinet floor constructed to be able to contain spillage.

You may also want to specify cabinet vents if you intend to connect the cabinet to an external exhaust.

Concentrated mineral acids can be very reactive, even with each other. Concentrated acids can even react vigorously with dilute solutions of the same acid, if mixed together rapidly. For example: concentrated sulfuric acid mixed quickly with 1 molar sulfuric acid will generate a lot of heat. Different acids should be stored apart. If stored within the same cabinet, plastic trays, tubs or buckets work well to keep different acids apart within the cabinet.

Acids can only be used where an emergency eyewash is located within the immediate vicinity. Strict adherence to safety goggle use procedures is necessary when using acids and bases. All occupants of rooms where corrosives are used must be familiar with the Material Safety Data Sheets (MSDSs) for those materials.

Finally, you should attempt to minimize the amount of acid stored to the smallest amount practical:

  • Picric Acid and Perchloric Acid volumes should always be kept at an absolute minimum.
  • Picric Acid can form explosive salts with many metals, or by itself when dry.
  • Perchloric Acid is an extremely powerful oxidizer and must be kept away from all organic materials, including wood.
  • Perchloric Acid, if heated, must be used in a specially designed Perchloric Acid washdown fume hood, that can’t be used for anything else.

In summary, you may need one or more acid resistant cabinets, depending on the volume you intend to store. Nonmetallic cabinet(s) are recommended in addition to some other means to further isolate the different acids within the cabinet(s). Ammonium Hydroxide should be stored away from the other acids. Acetic Acid and Picric Acid should be stored in a flammable storage cabinet. The amounts of acid stored should be minimized, especially for Picric Acid and Perchloric Acid. All precautions listed on the MSDS should be understood and followed.

For further information on chemical safety, contact your professor, supervisor, principal investigator or the Department of University Safety and Assurances.

Formaldehyde and Formalin Solutions

Formaldehyde (HCHO) and formalin solutions are commonly found in the chemical and biological laboratory, principally for specimen preservation and tissue perfusion.

Long-term exposure to low levels of formaldehyde may cause respiratory difficulty, eczema, and sensitization. Formaldehyde causes irritation of the eyes, nose, throat, respiratory system; lacrimation (discharge of tears); cough; wheezing; and dermatitis. Formaldehyde is classified as a potential human carcinogen and has been linked to nasal and lung cancer, and with possible links to brain cancer and leukemia. Formaldehyde exposure is most common through gas-phase inhalation. However, it can also occur through liquid-phase skin absorption.

This OSHA Formaldehyde Standard (29 CFR 1910.1048) became effective for all laboratories on September 2, 1988. There were other phase-in dates for engineering and work practice controls; medical removal protection; hazard communication and training. UWM is subject to the OSHA standard per Department of Safety and Professional Services Chapter 332.

The standard applies to all occupational exposures to formaldehyde, i.e. from formaldehyde gas, its solutions, and materials that release formaldehyde at UWM. The standard includes requirements for:

  • exposure monitoring;
  • engineering controls and work practices;
  • respiratory and PPE protection;
  • hygiene protection and emergency preparedness;
  • medical surveillance monitoring;
  • hazard communication, labeling and training; and
  • record keeping

Exposure Monitoring:

The standard requires UWM to assure that no employee is exposed to an airborne concentration of formaldehyde which exceeds 0.75 parts formaldehyde per million parts of air (0.75 ppm) as an 8-hour TWA. UWM must also assure that no employee is exposed to an airborne concentration of formaldehyde which exceeds two parts formaldehyde per million parts of air (2 ppm) as a 15-minute short term exposure level (STEL).

The standard requires that UWM monitor employees to determine their exposure to formaldehyde. The exception: Where UWM documents, using objective data, that the presence of formaldehyde or formaldehyde-releasing products in the workplace cannot result in airborne concentrations of formaldehyde that would cause any employee to be exposed at or above the action level or the STEL under foreseeable conditions of use, UWM will not be required to measure employee exposure to formaldehyde. Examples of activities which may result in exposure levels of concern include solution formulation, specimen preservation, tissue perfusion and chemical hazardous waste operations.

The initial monitoring process shall be repeated each time there is a change in production, equipment, process, personnel, or control measures which may result in new or additional exposure to formaldehyde. OSHA specifies repeat monitoring if the exposure exceeded either the Action Level or the STEL.

Occupational Hygienic Limits (2001) for Formaldehyde:

OSHA PEL-TWA (8-hour): 0.75 ppm
OSHA STEL (15 minute exposure): 2 ppm
OSHA Action Level: 0.5 ppm 8 hour-TWA

NIOSH REL (8-hour): 0.016 ppm
NIOSH Ceiling (15 minute exposure): 0.1 ppm
IDLH: 20 ppm

ACGIH STEL: 0.3 ppm

Other: ACGIH Sensitizer and ACGIH A2 Carcinogen (suspected human carcinogen); National Toxicology Program (NTP) suspect human carcinogen; International Agency for Research on Cancer (IARC) Group 2A (probably carcinogenic to humans)

Odor Threshold: varies, odor may not be detectable at the PEL/TLV. Olfactory fatigue may occur.

