Toxicology

 

4 Abstract

The purpose of this report is to identify some key issues in the workplace that can affect employee health and safety. Duties remain on the person conducting a business or undertaking to provide a safe work environment. This should occur through systems of work, effective design of work and occupational health and safety training. There must be identification of the hazards and subsequent control measures implemented. Ideally, designers will eliminate the risk to workers, through work practices and engineering controls and verify this through biological monitoring.

 

4.1 Occupational Disease in the Workplace

Occupational health is about the effect of the workplace on health and the impact of health on the workplace. It can play a role in assisting employers care for and understand the needs of their employees, enabling businesses to reduce sickness absence levels and optimise employee performance and efficiency (Commonwealth of Australia 2008). Occupational diseases can be unlike occupational safety, where there can be a clear cause and effect relationship between the incident and the health outcome. “Most occupational diseases are multifactorial in nature” (Kimber 2010 p5), with work place exposures to hazards contributing one essential part of a workplace risk matrix.  Occupational diseases such as cancers can have long latency periods and the relationship between cause and effect can be difficult to determine.  These factors can lead to significant lagging and under reporting of occupational disease through the system (Kimber 2010) therefore, making control measures difficult to implement and evaluate. These occupational diseases then maybe imparted to unaware staff in the workplace to be suffered some years later.

Eight occupational disease groups have been identified to be possible in some workplaces. These diseases should be identified, assessed, controlled and then monitored, to limit occupational disease in the workforce. These occupational diseases groups are:

  • Musculoskeletal disorders
  • Mental disorders
  • Noise-induced hearing loss
  • Infectious and parasitic diseases
  • Respiratory diseases
  • Contact dermatitis
  • Cardiovascular diseases
  • Occupational cancers

4.2 Risk Management

A risk register may be used to record the hazards that may possible on the site. Responsible person/persons should identify all the hazards that may have a negative impact on stakeholder’s health and safety and enter these into the register. The process is of identification of the hazard, assessment of the risk, control of the risk and then review/monitor the process. Although there are multitudes of hazards possible in the workplace, for the purpose of this report the risks associated with lead processing will be the core theme.

“Engineering controls are the single most effective means of control” (National Occupational Safety and Health Commission 2001). The purpose of control measures is to prevent, or where that is not possible, control exposure to lead-containing hazardous substances so as to minimise stakeholder exposure to lead.  So far as reasonably practicable, the prevention or control of lead containing hazardous substances should be secured by measures other than the use of personal protective equipment.  Control measures should be implemented in accordance with the hierarchy of controls (National Occupational Safety and Health Commission 2001) listed below.

  • Elimination
  • Substitution
  • Isolation
  • Engineering controls
  • Administration controls
  • Personal protective equipment

  The effectiveness of control measures should be assessed by:

  • Static atmospheric monitoring
  • Personal lead in air monitoring, (in the breathing zone of the employee)
  • Biological monitoring of employees in lead-risk jobs (Codes of Practice 1994)

These measures should be for guidance on providing and maintaining a safe workplace. Work processes should be continually looked at, to improve procedures and reduce the lead exposure levels. Compliance with exposure standards does not preclude an organization from further minimizing exposure levels. “Exposure standards do not represent no effects levels at which every employee can be guaranteed protection” as stated in the Codes of Practice (1994 p53). Therefore, it is an ideal practice to keep the level of exposure to lead as low as is practicable.

4.3 Identification

A modern workplace must identify the hazards that are relevant to its operation. Work place health and safety legislation imposes duties on the person conducting a business or undertaking (PCBU), to provide and maintain a working environment that is safe and without risks to health. The PCBU is also to monitor the health of their workers and conditions of the workplace under their management and control to prevent injury or illness (Policy, Guide to the Work Health and Safety Act 2011 Queensland). Typically the organization through analysis should identify the occupational disease groups which their workforce may be exposed to and apply risk minimization practices. The first step in the process would be hazard identification of substances and or work practices that may expose workers to a risk which will have an adverse effect on the workers’ health.

Hazard identification involves collecting and evaluating data on the types of health effects or disease that may be produced by e.g. chemicals under which injury or illness may be evident, Van Leeuwen & Vermeir (2007). Furthermore, a toxic chemical that is hazardous to human health does not constitute a risk, unless workers are exposure to the chemical. Hazards are not confined to only a particular section of a business, for example; contaminated dusts can be carried on work boots to areas of the business and may constitute a threat to unsuspecting workers, e.g., floor mats at the medical centre (Steel 1985). Only experienced persons should be involved in hazard identification. Ongoing training of these staffs is essential to promote and maintain a healthy workplace.

