MODULE 9:OCCUPATIONAL HEALTH SERVICES

MODULE 9:OCCUPATIONAL HEALTH SERVICES:

Introduction

Definition:

Lead is a naturally occurring element that people have used almost since the beginning of civilization. Lead is bluish-gray in color and has no characteristic taste or smell. Lead has many different uses. A variety of human activities have spread lead widely throughout the environment, such as leaded gasoline. Efforts have been made to limit the use of lead containing products to minimize harmful effects on people and animals.

Exposure to high levels of lead can affect worker’s health and results in far more serious symptoms such as:

• Kidney damage
• Nerve and brain damage.

Lead and its compounds can enter the body in the following three ways:

· Inhalation

Lead can be breathed in when dust, fumes or vapour containing lead are in the air. Inhalation of these tiny lead particles is the most common source of exposure to lead at work.

· Ingestion

Lead particles such as powder or dust, can be ingested from contaminated clothing, hands, beard or moustache. These particles can also be ingested if food or beverage is contaminated with lead. Smoking contaminated cigarettes is particularly risky, because lead particles can be inhaled and ingested.

· Absorption

Tetra-ethyl and tetra-methyl lead, also known as lead alkyls, can enter the body through the skin.

Employees working in battery manufacturing plants may potentially be exposed to lead concentrations greater than the OSHA permissible exposure limit.
Battery Manufacturing is the process of producing lead-acid batteries, commonly used in automobiles, fork trucks, material handling, and standby power applications.

Medical Surveillances Activities for Workers Exposed to Lead:

The need for medical surveillance and the nature thereof is based on both the risk assessment and air monitoring results. It should be noted that persons exposed to lead alkyls should be under medical examination regardless of the levels of exposure. Medical Surveillance should be conducted by an Occupational Medicine Practitioner (OMP) who taking into account the nature of the work and the risks associated with it, should draft a structured surveillance programme. The initial medical examination should include any other biological tests necessary to determine the most appropriate work circumstances for the individual. For example the ability to wear a respirator and conditions that might aggravate a pre-existing medical disorders. The OMP may also request that certain medical investigations and tests, over and above those prescribed in the regulations, be carried out if he or she considers it to be in the interest of the health or safety of a person.

Biological monitoring

The only acceptable way of determining lead exposure via absorption through the digestive tract or the skin is by means of biological monitoring4. Absorption of lead through the skin only applies in the case of tetra- ethyl and tetra-methyl lead (both are known as lead alkyls), while ingestion through the digestive tract can be affected by airborne lead and non-airborne lead (or larger lead particles). The following tests are used to determine the level of exposure of a person to lead:

• Blood lead analysis

Blood lead concentration is the best available indicator of lead exposures. Normally the blood lead level should be checked every three months, especially if the employee is a woman capable of having children (procreation).

• Urine lead analysis

Alkyl lead compounds used as additives in motor fuels may be absorbed by inhalation, ingestion or skin contact. Absorbed organic lead is rapidly excreted in the urine, partially metabolised to inorganic lead. Blood lead levels are considered not to be adequate indicator of exposure to alkyl lead.

• Zinc Protoporphyrin (ZPP)

ZPP is a biological response test useful in assessing lead related biological effects. Lead exposure results in an increase in ZPP in the red blood cells and although there is no correlation between ZPP and blood lead at low exposures, it gives an estimate of exposure over the previous three months. It is recommended for screening purpose and is used as a biochemical indicator of lead exposure.

