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, Lead (Inorganic Compounds)


Related Terms

  • Lead Poisoning
  • Lead Toxicity
  • Plumbism

Differential Diagnosis

Specialists

  • Internal Medicine Physician
  • Medical Toxicologist
  • Neurologist
  • Pharmacologist
  • Preventive Medicine Specialist

Comorbid Conditions

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 will determine length of disability. Age and the general state of health and pre-existing disease will affect disability.
The effects of lead exposure may be worsened when CNS diseases and disorders are present, and may prolong the extent and length of disability.
The absorbed dose is the primary determinant of severity of toxic effects, and therefore the severity and duration of disability. The absorbed dose varies with environmental levels, routes of exposure (skin contact, inhalation, ingestion), and duration of exposure.

Medical Codes

ICD-9-CM:
984.0 - Toxic Effects of Lead and Its Compounds (Including Fumes), Inorganic Lead Compounds
984.1 - Toxic Effects of Lead and Its Compounds (Including Fumes), Organic Lead
984.8 - Toxic Effects of Lead and Its Compounds (Including Fumes), Other Lead Compounds
984.9 - Toxic Effects of Lead and Its Compounds (Including Fumes), Unspecified Lead Compound

Overview

Lead is the most prevalent environmental pollutant in the world, and lead toxicity can affect every system in the body, causing significant damage or death (Khan). Lead, a bluish gray metal widely distributed throughout the earth's crust, is used in many industrial applications. The most important uses of lead are in storage batteries, paints, ceramic glazes, solder (auto radiators) and ammunition. Lead can enter the body through the skin, lungs, and gastrointestinal tract. In adults, inhalation is the most common mechanism, especially in occupational settings. Ingestion is the most common route for childhood exposures. The degree to which lead is absorbed depends on the particle size (the smaller the particle, the more is absorbed) and the nutritional state and age of the individual. Once in the body, lead is distributed throughout all tissues. About 99% of all lead in the body binds to red blood cells. This lead remains in the blood about 25 to 40 days. Lead that is deposited in soft tissue remains for 40 or more days, but lead deposited in bone will remain for almost 30 years. Lead that is not retained in the body is excreted in urine and bile. Lead found in bullet fragments and shrapnel left in the body, especially in soft tissue, can leach into tissues causing long-term exposure.

Lead interferes with many metabolic processes in the body, including synthesis of the compound (hemoglobin) that allows red blood cells to carry oxygen to the cells and remove carbon dioxide. Lead also competes with calcium in bones, stunting skeletal growth in children. Lead can have severe effects on the nervous system, especially the brain. It is thought to interfere with the chemicals (neurotransmitters) that transmit of nerve impulses across synapses, and to reduce the effectiveness of the blood-brain barrier. Lead also interferes with some of the enzymes involved in protein synthesis, thus inhibiting cellular respiration. As a result, even exposure to low doses of lead in young, rapidly growing children stunts physical and mental development, and in adults causes widespread physical and mental changes.

Lead poisoning can be either immediate (acute) or long-term (chronic). Infants and children are especially sensitive to neurotoxic effects of lead, and they are more likely to experience acute poisonings than adults. Most acute poisonings occur through the ingestion of lead-containing substances such as paint commonly used before the mid-1970s. Most adults who experience acute lead poisoning are exposed by drinking illicitly produced liquor ("moonshine") that is distilled in old car radiators that contain lead. Food that has been stored in lead-contaminated containers (lead crystal, glazed ceramic and terracotta cookware or dishes), or water coming from a pipe or container soldered with lead can also be a source of lead toxicity.

Acute lead poisoning is a medical emergency characterized by abdominal colic, altered bowel habits, fatigue, and hemolytic anemia. Full-blown acute encephalopathy may occur. In milder cases, the only central nervous system symptoms may be headache or personality change. Liver damage, kidney damage (proximal tubular injury), and musculoskeletal pains may also occur. Reproductive capacity is reduced in both males and females, and may result in infertility.

Chronic poisoning occurs with exposure for months or years. Chronic lead poisoning is very difficult to diagnose, because symptoms are vague and similar to those of many other disorders. Symptoms of chronic lead exposure include arthralgias, headache, weakness, depression, loss of libido, impotence, and gastrointestinal complaints. Changes in personality, mood, memory, and cognitive abilities may occur. Nerve conduction and motor function may also be decreased, making it difficult to perform fine motor tasks. Endocrine function, renal function, and spermatogenesis may be abnormal. Late effects include chronic renal failure and brain dysfunction. Hypertension is more common in lead exposed populations. Symptoms become more frequent and severe as blood lead levels (BLL) increase.