Engineering Controls and Work Practices:

The standard requires UWM to institute engineering and work practice controls to reduce and maintain employee exposures to formaldehyde at or below the TWA and the STEL. The exception: Whenever UWM has established that feasible engineering and work practice controls cannot reduce employee exposure to or below either of the PELs, UWM shall apply these controls to reduce employee exposures to the extent feasible and shall supplement them with respirators which satisfy this standard.

Hygiene Protection and Emergency Preparedness:

All contact of the eyes and skin with liquids containing 1 percent or more formaldehyde shall be prevented by the use of chemical protective clothing made of material impervious to formaldehyde and the use of other personal protective equipment, such as goggles and face shields, as appropriate to the operation.

Contact with irritating or sensitizing materials (read formaldehyde) shall be prevented to the extent necessary to eliminate the hazard.

Medical Surveillance Monitoring:

The standard requires medical surveillance programs for all employees exposed to formaldehyde at concentrations at or exceeding the action level (read 0.5 ppm 8-hour TWA) or exceeding the STEL (read 2 ppm).

Hazard Communication, Labeling and Training:

Containers of formaldehyde solutions or specimens must include on the label: respiratory sensitizer, and shall contain the words “Potential Cancer Hazard.”

The standard requires that UWM develop, implement, and maintain at the workplace, a written hazard communication program for formaldehyde exposures in the workplace, which at a minimum describes how the requirements specified in this paragraph for labels and other forms of warning and material safety data sheets, and paragraph (n) for employee information and training, will be met. In the absence of specific written policies, departments shall follow the requirements of this document.

The standard requires UWM to ensure all employees who are assigned to workplaces where there is exposure to formaldehyde participate in a training program, except that where the employer can show, using objective data, that employees are not exposed to formaldehyde at or above 0.1 ppm, the employer is not required to provide training.

OSHA Hazard Communication Requirements Specific to Formaldehyde Include:

    • UWM shall provide such information and training to employees at the time of initial assignment, and whenever a new exposure to formaldehyde is introduced into the work area. The training shall be repeated at least annually.

 

    • Training shall include a description of the potential health hazards associated with exposure to formaldehyde and a description of the signs and symptoms of exposure to formaldehyde.

 

    • Training shall include a discussion of the contents of this regulation and the contents of the Material Safety Data Sheet (MSDS). Specific health hazards that the employer shall address are: cancer hazard, irritation and sensitization of the skin and respiratory system, eye and throat irritation, and acute toxicity.

 

    • Training shall include the purpose for and a description of the medical surveillance program required by this standard, including instructions to immediately report to the employer the development of any adverse signs or symptoms that the employee suspects is attributable to formaldehyde exposure.

 

    • Training shall include a description of operations in the work area where formaldehyde is present and an explanation of the safe work practices appropriate for limiting exposure to formaldehyde in each job.

 

    • Training shall include the purpose for, proper use of, and limitations of personal protective clothing and equipment.

 

    • Training shall include instructions for the handling of spills, emergencies, and clean-up procedures at UWM.

 

    • Training shall include an explanation of the importance of engineering and work practice controls for employee protection and any necessary instruction in the use of these controls. This includes function and proper use of the laboratory chemical fume hood.

 

    • Training shall include a review of emergency procedures including the specific duties or assignments of each UWM employee in the event of an emergency.

 

    • All training materials shall be available in writing and made available to the employee. In the absence of specific training documents, departments shall follow the requirements of this document and other applicable laboratory policies, procedures and good lab practices.

 

Recordkeeping Requirements:

The standard requires that UWM obtain exposure measurements for potential formaldehyde exposure. UWM shall establish and maintain an accurate record of all measurements taken to monitor employee exposure to formaldehyde.

Monitoring records shall include: the date of measurement; the operation being monitored; the methods of sampling and analysis and evidence of their accuracy and precision; the number, durations, time, and results of samples taken; the types of protective devices worn; and the names, job classifications, social security numbers, and exposure estimates of the employees whose exposures are represented by the actual monitoring results. Where UWM has determined that no monitoring is required under this standard, the employer shall maintain a record of the objective data relied upon to support the determination that no employee is exposed to formaldehyde at or above the action level.

Exposure records and determinations shall be kept for at least 30 years. Medical records shall be kept for the duration of employment plus 30 years. The Department of University Safety and Assurances maintains occupational exposure records at UWM.

Respiratory Protection:

Employees required to wear a respirator shall be included in the UWM Respiratory Protection Program. There are specific respiratory protection requirements for formaldehyde exposure, including routine change-out of cartridges and the type of respirator that must be worn.

References:

For further information on chemical safety, contact your professor, supervisor or principal investigator.

Hydrofluoric Acid Safety

Hydrofluoric Acid Information

Hydrofluoric Acid (HF) is one of the strongest and most corrosive acids known. Therefore, special safety precautions are necessary when using this chemical. HF is used in a variety of applications including glass etching, pickling of stainless steel, removal of sand and scale from foundry castings and as a laboratory reagent. Anyone using HF should implement the following safety measures. Most importantly, do not assume that dilute solutions do not require special precautions!

