Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Job Classification

In most duration tables, five job classifications are displayed. These job classifications are based on the amount of physical effort required to perform the work. The classifications correspond to the Strength Factor classifications described in the United States Department of Labor's Dictionary of Occupational Titles. The following definitions are quoted directly from that publication.

Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Toxic Effects, Hydrofluoric Acid


Related Terms

  • Anhydrous Hydrofluoric Acid Poisoning
  • Fluorhydric Acid Poisoning
  • Fluoric Acid Poisoning
  • Hydrogen Fluoride Hydrofluoride Poisoning

Specialists

  • Medical Toxicologist
  • Pharmacologist
  • Preventive Medicine Specialist

Factors Influencing Duration

The levels and length of time exposed, method of exposure, immediacy of treatment, and the individual's response to exposure and treatment determine length of disability. The location of burns has an influence on the individual's ability to recover. Age, general physical condition, and pre-existing disease influence the individual's ability to recover pre-injury functional capacity and return to work.

Medical Codes

ICD-9-CM:
983.1 - Toxic Effect of Corrosive Aromatics, Acids, and Caustic Alkalis, Hydrofluoric Acid; Nitric Acid; Sulfuric Acid

Overview

Hydrofluoric acid (hydrogen fluoride, HF, or H2F2) is a colorless, fuming liquid or colorless gas with a strong irritating odor. Hydrogen fluoride is extremely reactive. Exposure to HF and its aqueous solution can occur through inhalation, ingestion, and eye or skin contact. HF as a gas is a severe respiratory irritant, and in solution it causes severe and painful burns of the skin and eyes. Inhalation of HF produces transient choking and coughing. After a symptomatic period of several hours up to 1 to 2 days, fever, cough, dyspnea, cyanosis and pulmonary edema may develop. Repeated exposures to excessive concentrations over years have resulted in a crippling fluorosis due to deposition of fluoride in bone.

HF solutions in contact with skin result in marked tissue destruction, prolonged tissue damage, and deep burns. Undissociated HF readily penetrates skin and deep tissue where the corrosive fluoride ion can cause necrosis of soft tissues: the tissue damage is excruciatingly painful. Tendinitis and tenosynovitis may result. The process of tissue destruction and neutralization of HF is prolonged for days, unlike other acids, which are rapidly neutralized. Due to the insidious manner of its penetration, a relatively mild or minor exposure can cause a serious burn. Delayed recognition of contact with dilute solutions often results in more severe burns than expected. Severe eye injuries from splashes have been reported.

Exposures to potentially toxic levels of HF may occur where workers are engaged in its manufacture and transportation, or where it is used as an acidizing agent during injection of acid into oil wells. Individuals may also be exposed when the fluorides are liberated during manufacture of fertilizer and the burning of coal and when used to stop fermentation in brewing. Other methods of exposure include the etching of silicon wafers in semiconductor manufacturing, purification of filter paper and graphite, enameling, and the galvanizing of iron.

Workers may be exposed to aqueous HF when removing sand and scale from foundry castings, treating textiles to remove trace metals, and preparing microelectronic circuits and radio parts. Exposure may also occur in the etching, frosting, and polishing of glassware and ceramics; electroplating operations; cleaning sandstone and marble; when used as a pickling agent for stainless steel and other metals; and as a cleaner in the meatpacking industry.

Anhydrous HF exposure may occur in the manufacture of solvents, high-performance plastics, and foaming agents. Exposure to HF may also occur in the manufacture and production of fluorosilicate products, pharmaceuticals, and special dyes.

Incidence and Prevalence: 1,159 people were exposed to HF in 2002 according to the American Association of Poison Control Centers Surveillance System. Of those, 23 lives were endangered from the exposure to HF meaning they were disabled or suffered a serious complication such as cardiac arrest, and 5 died (Watson).

Source: Medical Disability Advisor



Causation and Known Risk Factors

Men are more likely to be exposed to HF than women (Wilkes).

Source: Medical Disability Advisor



Diagnosis

History: The individual may complain of difficulties breathing (choking and coughing), as well as burning sensations on the skin and the eyes.

Symptoms include severe eye, nose and throat irritation; delayed fever, cyanosis and pulmonary edema; and severe and painful skin and eye burns from splashes of solutions. Prolonged or repeated exposure to low concentrations of the gas may cause nasal congestion and bronchitis.

Physical exam: Patients may have painful burns on their skin and eyes with redness, swelling and blisters. Pulmonary edema can occur after an individual inhales HF.

