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, Organophosphate and Carbamate Pesticides


Related Terms

  • Carbaryl Exposure
  • Dichlorvos Exposure
  • Malathion Exposure
  • Parathion Exposure
  • Phorate Exposure
  • Phosdrin Exposure

Differential Diagnosis

Specialists

  • Medical Toxicologist
  • Pharmacologist
  • Preventive Medicine Specialist

Factors Influencing Duration

Absorbed dose is the primary determinant of the severity of toxic effects and therefore the severity and duration of disability. Absorbed dose depends on environmental levels, routes of exposure (skin contact, inhalation, ingestion), and duration of exposure.
The period of observation can vary from several hours for the asymptomatic individual to at least 48 hours of hospitalization in symptomatic cases. Recovery periods can vary from a few days to almost a year.
Other factors influencing disability include pre-existing disease, age, pregnancy, and allergy, all of which affect individual susceptibility to the toxic effect of chemical exposures and the individual's ability to recover functional capacity and return to work. Psychological and emotional factors may also play a role in the extent and duration of disability.

Medical Codes

ICD-9-CM:
989.3 - Toxic Effects, Organophosphate and Carbamate Pesticides

Overview

Organophosphate and carbamate compounds are found in a wide variety of insecticide preparations marketed for home, garden, and agricultural use. Since there are so many formulations with different trade names, identification of the active ingredients may be difficult without the help of a Poison Control Center.

Over 80% of the pesticide poisonings in the US are caused by organophosphate and carbamate pesticides. These compounds inhibit acetylcholinesterase, an enzyme critical to the control of nerve impulse transmission from one cell to another. When the enzyme is inhibited, there is overstimulation and then paralysis of the secondary cell. The character, duration, and degree of the resulting physiologic effect are directly related to the amount and rate of enzyme inhibition at certain receptor sites in the central and peripheral nervous systems. Some critical amount of enzyme must be inactivated before the signs and symptoms of poisoning are evident.

The use of organophosphate and carbamate compounds has increased markedly since the 1970s, when many of the organochlorine insecticides such as DDT were banned. In contrast to the organochlorines, organophosphate and carbamate insecticides degrade rapidly in the environment and do not accumulate or concentrate in the food chain. Thus they have less potential for chronic health effects or environmental contamination. However, organophosphate and carbamate compounds have a greater potential for acute toxicity than the organochlorines, although there is a wide spectrum of potency for acute toxicity in humans among these chemicals. Carbamate compounds are less toxic than organophosphates, but all present the risk of acute and subacute toxicity.

Many of the toxic "nerve agents" used by the military are similar organophosphate compounds. Exposure to organophosphates and carbamates produces a characteristic, treatable syndrome in humans. Its recognition and timely intervention are of great importance to emergency physicians and affected individuals.

Agricultural exposure is the most common site of organophosphate and carbamate poisoning. Anyone involved in the manufacture, formulation, transportation, or application of these chemicals is at risk. Most organophosphate and carbamate insecticides are used for crop spraying in commercial agriculture. Approximately 75% of all insecticides are used on three crops: cotton, corn, and soybeans. Poisoning has often occurred among harvest workers who enter a field too soon after crops have been treated. Other occupations at risk include pest control workers, custodial workers, veterinarians, and pet groomers. Accidental exposure of the unsuspecting public can occur near sprayed fields due to wind shifts. Intentional ingestion in a suicide or homicide attempt is not uncommon. Most occupational exposures occur from skin absorption, although inhalation is possible during pesticide manufacture, formulation, and application. Although a few cases of mild poisoning from dietary exposure have been reported, hazard to consumers from surface contamination appears to be minimal.

Incidence and Prevalence: According to the 2002 annual report of the American Association of Poison Control Centers, there were 3,022 exposures to carbamates, with no reported deaths. The same report cited 8,031 exposures to organophosphates, with 4 reported deaths in the US, a substantial decrease since 1998 (Watson 353). However, it is estimated that only 1% of field worker illness from pesticide exposure is reported (Slapper). A significant number of children are accidentally exposed to these chemicals and tend to have more severe symptoms because of their size and the relative ease with which they absorb the chemicals. Organophosphate and carbamate poisonings occur worldwide, with higher incidences in less developed countries because of poor education about toxicity and less regulatory oversight in their manufacture and use. Intentional exposure (suicide and homicide) to these compounds is also more common in developing countries.