    1. Read the Material Safety Data Sheet (MSDS) for the product or reagent that contains Hydrofluoric Acid. Be sure it is the MSDS for the specific formula you are using. Call the supplier for additional information if necessary.

 

    1. Have a standard operating procedure (SOP) for your particular operations, safety precautions, emergency procedures, and waste disposal involving HF and train all that work with or around HF so they are aware of procedures before use. A HF template is available to assist with generating a SOP.

 

    1. Be sure that you are using personal protective equipment that has been shown to effectively protect against Hydrofluoric Acid exposure. Always double check your personal protective equipment before each use of HF. A pinhole in a glove or leaky container can cause an accident you really want to avoid at all costs. HF burns penetrate deeply into skin and muscle tissue and can’t be treated by simply flushing the area with water.

 

  1. Before using Hydrofluoric Acid, be sure you have a clear idea of what you will do in the event of a skin exposure, eye exposure, etc. involving Hydrofluoric Acid. First aid and medical treatment for HF exposure is very specific and critical. Be sure to have Calcium Gluconate on hand. The special nature of the reaction of the fluoride ion with calcium in human tissue requires immediate, often heroic measures to save digits, limbs and even lives. The HF Acid website is a good source of information on working safely with HF, including proper personal protective equipment while using HF, information of storage, handling and processing and “Recommended Medical Treatment for Hydrofluoric Acid Exposure” (Honeywell).

It is highly recommend that you contact your first aid or emergency medical provider to assess whether they are knowledgeable about and equipped to handle Hydrofluoric Acid-related incidents.

  • Also, before using Hydrofluoric Acid, you should review what you would do in response to a leak or spill. Some conventional spill cleanup materials are readily dissolved by Hydrofluoric Acid. Special materials are needed to clean up Hydrofluoric Acid spills. After hours, it may be necessary to ask the University Police (campus phone 9-911 or cell 414-229-9911) to have the Milwaukee HazMat Team respond to a spill.

 

  • Be sure that you know how to neutralize Hydrofluoric Acid waste. If your Hydrofluoric Acid acid waste is going to be contaminated with any other hazardous materials (heavy metals, for example), contact staff in UWM’s Environmental Protection Program (phone: x6339) before generating the waste. By consulting with the program manager, the generation of hazardous wastes can be reduced both to protect the environment and to conserve limited waste disposal funds.

For further information, contact your professor, supervisor, principal investigator or Environmental Protection staff (x6339).

Mercury Spill Clean-up Procedures

Mercury Spill Cleanup PowerPoint Presentation on Mercury Spill Clean-Up Procedures

Mercury (Hg) is defined as a hazardous material by the U.S. Environmental Protection Agency and the Wisconsin Department of Natural Resources. Moreover, mercury is a toxic substance that can result in severe health effects. Therefore, all mercury “spills,” including droplets of mercury from a broken laboratory thermometer, need to be cleaned up following safe and environmentally sound procedures.

Questions regarding mercury or spill procedures should be directed to your professor, a laboratory supervisor, your own supervisor or the UWM Department of University Safety & Assurances (US&A). Starting in January 2002, departments have to pay for cleanup of mercury in one of three ways:

  • Call US&A for list of outside contractors
  • Pay US&A a flat fee of $50 for cleanup services
  • Have the person who spilled the mercury learn how to use the campus mercury vacuum and have them clean up the spill. The Department of University Safety & Assurances will provide, at no charge, mercury air-monitoring, advice and support.

The following video clip (courtesy of Minuteman International, Inc., Addison, IL) shows how to replace the HEPA filter bag in the mercury vacuum: Mercury Vacuum HEPA Filter Bag Replacement Instructions

For further information on mercury spills on campus, please contact Environmental Affairs at x4999 or x2883.

Information on Household Spill Clean Up:

Metallic Mercury Exposure

Metallic mercury is a hazardous chemical that can cause serious health problems. Children (especially very young children) and fetuses are most vulnerable. The Agency for Toxic Substances and Disease Registry (ATSDR), part of the U.S. Public Health Service, and the Environmental Protection Agency (EPA) are jointly issuing an alert to the general public. There is a continuing pattern of metallic mercury exposure in children and teenagers and in persons using certain folk medicines or participating in certain ethnic or religious practices.

It is important for the general public to understand that either short-term or long-term exposures to metallic mercury can lead to serious health problems. Human exposure to metallic mercury occurs primarily from breathing contaminated air. Other forms of mercury can be absorbed by drinking contaminated water, eating food (usually fish containing mercury), and from skin contact. At high levels, metallic mercury can cause effects on the nervous system and the developing fetus. Other forms of mercury can damage other organs. Even at low levels, metallic mercury can cause health problems. Metallic mercury exposure can cause harm before symptoms arise. Once released into the environment, mercury is very hard to clear up. If it is left unattended where exposures can occur, it can have dangerous effects on human health.