Industries with particularly high potential exposures include construction, remodeling work, lead smelter mines, lead recovery from storage batteries, and radiator repair shops. Occupations at risk include plumbing, pipe fitting, auto repair, glass or plastic manufacturing, shipbuilding, printing, police work, steel welding, rubber product manufacturing, and firing range instruction.

Incidence and Prevalence: Lead levels over 10 mcg/dL in American children range from 1.5% to 36.7% depending primarily on the child's living environment; and, while the incidence of low-level chronic lead exposure in adults is difficult to determine, it is estimated that about 800,000 US workers have been exposed to a large amount of lead on the job (Habal). In 2003, 8,104 cases of lead poisoning were reported. Of these, only 1,066 occurred in adults, with the vast majority occurring in children under age six through accidental ingestions. Lead toxicity occurs worldwide, and occurs more frequently in developing countries. The incidence of lead exposure varies widely depending on the degree safety and environmental regulation and enforcement. Many countries still use lead as an anti-knock additive in gasoline, and continue to use lead in solder used in cans containing processed food. In other countries, exposure to industrial sources of lead is at best minimally regulated.

Source: Medical Disability Advisor



Causation and Known Risk Factors

It is estimated that 90% to 95% of lead toxicity in adults results from occupational exposure; males are affected more frequently than females due to a higher level of involvement in professions that are linked to lead exposure (Khan). Lead has many industrial applications, and more than 900 occupations have been associated with cases of lead poisoning (Marcus).

The risk of lead exposure is strongly related to socioeconomic factors; individuals of lower socioeconomic status who tend to live in houses built before 1950 where exposure to lead paint and lead water pipes are more likely have increased risk. As a result, black urban children are more likely to be exposed to lead than white suburban children (Marcus). Individuals exposed to automobile exhaust, lead paint, or lead-contaminated food containers also have an increased risk for lead toxicity.

Source: Medical Disability Advisor



Diagnosis

History: History is one of the most important factors in diagnosing chronic lead poisoning, since symptoms are often vague and diffuse. Individuals may complain of abdominal pain ranging from aches and general discomfort to severe cramping and pain (lead colic). Neurologic complaints can include headaches, dizziness, difficulty with memory, sleep disturbance, decreased strength, difficulty performing fine motor tasks, decreased sensation, and confusion. Individuals may also complain of muscle or joint aches, general fatigue, and decreased endurance.

Individuals may indicate they have a job or hobby that exposes them to lead—for example, welding, torching or braising old painted metal, renovating old houses with lead based paint, working with lead-containing ceramic glaze, or making stained glass. Some cosmetics (e.g., kohl) and folk remedies also contain lead, thus all aspects of an individual's history are important in making a diagnosis of lead exposure.

Physical exam: Most physical signs are not specific to lead toxicity, thus increasing the importance of a thorough history. However, the individual may have increased reflexes on physical exam. Neurological exam can reveal weakness of the arms and wrist drop caused by neuropathy. Elevated blood pressure, slowed heart rate, and mental status changes may occur. Extremely high blood lead levels (BLL) may cause stains on the inner cheek (buccal) surfaces, gray stains on the central retina, and edema of the optic disc (papilledema). However, most cases of chronic lead exposure produce few definitive signs on physical examination.

Tests: The definitive test for determining exposure to lead is a whole blood lead level test (BLL). Zinc protoporphyrin levels (ZPP) are commonly increased for several months follow lead exposure, though a variety of medical conditions can cause the same results. Renal function, liver function, and uric acid studies may also be done. Specialized x-ray tests can be used to estimate total body accumulation of lead. Tests may also be performed to rule out other possible diagnoses.

Source: Medical Disability Advisor



Treatment

Removal from lead exposure is essential in all cases of lead intoxication. Acute lead poisoning is a medical emergency. Individuals are hospitalized and given supportive care as needed. Individuals who have ingested lead may need gastric lavage or whole bowel irrigation to remove lead from the digestive system. Select symptomatic patients are also often treated with a chelating agent such as ethylene diamine tetra-acetic acid (EDTA), dimercaprol (British Anti-Lewisite [BAL]), or dimercaptosuccinic acid (DMSA). The chelating agent binds with lead in such a way that it can be excreted from the body.

Chronic lead poisoning is treated primarily through removing the individual from the source of exposure and through education to prevent re-exposure.

Source: Medical Disability Advisor



Prognosis

Optimal treatment may allow full recovery from lead exposure and its effects; however, exposure to even small amounts of lead can cause irreversible damage, especially in young, rapidly growing children. In adults, changes in mood and personality (e.g., increased aggression and depression) may remain even after exposure to lead is eliminated. With excellent medical treatment such as chelation therapy, death rates that would potentially be as high as 65% fall to less than 5%; but, individuals who survive lead encephalopathy may have neurological problems such as seizure disorders, cognitive impairments, and reduction in intelligence quotient (IQ) (Habal).