Medical surveillance is an essential part of an employer’s lead safety program and includes biological monitoring with periodic BLL testing, medical evaluation, and treatment if needed, and intervention to prevent or control identified exposure. The BLL is the best available measure of total exposure from both inhalation and ingestion. Biological monitoring provides feedback to the employer and worker about the efficacy of workplace controls, helps avoid surprises, and saves costs such as medical removal. Currently, under the OSHA standards, a worker must be included in a lead medical surveillance program if his/her airborne lead exposure is 30 μg/m³ (eight-hour time-weighted average) or higher for more than 30 days per year. The panel believes that the trigger for medical surveillance should not rely solely on air monitoring results; instead, workers should be included in a medical surveillance program whenever they are handling or disturbing materials with a significant lead content in a manner that could reasonably be expected to cause potentially harmful exposure through inhalation or ingestion. A medical surveillance program with increased frequency of BLL testing and early intervention for all lead-exposed workers is recommended to reduce health risks. The panel does not recommend routine ZPP testing as an early biomarker of lead toxicity; however, ZPP measurement is required by OSHA for certain levels of lead exposure. New employees and those newly assigned to lead work should have a preplacement lead medical examination and BLL test, followed by periodic BLL testing, blood pressure measurement, and health status review. Monthly BLL testing is recommended for the first three months of employment for an initial assessment of the adequacy of exposure control measures. Subsequently, testing frequency can be reduced to every six months as long as BLLs remain below 10 μg/dL (0.48 μmol/L). Any increase in BLL of 5 μg/dL (0.24 μmol/L) or greater should be addressed by re-examining control measures in place to see where improvements should be made and by increasing BLL monitoring if needed. If the task assignment changes to work with significantly higher exposures, the initial BLL testing schedule of monthly tests for the first three months at this task should be repeated. The above schedule for BLL testing may be inadequate for certain situations where the exposures are very high and/or highly variable. In these situations, the BLL testing schedule should be tailored to address the special risks of different types of work and exposures. For example, a construction worker may have very high, intermittent exposures in contrast to someone working in a battery plant or other general industry setting with significant exposures but less day-to-day variability. Employees assigned to tasks where exposures are extremely high (e.g., abrasive blasting) should be tested more frequently than as recommended above, at least monthly. In general, it is a good idea to do BLL testing at peak exposures to assess controls and, specifically for the construction trades, to test pre-, mid-, and post-job. Because of the significant reduction of lead in the general environment, new workers enter lead jobs with very low BLLs while others who have worked with lead often have much higher BLLs and body burdens. With increased biological monitoring frequency to ensure that low BLLs are maintained, it is possible that some workers with lead-related health risks may be able to work safely in a lead-exposed environment. All lead-exposed workers should receive education about the health effects of lead and prevention information from the clinician and the employer, and they should be provided necessary protections including protective clothing, clean eating areas, and hygiene measures such as wash-up facilities and/or showers to prevent both ingestion of lead and take-home exposures.

Chelation Therapy:

Primary management for adult lead poisoning is identification of the lead source and cessation of exposure. In adults, chelation therapy generally should be reserved for individuals with high BLLs and/or significant symptoms or signs of toxicity. There is no evidence-based guidance in this regard because of lack of appropriate studies. Based upon the clinical experience and judgment of panel members, the following general recommendations concerning chelation are offered: chelation therapy is recommended for adults with BLLs 100 μg/dL (4.83 μmol/L) or greater, can be strongly considered for BLLs 80 to 99 μg/dL (3.86-4.78 μmol/L), and possibly considered for BLLs between 50 and 79 μg/dL (2.41-3.81 μmol/L) in the presence of lead-related symptoms. BLLs greater than 100 μg/dL (4.83 μmol/L) almost always warrant chelation as they are usually associated with significant symptoms and may be associated with an incipient risk of encephalopathy or seizures. These are general recommendations and clinicians may vary appropriately from these recommendations depending upon circumstances. Adults with a very high BLL (e.g., 90 μg/dL (4.34 μmol/L)) may remain asymptomatic. Oral chelation has largely supplanted parenteral agents. Chelation therapy relies on enhancing renal excretion, and remobilization of lead from other body stores may occur. On a population basis it is important to reduce fetal exposure to lead, and maternal lead levels less than 5 μg/dL are optimal. However, laboratory measures are not absolutely precise, and clinical judgment is needed in every patient encounter. Chelation should be used during pregnancy ONLY to protect the life and health of the mother and ONLY if the potential benefit to the mother justifies the potential risk to the fetus. This decision will need to be made on a case by case basis by the attending physician. Because of the increase in lead mobilized from maternal bone during pregnancy, clinicians should be aware that maternal blood lead levels may exhibit an upward trend in the second and third trimesters even in the absence of further exposure. Women with a history of long-term lead exposure or prior elevated BLL's should be monitored regularly during pregnancy for BLL elevation. If the occupational history or clinical evaluation suggests elevated bone lead stores, clinicians may wish to counsel patients on delaying conception until the risk of mobilization of lead from bone depots has been reduced. Prophylactic chelation therapy of lead-exposed workers, to prevent elevated BLLs or to routinely lower BLLs to pre-designated concentrations believed to be “safe,” is prohibited by OSHA. Non-traditional uses of chelation therapy are not advised. There is no established basis to initiate chelation based on results of hair analysis or, in most cases, urine lead levels nor for chelation of asymptomatic individuals with low blood lead concentrations. Chelation should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Breast feeding during chelation therapy is not recommended. The effect of chelating agents on the fetus and newborn is unknown.