Incidents Involving Schoolchildren

In recent years, increasing numbers of metallic mercury spills and contamination involving schoolchildren have been reported:

In August 1994, more than 500 students in Belle Glade, Florida, were contaminated with metallic mercury after three children found 4 jars (totalling 55 pounds) of metallic-mercury in an abandoned van. The local hazardous waste materials team decontaminated the children (removed contaminated clothing and washed the metallic mercury from their skin). More than 20 families had to be evacuated while their homes were decontaminated.

In November 1994, college students at Florida Atlantic University in Boca Raton, Florida, removed metallic mercury from one of the school’s laboratories. Students living in the dormitory were evacuated and housed in a local hotel while the dormitory was decontaminated.

In June 1996, metallic mercury was taken from a middle school in St. Joseph, Missouri, and used in and outside of school by a group of teenagers. Approximately 200 children were tested for mercury exposure; one child was hospitalized and another five underwent outpatient treatment to remove the mercury from their systems; 20 other children had mildly elevated mercury levels. Two homes and a car required extensive decontamination.

In October 1996, a high school in Oskaloosa, Kansas and a convalescent home in Johnson County, Kansas, were contaminated with metallic mercury; 52 students and an unknown number of residents of the home were tested. On the basis of ATSDR recommendations, the school was closed for a week until indoor air levels were safe. A month later, sampling at the school identified an increase in air mercury concentrations. The school was re-evaluated and additional clean-up was done as recommended by ATSDR.

In November 1996, ATSDR again assisted state health officials and EPA in evaluating contamination at a high school and a home in Dallas, Pennsylvania, near Wilkes-Barre. Four areas in the school had levels of metallic mercury contamination that required cleanup.

In March 1997, a middle school student on his way to school found metallic mercury on the street in front of his home in Montgomery County, Pennsylvania. The student took the metallic mercury to school and shared it with three to four classmates. Also, in March 1997 a broken mercury thermometer was discovered after school on the floor of a bathroom stall in the boys bathroom. One thermometer was confirmed missing from the science department’s inventory. The school was found to be clear of contamination with the exception of one science laboratory and the carpet in a classroom. Two homes required decontamination.

Schoolteachers, particularly science teachers, and administrators need to be aware of students’ interest in mercury, especially metallic mercury, and take steps to ensure that children are aware of its dangers and that any mercury kept in school is safely and securely contained.

Incidents Involving Religious Practices

Persons who use metallic mercury in ethnic folk medicine and for religious practices are at risk. Metallic mercury is sold under the name “azogue” in stores (sometimes called botanicas), which specialize in religious items used in Esperitismo (a spiritual belief system native to Puerto Rico), Santeria (a Cuban-based religion that venerates both African deities and Catholic saints), and voodoo.

The use of azogue in religious practices is recommended in some Hispanic communities by family members, spiritualists, card readers, and santeros. Typically, azogue is carried on one’s person in a sealed pouch prepared by a spiritual leader or sprinkled in the home or automobile. Some botanica owners suggest mixing it in bath water or perfume and placing it in devotional candles.

General Facts

The following are general facts about metallic mercury and its risks, as well as information about how people can protect themselves from exposure and resulting health effects.

What is Mercury and How is it Used?

Mercury occurs naturally in the environment in several forms. Metallic Mercury is the liquid form used in thermometers. Mercury is also used in other common consumer products such as fluorescent light bulbs, barometers, medical equipment such as blood pressure measurement instruments, and mercury switches in children’s sneakers that light up. This alert concentrates on metallic mercury, but hazards are also associated with other types. Of these, the most common is methyl mercury contamination of fish.

How Could I be Exposed to Mercury?

In the previously described school-associated cases, children were unaware of the dangers involved in exposing themselves and their families to this deadly poison. Adults are also often unaware of the hazards associated with mercury; some have even brought it home from work for children to play with. Just one-half teaspoon of mercury spilled in the home can be dangerous.

Adults using certain folk medicines or participating in certain religious or ethnic practices may also expose themselves and their families to metallic mercury’s effects. Because metallic mercury vaporizes into the air at room temperatures, it presents an immediate health risk to anyone spending a significant amount of time in a room where metallic mercury is sprinkled or spilled onto the floor, or where opened containers of metallic mercury are present. Very small amounts of metallic mercury (for example, a few drops) can raise air concentrations to levels that may be harmful to health.

How Does Mercury Affect Health?

At high levels, metallic mercury can cause effects on the nervous system and the developing fetus. Other forms of mercury can damage other organs. Even at low levels, metallic mercury can cause health problems. Mercury exposure can begin to cause harm before symptoms arise. Once symptoms do arise, health problems related to metallic mercury poisoning can include tremors, changes in vision or hearing, insomnia, weakness, difficulty with memory, headache, irritability, shyness and nervousness and a health condition called acrodynia.

Pregnant women and their fetuses are especially vulnerable to the toxic effects of metallic mercury because it readily passes from the placenta to the fetus. Mercury may accumulate in higher concentrations in the unborn baby than in the mother. Young children, who often play on the floor where metallic mercury may have been spilled, are particularly at risk for effects on the central nervous system. Mercury vapors are readily absorbed into the bloodstream from the lungs, and the human central nervous system, which is still developing during the first few years of life, may become damaged.