4.4 Registers

A register provides a listing of all hazardous substances which may be used or produced in the workplace.  Employers and employees should use the register as a source of information and as a tool to manage substances used at work. Employees with the potential for exposure to lead-containing hazardous substances, employee representatives, emergency services and local authorities should have access to the registers (Workcover 2012). All chemicals that are  in the workplace should have a material safety data sheet (MSDS) supplied by the manufacturer or supplier. This chemical should then be entered in to the hazardous goods register as per the OHS&W Regulations (1995).

Step One - Record the details:

  • Write down in the register all the hazardous substances on the site including  decanted substances
  • Make sure MSDS are available for every hazardous substance kept and/or used on site
  • Conduct a risk assessment (Note: Clause 168 of the (Occupational Health Safety Regulation 2001) places a duty on employers to record the results of risk assessment relating to the use of hazardous substances)

Step Two - Check the details:

  • Person of authority (Manager) to ensure that the hazardous substance   register is  maintained

Step Three - Inform staff:

  • All staff that have contact with hazardous substances must be trained  in their correct use, storage and access to a MSDS (Workcover 2012)

 

The reaction of the body from exposure to substances depends on the nature of the substance, “the health effects it can cause and the amount of the substance or mixture absorbed by the body” (Craigie 2009 p5). The extent to which the employee is exposed “depends on the concentration of the substance or mixture in the air, the amount of time the employee is exposed and the effectiveness of controls” (Craigie 2009 p5).  Exposures to toxic fumes or dusts outside the set parameters can cause immediate, acute health effects.

4.5 Issue on the Worksite

An issue for the employee/contractor on the site is to comply with all specific workplace policies, procedures and directions. The PCBU must control the risks associated to the hazards specific to operations (lead process) so that no persons are exposed to an unacceptable risk.

  • Lead should not be spread outside lead processing areas, resulting in exposure to lead of: (a) employees not engaged in the lead process, (b) other persons, (c) the general public in the surrounding area  (Codes of Practice 1994)

Information regarding all lead-containing hazardous substances should be available to all stakeholders. This information includes:

  • The register of lead-containing hazardous substances used in the workplace
  • Material Safety Data Sheets compiled in accordance with the National Commission's Code of Practice for Preparation of Material Safety Data Sheets (Codes of Practice 1994)
  • Reports prepared as a result of workplace assessment
  • The results of atmospheric monitoring
  • The results of health surveillance programs provided that medical confidentiality are maintained

4.6 Monitoring of the Site

Health monitoring is required for stakeholders engaged in performing lead-risk work. Lead-risk work is defined as work carried out in a lead process that is likely to cause the blood lead level of staff carrying out the works or exposed to inorganic lead contaminants to exceed:

  • For a female of reproductive capacity – 10 μg/dL (0.48μmol/L)
  • In any other cases- 30 μg/dL (1.45μmol/L) Workplace Health & Safety Queensland (2012)

Where the monitoring of airborne contaminants is used to determine an employee’s exposure to lead, the monitoring must be conducted in the breathing zone of the person, via personal monitoring (Craigie 2009). Air samples taken in  pre-determined places in the work environment ‘static samples’ cannot provide individual personal exposure data, and should be only used to evaluate process control measures. “In some cases, fixed continuous monitors may also be used to provide early warning of leaks or other contaminating sources which could eventually lead to worker exposures above the exposure standard” (Craigie 2009 p8). The monitoring programme should also take into account the nature and extent of work, sampling and analysis errors. Analysis of samples taken in the workplace should be carried out by a National Association of Testing Authorities (NATA) accredited laboratory. The results of monitoring must be kept for a period of 30 years from the date of the last entry made in the records (Workplace Health & Safety Queensland 2012).

 The  process of medical screening and monitoring can play a vital role in the occupational health  program, however, it also has its limitations. A concern with this is that these screening programmes may be used by employers as a cheaper alternative to environmental monitoring and engineering controls  (Quinlan & Bohle 1991). Ideally, medical screening should be used as a secondary process, to confirm the integrity of the work practices and controls in place to maintain the health of the workers.

4.7 Effects of Exposure to Lead

Some possible effects of lead exposure are listed below:

  • Nervous system – CNS acute encephalopathy- memory loss, poor concentration, depression, headache, tremor
  • Chronic encephalopathy– psychomotor disturbance, impaired cognitive function
  • Kidney – progressive deterioration of renal function often with hypertension
  • Gastrointestinal – anorexia, epigastria discomfort, colic, constipation or diarrhoea
  • Reproductive – effects on sperm morphology and count, some adverse pregnancy outcomes have been attributed to lead (Workplace Health & Safety Queensland 2012)

4.8 Routes of Exposure

The four principal routes for exposure to hazardous materials are ingestion, dermal absorption, inhalation and injection (Griffin1989). Duties remain on the PCBU, to provide a safe workplace and training for stakeholders when they come into the business. This provision, should limit exposure if all persons work collaboratively towards a common goal.