Source: Medical Disability Advisor



Causation and Known Risk Factors

There is no predisposition to poisoning by organophosphates or carbamates based on age, sex, or race. However, because of the demographics of agricultural, manufacturing, and pest control workers, most individuals who present with symptoms are men between the ages of 15 and 45.

Source: Medical Disability Advisor



Diagnosis

History: Individuals may complain of mild flu-like symptoms, including headache, muscle cramps, fatigue, nausea, vomiting, and diarrhea. They often report exposure to pesticides in agricultural or manufacturing environments. Because of the nonspecific nature of symptoms in mild poisonings, the history of exposure is an important diagnostic tool.

In general, the onset of symptoms is more rapid after respiratory exposure than ingestion or skin absorption, ranging from minutes to hours. However, significant variation in onset of symptoms occurs, depending on the specific agent and its metabolism, as well as individual variation in response. Delayed onset of 24 to 48 hours can occur.

Physical exam: Individuals with mild poisoning present with weakness, headache, and gastrointestinal upsets. With more severe poisoning, characteristic findings include small pupils (miosis), excessive salivation, respiratory distress, hyperactive bowel sounds, hypertension, generalized muscle weakness, tremor, convulsions, altered consciousness, and coma.

Two syndromes are recognized. In the immediate syndrome, symptoms appear relatively soon after exposure. In organophosphate-induced delayed syndrome, symptoms appear at least 10 days after a single acute exposure or after months of cumulative small exposures (Dyro).

Tests: Specific laboratory diagnosis of organophosphate/carbamate poisoning is possible. Acetylcholinesterase (AChE) activity can be measured in the serum and red blood cells (RBC). The red cell measurement is more specific, as the serum level may be decreased with liver disease or chronic inflammation from any cause. Clinical symptoms generally appear after the RBC activity has been depressed by 50% of baseline, but the rate of decline is more important than the absolute level. Some individuals may have mild symptoms when the AChE activity is depressed by 30% to 50%. AChE levels are not particularly useful in following recovery after acute poisoning (clinical observation is the best guide), but they are essential in the biologic monitoring of occupationally exposed workers.

Supportive laboratory tests include CBC, arterial blood gas (ABG), serum electrolytes, BUN, creatine, and serum glucose. A chest x-ray may be useful in determining the presence of pulmonary edema, and an electrocardiogram (ECG) in identifying heart dysrhythmias.

Source: Medical Disability Advisor



Treatment

There are four steps in the effective treatment of organophosphate/carbamate poisoning. First, emergency personnel should support respiration with suction, oxygen, and intubation as indicated.

Second, medical workers should decontaminate the individual by removing clothing and washing the skin, hair, and fingernails with soap and water (mild intoxication has progressed to life-threatening disease because of continued absorption from clothes or skin). If ingestion is the route of exposure, induced vomiting (only before onset of significant symptoms), gastric lavage, and administration of charcoal/saline cathartic may be indicated. Health care personnel should be careful to avoid contamination from the patient.

Third, specific antidotes may be administered. Poisoning with these chemicals is one of the few situations in which antidote therapy can be lifesaving. Two different drugs are effective and can be used in combination: atropine and 2-PAM (pralidoxime). Massive doses of atropine may be required and may help confirm the diagnosis. The use of 50 mg in 24 hours is not unusual. The goal is to titrate the dose versus the individual's signs until a mild "atropinization" is observed (flushing of the skin, dilated pupils, drying of secretions, and rapid heartbeat). Use of 2-PAM (pralidoxime) is indicated in all significant organophosphate poisonings (it is usually unnecessary in cases of carbamate poisoning). To be effective, it must be given within the first 12 to 24 hours after exposure.

Fourth, continued observation of the poisoned individual is vital. Symptoms may progress during the first 24 to 48 hours due to delayed absorption from the skin or GI tract.

Source: Medical Disability Advisor



Prognosis

Prompt and aggressive treatment usually leads to complete recovery within 10 days.

Long-term follow-up evaluation of workers with acute toxicity and workers with repeated low-dose exposures has shown evidence of persistent neuro-psychologic impairment with deficits of memory, concentration, and brain-wave abnormalities, as well as emotional disturbances such as irritability, anxiety, and depression. The degree to which these abnormalities directly results from organophosphate toxicity or from a psychologic reaction to the poisoning episode is difficult to resolve in individual cases, but they may result from delayed treatment.

Death, although rare, is usually secondary to respiratory failure from increased bronchial secretions, bronchospasm, muscle paralysis, and central nervous system depression and usually occurs within the first 24 hours when severe toxicity goes untreated.