Health effects can result from short-term or long-term exposure. The body gets rid of mercury through the urine and feces. Removal of this substance from the body can take up to several months after exposure. Acrodynia is characterized by itching, swelling, and flushing; pink-colored palms and soles of the feet; excessive perspiration; rashes; irritability; fretfulness; sleeplessness; joint pains and weakness. Children exposed to metallic mercury for long periods may have trouble learning in school. When mercury levels in the body are extremely high, “chelation” therapy is necessary. Chelation therapy involves putting a chemical into the bloodstream; the chemical combines with the mercury to aid in its removal from the body.

Prevention is the key to avoiding poisoning in homes, schools and families.

What is Mercury Contamination and How Can I Prevent It?

First, avoid using metallic mercury. Appropriate substitutes are available for nearly all uses of metallic mercury. Therefore, be sure you need to use it. If not, make arrangements to safely dispose of whatever metallic mercury you might have. If you do need to use metallic mercury, make sure it is safely stored in a leakproof container. Keep it in a secure space (e.g., a locking closet) so that others cannot easily get it. Use of metallic mercury in a controlled environment helps to reduce the risk that contamination will occur.

Mercury contamination results from exposure through the air, water, food, soil, or direct contact. Exposure to metallic mercury occurs when it is not stored in a closed container. Contamination may include the spilling of metallic mercury on clothes, furniture, carpet, floors, walls, the natural environment, and even the human body. Metallic mercury and its vapors are extremely difficult to remove from such items as clothes, furniture, carpet, floors, and walls. The vapors will also accumulate in walls and other structures in contaminated rooms. The contamination can remain for months or years, posing a risk to exposed individuals. The use of metallic mercury in a home or apartment not only poses a threat to persons currently residing in that structure, but also to those who subsequently occupy that dwelling and are unaware of the past mercury use.

Can I Clean Up Mercury with a Vacuum Cleaner?

Never use a vacuum cleaner. Using a vacuum cleaner causes metallic mercury to vaporize in the air, creating greater health risks. It also ruins the vacuum cleaner.

Can Electronic Equipment Collect Mercury Vapors?

Metallic mercury vapors can accumulate in electronic equipment, especially computers. When the computer is turned on, the mercury revaporizes. This cycle of metallic mercury collecting and vaporizing from computers has been seen in several incidents in schools.

What Should I do to Keep my Home Safe?

Metallic mercury is used in a variety of household and industrial items including thermostats, fluorescent light bulbs, barometers, glass thermometers, and some blood pressure machines. Care must be taken in handling and disposing of all items in the home that contain metallic mercury.

First, DO NOT try to vacuum or heat the metallic mercury in any way. Mercury vapors are very dangerous and are virtually undetectable. Avoid breathing mercury dust, vapor, mist, or gas. Avoid contact with eyes, skin, and clothing. If you feel you have been exposed directly to metallic mercury, wash thoroughly after handling. Remove contaminated clothing and wash before reuse. Provide as much clean air as possible.

For example, if a thermometer breaks, remove children from the area. Clean up the bead of metallic mercury by carefully rolling it onto a sheet of paper or sucking it up with an eye dropper. After picking up the metallic mercury, put it into a bag or airtight container. The paper or eye dropper should also be bagged and disposed of properly according to guidance provided by environmental officials or your local health department. Try to ventilate the room to the outside and close off from the rest of the home. Use fans for a minimum of one hour to speed the ventilation. If larger amounts of metallic mercury are found (for example, a jar), make sure that the metallic mercury is in an airtight container and call your local health department for instructions in how to safely dispose of it. If the larger amount is spilled, leave the area and contact your local health department and fire authorities. Do not simply throw it away, but instead seek professional guidance.

ATSDR and EPA do not recommend the use of uncontained metallic (liquid) mercury (that is, mercury not properly enclosed in glass as it is in thermometers) in homes, automobiles, day care centers, schools, offices, and other public buildings.

Important Telephone Numbers

  • Agency for Toxic Substances and Disease Registry (ATSDR) Emergency Response Hotline (24 hours): 1-404-498-0120
  • ATSDR General Information: 1-404-498-0110
  • National Response Center: 1-800-424-8802
  • Superfund Information Hotline: 1-800-424-9346
  • You may also call your local health department

A Warning About Continuing Patterns of Metallic Mercury Exposure, Issued jointly by EPA and ATSDR, 6/26/97

Picric Acid Safety

General Information

Picric Acid

Picric Acid is distributed by the manufacturers wet with greater than 10% water. It is a tri-nitro compound that is normally classified as a flammable solid. As the water evaporates over time, the substance becomes dry picric acid crystals. Dry picric acid is highly explosive especially when it is combined with metals such as copper, lead, zinc and iron. It will also react with alkaline materials including plaster and concrete to form explosive materials. This material is shock sensitive and corrosive to metal containers.

Picric Acid is often found in science laboratories and chemical storage rooms and is used for staining of cells during biology experiments.