Tests: Pulmonary function tests, chest x-rays, and arterial blood gases may be helpful. Endoscopy or bronchoscopy may be needed to evaluate burns in the respiratory and digestive tract. The cornea is examined with a slitlamp using fluorescein dye. Pelvic x-rays may be done to show the early signs of increased bone density from fluoride deposition. These signs are most apparent in the lumbar spine and pelvis. Digital x-rays should be done to evaluate bone integrity if there are burns to the fingers. Electrocardiograms (ECG) may be necessary for cardiac monitoring if burns are significant. Serum electrolytes can be helpful in ruling out abnormalities in calcium, magnesium and potassium levels.

Fluoride concentration in urine is a useful index for exposure to HF and has been found to average about 4 mg/L in an end-of-shift specimen following an 8-hour exposure to 3 parts per million (ppm) of HF. Dietary intake of water high in fluoride may increase the urinary fluoride concentration.

Source: Medical Disability Advisor



Treatment

The high-risk of either immediate or delayed onset of pulmonary edema following inhalation of the gas requires that oxygen be administered immediately after a severe exposure. If the individual has inhaled the HF, they may also be treated with a 2.5% calcium gluconate nebulizer (Wilkes). Close observation should be continued for 24 to 48 hours. The treatment is similar to that of noncardiogenic pulmonary edema from other causes. The value of systemic steroids has not been established.

Persons who have had skin contact with HF should be immediately showered for at least 10 minutes. Contaminated clothing should be removed as quickly as possible. The affected area should be immediately soaked with iced solutions of quaternary ammonium compounds. An iced solution of Epsom salts or a calcium gluconate gel is acceptable for topical therapy. If the burns appear to be deep or if there is exquisite pain, particularly if the concentration of acid was greater than 20%, the painful areas should be cautiously injected with 10% calcium gluconate. If the burns involve the fingers, injections are not recommended but the individual may be treated with IV calcium gluconate. If the individual has burns on their eyes, the eyes may be rinsed with saline or water for a minimum of 5 minutes; however, if the individual continues to complain of eye pain, rinsing with 1% calcium gluconate solution may be helpful. The individual may need local anesthesia to help control pain.

Source: Medical Disability Advisor



Prognosis

Prognosis for successful recovery varies depending on severity and location of the burn. Effects of mild exposure resolve with treatment.

The prognosis for a successful outcome is poor following fluoride inhalation. Severe inhalation can cause lung damage and chronic lung disease with profound disability. The surface appearance of skin exposed to HF cannot predict the seriousness of the damage, which may be severe and delayed as the fluoride ion aggressively and destructively penetrates deeply into tissues and acts as a serious systemic poison.

The cornea may become opaque with decreased vision, blindness, and total eye destruction. The effect on the level of calcium in the blood can be so profound as to cause death. Repeated exposure via ingestion or inhalation of fluorides can result in mottled teeth, the accumulation of fluoride in bones, osteosclerosis, and kidney and liver damage. Skin lesions take a long time to heal and can result in extensive scarring.

Source: Medical Disability Advisor



Rehabilitation

Any toxic condition caused by HF may warrant rehabilitation if the condition affects the respiratory system, results in bone deformities, general weakness, and/or causes a loss of vision. Once initial symptoms are stabilized and a physician determines no contraindications to physical activity, the rehabilitation professional initiates a gradual strengthening program.

If necessary, individuals are instructed in respiratory exercises to improve ventilation to reduce breathing difficulties. Rehabilitation uses several techniques to assist the muscles that aid in breathing. These may include instructing the individual to assume relaxed sitting postures, and strengthening secondary respiratory muscles.

Once breathing returns to normal, individuals rehabilitating from this toxic condition progress to strengthening and endurance exercises with aerobic-type activities that increase individuals' ability to work and help them resist fatigue. As endurance increases without shortness of breath, the individual begins active upper and lower extremity exercises with progressive resistance using free weights and/or weight machines. Frequency of the program may vary somewhat depending on the individual's general health. If tolerated, the individual performs strengthening exercises 3 times a week and aerobic activities on the non-strengthening days of the program.

In the event the condition has caused an increased bone density from fluoride deposition, long-term physical therapy may be necessary if significant bone malformations and disorders have occurred. This includes exercises to help maintain mobility of the spine and other joints involved. A flexibility program is one of the priorities when the lumbar spine is affected by the condition. The individual may be instructed in several stretching exercises, as well as exercises to strengthen the lower back and abdominal muscles.