Pregnancy and Breast Feeding Concerns

Prevention of fetal and postnatal lead exposure of breastfed infants requires identification and control of sources of environmental and occupational lead exposures (both endogenous and exogenous) for pregnant and lactating women. The CDC has established 10 μg/dL (0.48 μmol/L) as a BLL of concern in children (CDC 2002). Because fetal blood contains approximately 80% of the blood lead concentration of the mother, and because of the risk of spontaneous abortion, the panel’s recommendation is that the mother’s BLL should be kept below 5 μg/dL (0.24 μmol/L) from the time of conception through pregnancy. For women with a history of lead exposure, calcium supplementation during pregnancy may be especially important and may thus minimize release of lead from bone stores and subsequent fetal lead exposure. In a recent prospective study, umbilical cord BLL and maternal bone lead measured shortly postpartum were independent risk factors for impaired mental development of the infants assessed at 24 months of age, even after controlling for contemporaneous BLL (Gomaa et al. 2002). Long-term prospective studies suggest that the adverse neurodevelopmental effects of prenatal lead exposure may not persist into adolescence if early postnatal exposure falls to background levels (Bellinger et al. 1990, 1992; Tong et al. 1996). However, maternal BLL measured during pregnancy has been associated with alterations in brainstem auditory response at in the offspring at age five (Rothenberg et al. 2000), and in retinal response at age 10 (Rothenberg et al. 2002b).

Lead does not concentrate in breast milk because it does not bind to nor dissolve in fat; thus, levels of lead are generally higher in a mother’s blood than in her milk. Lead in human breast milk appears to be well-absorbed by breast fed infants. Nevertheless, breast feeding should be encouraged in most situations since the benefits generally outweigh the negatives. Decisions relating to lactating women with evidence of very high lead exposure should be made on an individual basis. If elevated maternal blood lead is suspected or demonstrated, the source(s) of lead exposure in the mother’s diet, home, and work environment should be identified and mitigated. Also, the clinician should monitor infant BLLs during the early weeks of breast feeding. Only upon detection and elimination of all other suspected lead sources without corresponding reduction of infant BLL should cessation of breast feeding be advised.

Retained Bullet

Gunshot injuries to the head, face, and neck may be associated with swallowed bullets, fragments, or pellets, which result in a rapid increase in blood lead in the first days following injury. After detection of bullet fragments in the gut with X-rays, efforts to promote gastrointestinal decontamination may result in a gradual reduction of blood lead over the following weeks. Retained bullets or fragments, particularly those in joint spaces, are risk factors for elevated BLL after injury. Decisions to remove bullet fragments imbedded in tissue should be made in consultation between the treating physician and the surgeon. Individuals with retained bullets should receive baseline and periodic blood lead testing to monitor their lead status. Follow-up blood lead levels may not be needed if the bullets are in muscle tissue and physicians are sure the lead fragments have not migrated from muscle into tissues more likely to allow lead uptake.

Employer should ensure that they act on the decision of the OMP and not allow employees with blood level exceeding 60μg/100ml or 150μg/l in case of urinary lead, to work in an environment where they will be exposed to lead. Separate approach is adopted for women who are of childbearing age (Capable of procreation) when measuring lead concentration because lead can be passed on to the unborn child. Occupational exposure to lead has been associated with decreased fertility, spontaneous abortion, stillbirths, and increased infant mortality. Lead readily passes the placenta and accumulates in the fetus and there is strong evidence that a mother’s lead burden can cause serious effects on cognitive development of her child. Women should therefore be removed from the workplace where they are exposed to lead as soon as it is confirmed that they are pregnant or when their blood lead exceeds 40μg/100ml or 75 μg/l in case of urinary lead.

Personal Protective Equipment and Facilities

Employers must provide effective personal protective equipment and facilities free of charge. The equipment must also be properly selected, maintained, cleaned, undamaged and properly used. Some manufacturers of respirators give specific instructions in this regard.

Personal Protective Clothing

All employees who are exposed to lead must be provided with protective clothing. The protective clothing issued to employees who are exposed to tetra-alkyl lead, which is absorbed through the skin, must be made of impermeable material, to prevent skin contact and thus absorption.

Respiratory Protective Equipment

All employees in respirator zones, and any other employees who by the nature of their work may be exposed to greater than the OEL for lead, must be provided with respirators. Only respirators that have been approved /homologated by the South African Bureau of Standard (SABS) may be used. When selecting a respirator, the following must be kept in mind:

· The concentration of airborne lead

· The duration of exposure

· The exposure limit for the lead

· The safety factor of respiratory

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