Identifying Problem Containers

The normal appearance of solid picric acid is a fine, moist yellow powder, with the consistency of a clumpy paste, which tends to adhere to the sides of the bottle. Picric acid makes a clear yellow solution, sometimes with undissolved solid powder in the bottom. Whether a solid or in solution, there should be no crystals.

Caution! If there are signs of crystalline material in the bottle neck, threads, or around the cap; or if the product inside appears powdery and to have dried out completely, do not move or handle the container and contact University Safety and Assurances staff for assistance.

Inventory Management

Purchase picric acid in quantities of no more than 100 grams to increase the likelihood that it will be used up before it becomes a problem. Store picric acid at a controlled temperature in a visible location within a flammables storage cabinet.

When receiving fresh product from the distributor review the MSDS for a material description and manufacturer’s handling recommendations. Visually inspect the container. Do not open or use the product if it has exceeded its manufacturer’s expiration date or does not appear normal.

Do not break the seal on the container until the product is needed. Label it with the date it is first opened. Add additional deionized water to solid picric acid as soon as it is first opened. If it does not interfere with its intended use, add enough water to immerse the product.

Use

Visually inspect the container for problems prior to each use and on a periodic basis (not less than every semester). After each use, take care to wipe down the bottleneck, cap and threads with a wet cloth before resealing. Thoroughly clean and rinse any secondary containers used immediately following the procedure. Add distilled water as needed to maintain its wet condition.

Maintain a log of the product’s use and any water additions. This record will aid the Environmental Affairs staff in determining how to best handle the product for disposal.

Picric acid reacts with many metals to form highly unstable and shock sensitive metal picrates. Do not allow picric acid to contact metal that is readily oxidized. Do not transfer it to a container with a metal cap, or use a metal spatula to dispense it. It also reacts with calcium from cement floors to form shock-sensitive calcium picrate.

Read the Material Safety Data Sheet (MSDS) for the product or reagent that contains picric acid. Be sure it is the MSDS for the specific formula you are using. Call the supplier for additional information if necessary.

If a container of Picric Acid of unknown vintage is found, DO NOT attempt to open the container. Treat ALL containers of Picric Acid as if the acid has dried. The container could explode from friction on the crystals between the grooves of the cap and the threads.

If anyone has Picric Acid stored in their labs, please consider getting rid of it. You can request a pickup by completing the on-line E-Request for Chemical Waste Pickup or by calling x2883 or x4999. If you haven’t used the Picrid Acid recently, please do not move it or disturb the cap in any way. Picric Acid is now sold in a 1% solution in water, which is much safer, but you still have to watch out for crystals forming under the cap. When Picric Acid is purchased, put the date received on the bottle. Dispose of any Picric Acid over 1-year old.

For further information contact your professor, supervisor, principal investigator or the Environmental Affairs Program staff located in Lapham Hall, Room 248 (x4999 or x2883).

Lead Information

Modern building with lead-coated copper sheeting on exterior wall

General Information

Lead (Pb) is a metal. Lead melts easily and quickly, and it can be molded or shaped into thin sheets and can be drawn out into wire or threads. Lead also has great resistance to different weather conditions. Unfortunately, lead and lead compounds are toxic and can present a severe hazard to those who are overexposed to them. Whether ingested or inhaled, lead is readily absorbed and distributed throughout the body.

Historically, lead has been used in a variety of applications because of its aesthetic beauty, unique properties and durability. For example, this modern building’s exterior wall (the gray center portion) is lead coated copper sheeting.

How are People Exposed to Lead?

Lead is widespread in the environment, and people absorb lead from a variety of sources every day. Although lead has been used in numerous consumer products, the most important sources of lead exposure to the general population are:

  • Soil and Dust (which has been contaminated by air, and includes dust both inside and outside the home)
  • Food (which can be contaminated by lead in the air or in food containers, particularly lead soldered food containers)
  • Drinking Water (from corrosion of plumbing systems)
  • Lead Based Paint
  • Occupational Exposure, or Hobbies

On average, it is estimated that lead in drinking water contributes between 10-20% of total lead exposure in young children. Food is the greatest single source of lead for the average adult. In the past few years, federal controls on lead in gasoline and from industrial air emissions have significantly reduced total human exposure to lead.

How Does Lead Affect Human Health?

Lead absorbed by the lungs and the digestive tract from all sources enters the bloodstream, where it distributes to all tissues of the body. Excessive levels of lead can damage the brain, kidneys, nervous system, red blood cells and reproductive system. The degree of harm is directly related to the level of lead in the blood (from all sources). Known effects of exposure to lead range from subtle changes in body chemistry and nervous system function at low levels of exposure, to severe toxic effects or even death at very high levels associated with acute poisoning. Some harmful effects are reversible if exposure is reduced, while other harmful effects can be permanent.

Does Lead Affect Everyone Equally?