General muscle weakness is addressed with strengthening exercises and education regarding the importance of remaining as active as possible with enjoyable activities. If exercises are tolerated well, resistance is then progressively added to each exercise to build strength in order to return to work/functional activities. It may also be necessary for the rehabilitation program to address any loss of balance and coordination this toxic condition may have had on the nervous system.

A speech therapist trained in swallowing evaluations becomes involved in the rehabilitation program if the condition has caused swallowing difficulties (dysphagia) or speech impairments. If there is impaired or permanent loss of vision from this condition, occupational therapy may help individuals adapt to their surroundings and assist in retraining them in activities of daily living (i.e., dressing and grooming).

The rehabilitation program varies for individuals affected by the toxic effects of HF. Individuals should be trained in the proper lifting of heavy objects especially if bone density in the spine has changed. Rehabilitation of the lumbar spine also helps prepare the individual to return to work. The intensity and progression of exercises depend on the body organs affected (specifically the respiratory system) and the individual's overall health.

Source: Medical Disability Advisor



Complications

There are several complications of HF exposure which include loss of vision, loss of fingers, scarring, irregular heartbeat, corneal damage, abnormalities of electrolytes, a fluid accumulation in the lungs, systemic fluorosis, and airway compromise.

Source: Medical Disability Advisor



Ability to Work (Return to Work Considerations)

The Occupational Safety and Health Administration's (OSHA) legal airborne permissible exposure limit (PEL) is 3 ppm averaged over an 8-hour work shift.

The National Institute of Occupational Safety and Health's (NIOSH) recommended airborne exposure limit is 3 ppm averaged over a 10-hour work shift, and 6 ppm not to be exceeded during any 15-minute work period.

The American Conference of Governmental Industrial Hygienists' (ACGIH) recommended airborne exposure limit is 3 ppm, not to be exceeded at any time.

Hazard and warning information should be posted in the work area. As part of an ongoing education and training effort, individuals should be given all information on the health and safety hazards of hydrogen fluoride.

Workers should use appropriate personal protective clothing and equipment carefully selected, used, and maintained to be effective in preventing skin contact with HF. The selection of the appropriate personal protective equipment (e.g., gloves, sleeves, and encapsulating suits) should be based on the extent of the worker's potential exposure to HF. Nonvented, impact-resistant goggles should be worn when working with fumes, gases, or vapors. A face shield should be worn along with goggles when working with corrosive, highly irritating, or toxic substances.

Where the potential exists for exposure of over 3 ppm of HF, a Mine Safety and Health Administration/National Institute of Occupational Safety and Health (MSHA/NIOSH)-approved full-face piece respirator with a chemical cartridge specific for hydrogen fluoride should be used. Increased protection may be obtained from full-face piece powered air-purifying respirators.

Source: Medical Disability Advisor



Failure to Recover

If an individual fails to recover within the expected maximum duration period, the reader may wish to consider the following questions to better understand the specifics of an individual's medical case.

Regarding diagnosis:

  • Did individual present with symptoms consistent with toxic exposure?
  • Were urine and blood fluoride levels tested?
  • Is there a history of hydrogen fluoride exposure in the workplace?
  • Has individual recently worked in another organization where hydrogen fluoride exposure is higher?
  • Would individual benefit from consultation with an appropriate specialist?
  • Were other conditions with similar symptoms considered in the differential diagnosis?

Regarding treatment:

  • Was treatment appropriate for the type of exposure and severity of symptoms?
  • Was hospitalization required?

Regarding prognosis:

  • Was exposure mild or significant? What was the expected outcome?
  • Did individual suffer any complications associated with the toxic exposure?
  • Were complications addressed in the treatment plan?
  • Did individual have any conditions that may complicate treatment?
  • What was the expected outcome?

Source: Medical Disability Advisor



References

Cited

Watson, William A., et al. "2002 Annual Report of the American Association of Poison Control Centers Toxic Exposure Surveillance System." American Journal of Emergency Medicine 21 5 (2003): 353-421. MD Consult. Elsevier, Inc. 18 Oct. 2004 <http://home.mdconsult.com/>.

Wilkes, Garry. "Hydrofluoric Acid Burns." eMedicine. Eds. Edward A. Michelson, et al. 7 May. 2001. Medscape. 18 Oct. 2004 <http://emedicine.com/emerg/topic804.htm>.

Source: Medical Disability Advisor






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