Source: Medical Disability Advisor



Rehabilitation

Individuals with central nervous system (CNS) damage from lead poisoning may require a range of rehabilitation services. The type, frequency, and duration of rehabilitation are contingent on the severity of symptoms.

Occupational therapy addresses any difficulty with activities of daily living. Individuals learn strategies for dressing, bathing, and meal preparation geared toward their particular functional limitations, as well as energy conservation techniques.

Physical therapy addresses mobility, strength, and balance. Individuals learn strategies for bed mobility and transferring from one surface to another. Individuals able to walk but who have decreased balance learn to use a cane, walker, or crutches to improve their gait pattern. Individuals may also be fitted with orthotic braces for the legs to help with muscular control. Individuals who cannot safely walk due to severe symptoms learn to use a wheelchair.

Speech therapy may be required for improved communication and eating. Individuals may perform resisted jaw, tongue, and lip movements. Because shallow respiration often occurs in individuals with this diagnosis, speech therapy may teach diaphragmatic breathing, vocal strengthening, and better sitting posture. To assist in the swallowing reflex, individuals begin eating semi-moist, pureed food that is easier to swallow and then progress to food rich in taste, smell, and texture. Individuals also learn to achieve sucking control and saliva production first by sucking on small ice chips and then progressing to resisted sucking of thick liquids through a straw.

Individuals may benefit from ongoing consultation with a psychologist or psychiatrist to cope with the loss of functional and physical abilities and with any depression that may occur. This may be particularly important for those individuals requiring the assistance of a caregiver.

Source: Medical Disability Advisor



Complications

Both acute and chronic lead exposure can cause long-term complications including decreased growth, decreased cognition, sterility, and renal failure.

Source: Medical Disability Advisor



Ability to Work (Return to Work Considerations)

The Occupational Safety and Health Administration (OSHA) and the National Institute of Occupational Safety and Health (NIOSH) 8-hour limit for occupational lead exposure is .050 milligram per cubic meter of air ("NIOSH Pocket Guide").

Lead exposure in the workplace is limited by law, and lead should be removed from the workplace to the greatest degree possible. If this is not possible, individuals with symptoms or elevated blood lead levels should be reassigned or transferred. Pregnant women should especially be made aware of the risks of lead exposure in the workplace. Parents should avoid bringing contaminated clothing home so as not to inadvertently expose their children.

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 have a clinical history and presenting symptoms consistent with the diagnosis of lead toxicity?
  • Is there a positive history of lead exposure in the workplace?
  • Could lead exposure occur outside the workplace, i.e., in the home, community, or recreational activities?
  • Has individual recently worked in another organization where lead exposure was higher?
  • Was the diagnosis confirmed with whole blood lead measurements?
  • Would individual benefit from a consultation with a specialist?
  • Were other conditions with similar symptoms considered in the differential diagnosis?

Regarding treatment:

  • Was the treatment appropriate for the type of exposure and severity of symptoms?
  • Did symptoms persist?
  • Were other more aggressive treatments, such as chelation therapy considered?
  • Were recommendations and instructions given to the individual regarding avoiding further exposure?
  • Has individual been compliant with the recommendations?
  • If not, are there barriers, such as poor understanding or employment issues, that contribute to poor compliance?

Regarding prognosis:

  • What was the expected outcome?
  • Did individual suffer any complications associated with the exposure?
  • Were the complications addressed in the treatment plan?
  • Does individual have any pre-existing conditions that influence response to treatment or ability to recover?
  • Could individual benefit from specific consultation depending on the organ system(s) involved?

Source: Medical Disability Advisor



References

Cited

"NIOSH Pocket Guide to Chemical Hazards: Lead." Centers for Disease Control and Prevention. 21 Mar. 2002. U.S. Department of Health and Human Services. 13 Jan. 2005 <http://www.cdc.gov/niosh/npg/npgd0368.html>.

Habal, Rania. "Toxicity, Lead." eMedicine. Eds. Lisa Kirkland, et al. 4 Oct. 2004. Medscape. 27 Oct. 2004 <http://emedicine.com/med/topic1269.htm>.

Khan, Ali Nawaz, et al. "Lead Poisoning." eMedicine. Eds. Beverly P. Wood, et al. 8 Dec. 2004. Medscape. 17 Jan. 2005 <http://emedicine.com/radio/topic386.htm>.

Marcus, Steven. "Toxicity, Lead." eMedicine. Eds. Mark Slabinski, et al. 4 Oct. 2004. Medscape. 13 Jan. 2005 <http://emedicine.com/emerg/topic293.htm>.

Source: Medical Disability Advisor






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