Young children, infants and fetuses appear to be particularly vulnerable to harmful effects of lead. A dose of lead that would have little effect on an adult can have a significant effect on a small, developing body. Also, growing children will more rapidly absorb any lead they consume. A child’s mental and physical development can be irreversibly stunted by overexposure to lead. In infants, whose diet consists of liquids made with water, such as baby formula, lead in drinking water makes up an even greater proportion of total lead exposure (40-60%).

Occupational Exposure to Lead

Lead has been poisoning workers for thousands of years. In the construction industry, traditionally most overexposures to lead are found in the trades, such as plumbing, welding and painting. Significant lead exposures can also arise from removing paint from surfaces previously coated with lead-containing paint, such as in bridge repair, residential renovation, and demolition.

Hobbies resulting in lead exposure may include firearm practice, soldering in jewelry making or stained glass work, and ceramics.

Exposure to lead may result when lead or any product containing lead is heated, especially above 500 degrees C (932 degrees F). Lead dust exposure may result from such operations as pouring powders containing lead, sanding or sandblasting surfaces coated with lead based paints.

Very small amounts of lead that may be unintentionally ingested via eating, drinking, or smoking on the job or through hobbies can be harmful. Good personal hygiene is important where lead is present.

Worker awareness and training are important so that employees can recognize the symptoms of exposure and get prompt medical attention. Jobs involving potential lead exposure should be targeted for detailed evaluation of their potential for lead exposure.

OSHA regulates lead for employees who work in the private sector. In Wisconsin, DCOM enforces the same regulations for public sector employees. The OSHA lead regulations (29 CFR 1910.1025 and 29 CFR 1926.62) require:

  • If a worker works with lead, the employer must test the air for lead levels.
  • If the lead level in the air is 30 micrograms per cubic meter of air or greater, the employer must offer employees routine blood testing.
  • An employee must be removed from all exposure to lead if the average blood level is 50 micrograms/deciliter or more on three tests. He or she cannot return to an environment where lead is present until the blood level falls to at least 40 mcg/dl.
  • The standard also establishes requirements for medical monitoring, respiratory protection, protective clothing, engineering controls and ventilation, work practice controls, hygiene facilities, and employee education.

OSHA and DCOM require employers to reduce airborne lead exposure below the OSHA Permissible Exposure Limit (PEL). The best way to do this is to simply replace lead and products that contain lead with less toxic materials. If this is not possible, the employer must provide change rooms and lockers, showers, and a thorough cleaning of work surfaces. There can be no smoking or eating in work areas. The employer must also provide training to employees on the hazards of lead and on the OSHA lead standard. Currently, there is no OSHA standard which provides a permissible limit for lead contamination of surfaces in occupational settings.

Lead dust can settle on your clothes and if these are not changed before going home, family members can be exposed. Lead can stay on your skin, hair, and on your shoes, lunch bucket, bookbag, etc. Young children are more sensitive to lead than are adults and can have health problems from exposure to less lead. If you are concerned, you can have your child’s blood lead tested. Contact your physician or local health department for additional information.

For work involving lead at UWM, please contact the Department of University Safety and Assurances for a workplace lead exposure evaluation.

Sources

  • Lead in Drinking Water, Wisconsin Department of Natural Resources
  • Occupational Lead Fact Sheet, Wisconsin Division of Health, 1992.
  • Working with Lead in the Construction Industry (OSHA 3126), U.S. Department of Labor, Occupational Safety and Health Administration, 1991.

Lead Paint Information

Background Information:

Chipping Lead-Based Paint

The Department of Physical Plant Services maintains an inventory of lead-based paint application at UWM. Please remember that not all materials have been tested or labeled. If in doubt as to whether a material is lead-based paint make sure to have it analyzed before disturbing it.

Lead paint results are reported in either mass loading (milligrams lead per square centimeter), or mass concentration (parts per million, parts per billion, or percent by weight). There is no conversion relationship between the two unit reporting types. Field portable non-destructive x-ray fluorescence (XRF) instruments report the concentration of lead in paint as mass loading (milligrams lead per square centimeter). Destructive sampling methods utilizing laboratory analysis are reported as mass concentration (ppm, ppb, or % by weight).

Inexpensive qualitative field test kits are now commercially available for the detection of lead-based paint. These devices simply give a positive or negative result (i.e., not quantitative). These kits are useful survey tools, but they may give false negatives and the results are subject to tester interpretation. For additional information on home test kits, please see: U.S. EPA Office of Pollution Prevention and Toxics Interpretive Guidance For The Federal Program TSCA Sections 402/403.

Lead-Based Paint Disclosure for UWM Student Housing:

The EPA/HUD Lead-Based Paint Disclosure Rule (Section 1018, March 6, 1996) of TSCA’s Title IV is intended to ensure family health. It requires the disclosure of known information on lead-based paint and/or lead-based paint hazards before the sale or lease of housing built before 1978. Section 1018(a)(1)(B) requires that ”before the purchaser or lessee is obligated under any contract to purchase or lease the housing, . . .the seller or lessor shall. . .disclose to the purchaser or lessee the presence of any known lead-based paint or any lead-based paint hazards, in such housing, and provide any lead hazard evaluation report available to the seller or lessor.”