 For example, cleaning of areas which may be contaminated with lead should be done as frequently as is necessary to ensure cleanliness and the removal of lead deposits, reducing the risk of inhalation and ingestion of lead. In particular, the following should be cleaned at the minimum frequency (a)floors and workbenches at least once per day (b)washing and changing rooms and facilities for eating and drinking should be washed, cleaned at least once per day (National Occupational Safety and Health Commission 2001). These are examples of requirements from the National Code of Practice for the control and safe use of inorganic lead at work [NOHSC: 2015(1994)].

4.9 Removal from Lead-Risk Work

Exposure standards represent the airborne concentration of a specific substance or mixture that must not be exceeded. There are three types of exposure standards: (National Standards, Codes of Practice and related guidance 1995)

  • 8-hour time-weighted average
  • Peak limitation
  • Short term exposure limit

Standards for exposures are based on the airborne concentrations of individual substances, in this case lead, which according to current knowledge, should not cause adverse health effects nor cause undue discomfort to nearly all workers.

 

Strenuous work increases lung ventilation, thereby increasing the uptake of airborne contaminants. Similarly, heavy physical work under adverse climatic conditions, such as excessive humidity or heat, or work at high altitudes, may lead to an increased uptake of contaminants. “It is of particular importance, that any evaluation of the working environment considers the lung ventilation rate where there is a significant airborne concentration of contaminant” (National Standards, Codes of Practice and related guidance 1995 p8). Designers should consider these factors when procedures are written so that workers are protected at all times.

Air monitoring is necessary to determine the risk; any subsequent introduction of controls should be based on comparing results of monitoring with the exposure standard. Compliance with an exposure standard can be demonstrated only when the exposure of individual workers or groups of workers are known, with an accepted degree of certainty, to be below the exposure standard (Craigie 2009). The prescribed limits are:

  • Females not of reproductive capacity and males 50 μg/dL (2.42μmol/L)
  • Females of reproductive capacity 20 μg/dL (0.97μmol/L)
  • Females pregnant or breastfeeding 15 μg/dL (0.72μmol/L) (Workplace Health & Safety Queensland 2012)

If through the process of biological monitoring staff are found to exceed the prescribed limits, these workers must be removed from the site and health professionals be engaged for the rehabilitation of the worker. Biological monitoring should take place every six months, or more frequently, depending on the results of the blood-lead count. The PCBU must provide employees with results and employee representatives with the aggregate results of lead exposure assessments of employees in the designated work group.  The employers should consult with employees and employee representatives about actions that are undertaken in minimising the risk of lead exposure (National Occupational Safety and Health Commission 2001).

4.10 Summary of Toxicology

The acute effects of over-exposures to inorganic lead can be characterised by “anaemia, abdominal colic, peripheral neuropathy (extensor weakness, wrist/ankle drop), and central neuropathy with toxic encephalopathy, nephropathy, and sterility. Tremors, stupor, intractable seizures and coma may result from very severe poisoning” (Workplace Health & Safety Queensland 2012 p7). In adults, acute encephalopathy usually occurs only at blood levels above 7.5 μmol.

In some settings, lead poisoning is a chronic disease with an incremental accumulation of toxins. “Workers with lower-level, persistent or recurrent exposure to lead may develop non-specific symptoms such as anorexia, indigestion, myalgia, fatigue, irritability and headaches” (Workplace Health & Safety Queensland 2012 p7). There can be variation from one person to another in the level at which symptoms occur: “some lead workers appear symptom-free at blood levels of 5μmol/L, while others will suffer anorexia and abdominal discomfort at levels of 3μmol/L” (Workplace Health & Safety Queensland 2012 p7). Once absorbed, lead becomes widely distributed in the body and interacts with a number of enzymes, “of which the enzymes associated with haem synthesis appear to be the most sensitive” (Workplace Health & Safety Queensland 2012 p7).

5 Policy

An OHS Policy is a way the company “communicates its commitment to safe and healthy workplace and responsibilities of everyone in the workplace” (Workcover 2012).  Key elements to the policy includecommitment by the employer, provision of resources, defined OH&S responsibilities and a program  comprising of a  range of “ health and safety activities to enable the workplace to identify hazards, assess risks and implement control measures to ensure the highest level of workplace health and safety” (Workcover 2012). 

AS 4801 sets out an Australian standard for OHS and includes a clause for a policy ‘suitable to the nature and size of business’s operation’. AS 4801 (4.2-b) also “includes a commitment to establish measurable objectives and targets to ensure continued improvement”. This should be a core theme for any modern business wishing to implement a comprehensive OHS system.  

6 Conclusions

Conclusions can be drawn, that without a healthy workforce, business operations may not be sustainable.  Short-term sick days and extended sick days can have disruptions on business operations, not to mention the organization’s  legal obligation to “provide and maintain a safe work environment” (Guide to the Work Health and Safety Act 2011 p7). A comprehensive system of monitoring is advisable to prove management controls work.    

 by Neville Fuller