Source: Medical Disability Advisor



Complications

Immediate complications of severe toxicity include pulmonary congestion, bronchospasm, muscle paralysis, seizures, and central nervous system depression. Long-term complications may include weakness, chronic pain, fatigue, irritability, memory impairment, depression, and psychosis.

Source: Medical Disability Advisor



Ability to Work (Return to Work Considerations)

The Occupational Safety and Health Administration's (OSHA) recommended airborne permissible exposure limits (PEL) range from less than 0.1 to 15 mg/cubic meter, and recommended exposure limits for skin as a time-weighted average (TWA) range from less than 0.1 to 15 mg/cubic meter over an 8-hour work shift.

The National Institute of Occupational Safety and Health's (NIOSH) recommended airborne exposure limits (REL) range from less than 1.0 to 15 mg/cubic meter, and skin exposure limits as a time-weighted average (TWA) range from less than 0.05 to 10 mg/cubic meter over an 10-hour work shift. OSHA and NIOSH exposure limits for each specific chemical are available in print or on line.

The American Conference of Governmental Industrial Hygienists' (ACGIH) recommended airborne exposure values range from 0.9 to 10 mg/cubic meter for an 8-hour work shift.

Immediately Dangerous to Life or Health (IDLH) values range from 10 to 250 mg/cubic meter.

Where organophosphates and carbamates are manufactured, stored, formulated, or transported, workers should wear protective work clothing and wash thoroughly immediately after exposure and at the end of each work shift. Hazard and warning information should be posted in the work area. In addition, as part of an ongoing education and training effort, all information on the health and safety hazards of the organophosphates and carbamates should be communicated to potentially exposed workers.

Skin contact with organophosphates and carbamates should be avoided. Protective gloves and clothing should be worn. Safety equipment suppliers and manufacturers can provide recommendations on the most protective glove/clothing material for the particular operation.

All protective clothing (suits, gloves, footwear, and headgear) should be clean, available each day, and put on before work.

Eye protection should include at least goggles and face shields when needed. Eye protection is provided where a supplied air respirator is used. Where the potential exists for exposures over the listed values, a OSHA/NIOSH-approved supplied-air respirator with a full face piece operated in the positive pressure mode or with a full face piece and hood should be used. A helmet in the continuous flow mode or the use of a OSHA/NIOSH-approved self-contained breathing apparatus with a full face piece operated in pressure-demand or other positive pressure mode may be needed.

Workers who apply pesticides for pest control should wear the protective clothing while engaged in their work. The fabric will vary, depending upon the toxicity and form of the pesticide. Shirts, trousers, hats, and chemical-resistant footwear, as well as chemical-resistant gloves, are the minimum. If highly toxic materials are being applied, breathing apparatus and full-body chemically resistant clothing, gloves, and boots may be needed.

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:

  • Has diagnosis of toxic effects of organophosphate and carbamate pesticides been confirmed?
  • Is there a history of organophosphate or carbamate exposure in the workplace?
  • Is the clinical illness, including history, physical examination, and laboratory findings, consistent with other case descriptions?
  • Are the whole blood and urine levels of the organophosphate or carbamate metabolites and cholinesterase at or near the normal value?
  • Is the timing between exposure and clinical onset compatible with the known biologic facts about the hazard?
  • Is the exposure dose within the range of doses believed to cause such effects?
  • Has individual experienced any complications related to the toxic effects of organophosphate and carbamate pesticides?
  • Is individual pregnant, or are there special attributes of the particular individual that make it more or less likely that he or she would be more affected by the toxins?

Regarding treatment:

  • Were diagnosis and treatment prompt and adequate?
  • Have symptoms resolved?

Regarding prognosis:

  • To what extent is function impaired?
  • Has individual recently worked in another organization where organophosphate or carbamate exposure is higher?
  • Could organophosphate or carbamate exposure be occurring outside the workplace; i.e., in the home, in the community, or in recreational activities?
  • Are there additional lifestyle or behavioral factors that may potentially contribute to this condition?

Source: Medical Disability Advisor



References

Cited

Dyro, Frances M. "Organophosphates." eMedicine. Eds. Jonathan S. Rutchik, et al. 14 May. 2003. Medscape. 26 Oct. 2004 <http://emedicine.com/neuro/topic286.htm>.

Slapper, Debra. "Toxicity, Organophosphate and Carbamate." eMedicine. Eds. Dana A. Stearns, et al. 5 Aug. 2004. Medscape. 26 Oct. 2004 <http://emedicine.com/emerg/topic346.htm>.

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.

Source: Medical Disability Advisor






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