The disclosure rule exempts university dormitory housing and other ‘zero bedroom’ dwellings. Please contact Physical Plant Services for environmental survey information of Sandburg and Purin Halls.

Guidelines/Standards:

Paint:

There is no universal definition of lead-based paint. Since 1977, The Consumer Product Safety Commission has limited the lead in most paints to 0.06% (600 ppm by dry weight). Paint for bridges and marine use may contain greater amounts of lead (ATSDR, 2000).

Lead-based Paint Definition:
(The Lead Exposure Reduction Act, Section 401, Title IV, TSCA amendment, Public Law 102-550, 1992; Title X of the1992 Housing and Community Development Act)

>0.5% (5,000 ppm)

or >1.0 mg/cm2

Lead-free Paint Definition:
(Consumer Product Safety Act, CPSA 15 USC 2057-8, 1978)
<0.06% (600 ppm)
Lead-based Paint Definition:
(State of Wisconsin)
>0.06% (600 ppm)

Please Note: Regardless of which definition is used, exposure to airborne lead or lead dust contamination may still occur as a result of removing paint or other surface coatings that contain even small amounts of lead.

U.S. EPA and U.S. Housing and Urban Development (HUD) Lead Paint Abatement Clearance Level Requirements:

Floors: <50 ug lead/square foot
Window Sills: <250 ug lead/square foot
Window Wells (Exterior Sills): <800 ug lead/square foot
(400 ug lead/square foot proposed rule)
All other surfaces: <100 ug lead/square foot

These levels have been established as achievable through lead abatement and interim control activities. They are not based on projected health effects associated with specific surface dust levels. There is currently no OSHA standard which provides a permissible limit for lead contamination of surfaces in occupational settings.

Sources and Regulations Regarding Lead-Based Paint, Abatement and Worker Protection:

Questions regarding lead paint application other than at UWM should be directed to your local health department. Many private laboratories and firms in the Milwaukee area also provide lead testing and consultation services.

Lead in Soil

Modern building with lead-coated copper sheeting on exterior wall

Uncontaminated soil contains lead concentrations of less than 50 ppm, but soil lead levels in many urban areas exceed 200 ppm (American Academy of Pediatrics, 1993).

Contaminated soils can contain much higher levels.

EPA has established 400 mg/kg for lead in residential soils as a guidance value that would be protective of public health. This value is for guidance only and is not enforceable.

Physical Plant Services is currently monitoring the lead contamination in soil caused from the lead-coated copper sheeting of this modern building.

Sources:

Lead in Water

Lead is a toxic substance which accumulates in the body and can cause serious health problems. New laws have been passed because lead is unhealthy for humans, especially children. Small amounts of lead that would not harm an adult can disrupt a child’s normal growth and mental development.

Few waters contain naturally high sources of lead. The use of lead solder and other lead-containing materials in connecting household plumbing to public water supplies was banned by EPA as of June 1988. Many older structures still have lead pipe or lead-soldered internal plumbing which may substantially increase the lead content of water at the tap. Regulations controlling the lead content of drinking water coolers in schools went into effect in 1989 (ATSDR, 2000).

Federal and State laws require the Milwaukee Water Works to treat the water to reduce lead. The lead is continuously leached into the water by plumbing materials containing lead, such as lead pipes, lead solder on copper pipes, or brass fixtures. The rate can vary greatly with the variations in natural water quality and the age of the plumbing system. When the water stands motionless for extended periods of time, such as overnight, lead concentrations in the water can sometimes increase greatly. There is no detectable lead in water leaving the Milwaukee treatment plants. (Please refer to the The Milwaukee Water Works Annual Water Quality Report 2008 pdf document, Adobe Acrobat Required for most recent information.)

The allowable amount of lead in drinking water has been lowered from 50 parts per billion (50 ppb) to 15 ppb. Levels slightly above the standard do not necessarily signify a health hazard.

The Water Works has chosen to add phosphate to the water to reduce lead leaching from interior pipe surfaces containing lead. The phosphate forms a very thin coating on interior pipe surfaces to keep lead from dissolving into water. Many other water utilities across the U.S. are taking similar measures. The phosphate is added in the form of phosphoric acid (70 percent H3PO4). Starting in early September 1996, the level will be 3 parts per million (ppm) phosphate. The Water Works anticipates that lead levels will drop below the maximum allowed limit after 1 year, and they hope to subsequently reduce the phosphate dose to 1 ppm (as PO4).

The Department of Physical Plant Services maintains an inventory of water tests conducted for lead at UWM. Analysis for lead in water is performed by Zeeman-platform graphite furnace atomic absorption spectrophotometry.

It is generally recommended that water be run for a few seconds the first time it is used each day, or until it reaches its coldest temperature, before being used for consumption in order to minimize any possible lead contamination.

Questions regarding water quality other than at UWM should be directed to your water utility or to one of the Wisconsin Department of Natural Resources’ (DNR) district offices. The Wisconsin DNR website is a good source for general information about lead in Wisconsin’s drinking water. Questions pertaining to exposure to lead and its potential effects on your health should be directed to your family physician or your local health department.

Sources: