Toxic metals include heavy metals (such as lead, mercury, and nickel) and other metals (aluminum, iron, tin) that may pose a significant threat to human health under certain circumstances. While toxic metals are naturally found in the environment and are present in our bodies, in the water we drink, and the food we eat, they create a substantial risk when exposure occurs at higher levels. 

Occupational tasks involving heavy metals, such as metal work and machining activities (for example, fabrication, smelting, forging, welding, grinding, refinishing, foundry work, and repair work) tend to have higher exposure levels. At greater levels, toxic metals become dangerous contaminants and pollutants, negatively affecting workers’ health. Toxic metals create a concern because of: 
  • bioaccumulation (the metals become more concentrated in the body over time; the body struggles to get rid of accumulated metals) 
  • multiple routes of exposure (ingestion, inhalation, and skin contact) 
  • the ability to quickly poison a worker directly exposed (that is, toxic metal poisoning) 
  • known or suspected human carcinogenicity (varies per metal)
  • the high possibility of cross-contamination (transfer from the work area of concern to other areas in the workplace, and even a worker’s vehicle and home)
OSHA has established regulations for specific toxic metals under 29 Code of Federal Regulations 1910, Subpart Z, Toxic and Hazardous Substances. But for many organizations, controlling worker exposures and preventing cross-contamination in surrounding and adjacent work areas are difficult challenges. This article advises how to look for toxic metals in the workplace, emphasizes compliance strategies, and identifies best practices to control toxic metal exposures and minimize cross-contamination. Defer to the hierarchy of controls when selecting controls and apply the plan-do-check-act cycle of continuous improvement to evaluate the effectiveness of controls and implement new strategies for reducing cross-contamination. HOW TO LOOK FOR TOXIC METALS Conducting exposure assessments and risk assessments is essential to identify and document the health and safety hazards associated with toxic metal use and generation. These assessments must include professionals who are familiar with the hazard identification process. Typically, a safety officer conducts a baseline safety assessment to analyze work processes for safety hazards, while an industrial hygienist evaluates the work environment and takes samples to assess health hazards. An environmental officer evaluates environmental hazards and impacts, and sometimes the fire department assesses fire hazards. This is a collaborative effort: often, the assessments involve gathering information from supervisors and other workers with knowledge of the process to determine what is typical on a day-to-day basis. Ideally, baseline assessments are best conducted prior to the introduction of a new material, process, or procedure in the workplace, but this is not always possible. If a baseline assessment has not been completed in work areas using or generating toxic metals, it is important to conduct an assessment as soon as possible to assess existing and potential risks. Baseline assessments help organizations look at the unique processes and tasks associated with toxic metals to obtain a benchmark of potential hazards and exposures in the workplace and assess how they can affect the entire organization. This information is useful in determining whether a current risk or exposure exists, the level of that risk or exposure, and whether the organization needs to take action. 
Workers can track toxic metals through adjacent areas or across the facility to the changing room, break rooms, or their office.
On a qualitative level, conduct interviews and make field observations to gather information on processes and work areas where toxic metals are used or generated. Observe each process involving toxic metals, the rooms and buildings in which the processes operate, the surrounding areas (such as bathrooms, break rooms, and adjacent operations), and the movement of workers into and out of these work spaces. Identify where workers are directly generating or using toxic metals, the routes of possible exposure, and likely areas to experience cross-contamination. (Workers can track toxic metals through adjacent areas or across the facility to the changing room, break rooms, or their office.) Make a list of areas and processes where workers handle or work with toxic metals, the products and materials used, areas that may have cross-contamination, and any hazards identified.  Quantitatively, sample each unique task as each has differing levels of exposure. The baseline assessment may include air sampling, wipe sampling, or other sampling methods and analysis. Assess risk by comparing worker exposure levels against exposure limits. Airborne toxic metal exposure limits like OSHA permissible exposure limits and short-term exposure limits vary for each toxic metal. Also, refer to other authoritative limits such as NIOSH recommended exposure limits and ACGIH threshold limit values, when applicable. For surface contamination, review maximum allowable surface contamination limits listed in federal and state environmental regulations and authoritative standards (such as the TLVs). OSHA says the goal for surface contamination is “as free as practicable,” which means that organizations need to keep surface contamination to a minimum so surfaces don’t become sources of employee exposure. Document all identified health hazards as well as the results of air and wipe sampling.  Use the baseline assessment to characterize workplace hazards and exposures, establish action plans, employ hazard controls, and implement best practices to mitigate hazards, control exposures that reach levels at or above exposure limits, and address areas where surface contamination exists.  BEST PRACTICES AND STRATEGIES Elimination and Substitution Elimination and substitution, the most effective ways to protect workers against toxic metals, involve removing or replacing the material, equipment, or process that presents a hazard. These methods are the most difficult to implement (especially for existing processes) but implementation is easier if considered before a new process is introduced (that is, during the planning and design phases).  Identify all processes involving products and materials containing toxic metals. Determine the necessity of each process. Decide whether it is possible to remove any process (or part of a process) without a significant impact on the end product, thereby eliminating the hazard.  Also look at the products and materials containing toxic metals and investigate available substitutions. If a substitution is available, evaluate the new product thoroughly before use to see if it is practical for the process, and if its use would result in any changes to the end product or introduce new (or higher risk) hazards. While substitution seems practical, many organizations are unable to use alternate products. For example, substituting a chromate-free primer to paint aircraft for a primer that contains hexavalent chromium is not always feasible. While safer to use, the chromate-free primer will peel off the aircraft sooner, requiring earlier rework, repair, or refinishing.  If elimination and substitution are unlikely options, consider outsourcing the work or the hazardous processes, which allows another organization to address the risks and assume liability while maintaining the quality and integrity of the end product. Ventilation Ventilation is one of the most effective control options available for toxic metals. Identify a qualified person to examine existing ventilation systems and confirm they are adequate for the filtration of toxic metals. Many organizations have designated or enclosed work areas (for example, blast booths and spray painting booths), but several actions can result in better control of toxic metals.  Assess the circulation patterns of the heating, ventilation, and air conditioning system where toxic metals are used or generated. This assessment is especially important if the work area was not originally designed and designated for the use or generation of toxic metals. Determine whether the air flows back into the work area, into a different area, or even outside the building. Consider installing a high- efficiency particulate air (HEPA) filter in the HVAC system when the air flows into work areas where toxic metals are used or generated; recycling air possibly spreads contamination and may expose workers to toxic metals. Know that pushing contaminated air through outdoor venting may also require special permits.  Ensure there is negative pressure in the area where toxic metals are used or generated (Figure 1) to contain dusts, fumes, vapors, and other contaminated air. Adjust the HVAC system to create negative pressure, if possible. Consider the need for additional or modified ventilation systems where the current HVAC system is incorrectly driving pressure differentials. 
Figure 1. Negative pressure. vs. positive pressure room. A negative pressure room is ideal for a regulated area. Negative room pressures are present when air flows into the regulated area, containing dusts, fumes, and vapors within the area. Positive room pressures are present when air flows from the regulated area to the outside. Positive room pressures promote cross-contamination in adjacent work areas. Sometimes you can identify room pressure by simply opening the door with the ventilation system running to see if air rushes into or out of the room, or if there is resistance when opening the door. 
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Look at options to control dust. Choose equipment and tools equipped with HEPA filtration options to capture a large amount of dust at the source or point of operation. When additional ventilation is needed, consider the use of mobile ventilation units, where a unit plugs into an outlet and a movable exhaust arm stretches to the point of operation, drawing airborne toxic metals away from workers’ breathing zones. In some organizations, it may be possible to install these moveable exhaust arms as permanent parts of the ventilation system.  In any case, include all ventilation systems in a maintenance program. Maintaining ventilation ensures continued safe operation and validates the system is running as effectively and efficiently as possible. Check manufacturer guidelines for testing, maintenance, and verification expectations.  Exposure Monitoring Plan An exposure monitoring plan is necessary to monitor the risks associated with toxic metals, confirm controls are reducing the risk, and prevent occupational injuries and illnesses. Refer to the baseline assessment as a starting point to pull the plan together. An exposure monitoring plan must be specific to the toxic metals present in the organization and must establish the sampling strategies and protocol to follow for specific exposures. Establish a plan for each task that generates or uses toxic metals. At a minimum, plans should include the objectives of the sampling, what to sample, whom and where to sample, how to sample, when to sample, how long to sample, how many samples to collect, and how to handle, store, and ship samples. Exposure monitoring may pair qualitative assessments with sampling to evaluate controls or further observe tasks and processes.  Where maximum allowable surface contamination limits are not applicable to the toxic metals under consideration, consider defining what “as free as practicable” means to the organization in exposure monitoring plans (in other words, identify the minimum detection level required by  the sampling method and analytical protocol). Collect wipe samples before work, after work, and after housekeeping for areas where work is performed with toxic metals and other areas suspected of contamination (such as break rooms). Use these results to establish a baseline value, or the “as free as practicable” level for each work area—these are the results workers must strive to achieve each time they complete housekeeping practices. Exposure monitoring plans can identify these baseline values and set a frequency for periodic wipe sampling to evaluate surface contamination levels and assess the effectiveness of housekeeping.  Exposure limits vary for each toxic metal. It is a best practice to use the most stringent exposure levels available when establishing exposure monitoring plans. Regulated and Transition Areas Many toxic metals require organizations to establish a regulated area when exceeding OSHA PELs and STELs. OSHA defines a regulated area as a demarcated zone where airborne concentrations of a substance exceed, or can reasonably be expected to exceed, established exposure limits. The intent of a regulated area is to define and segregate the hazardous work area, minimize the number of persons within the area, and protect persons outside the area from airborne exposure to the toxic metals. Regulated areas can be permanent or temporary (useful for maintenance and non-routine tasks). While OSHA does not require regulated areas for all toxic metals, it is good practice to establish a regulated area for any work process where toxic metal exposures meet or exceed the most stringent exposure levels available.  It is just as important to define transition areas to further control cross-contamination. Transition areas are not regulated areas since they do not exceed airborne exposure limits; however, they are prone to cross-contamination from the regulated work area. Transition areas are typically adjacent to regulated areas, serving as a throughway for workers to move between the general workspaces and the regulated area. Examples of transition areas include changing rooms, shower areas, halls, and walkways.  Use the baseline exposure and risk assessment results to define the perimeters of regulated areas, determine the need to isolate transition areas (for example, a designated break room only for those who work in a regulated area), and establish new transition areas as necessary (such as a new restroom specifically for a regulated area). Figure 2 shows a path of travel from a general workspace, through transition areas, and into a regulated area to minimize cross-contamination. 
Figure 2. Transition from a non-regulated work area into a regulated work area. To achieve ultimate flow and reduce cross- contamination, designate a clean changing room where workers remove their street clothes. Have workers transition through the shower room and into the contaminated changing room, where the storage lockers contain protective clothing, PPE, and other gear for use only within the regulated area. When leaving the regulated area (and not anticipating a return to the area for the day), ask workers to change in the contaminated changing room, shower, then dress back into their street clothes in the clean changing room before proceeding to other non-regulated work areas. 
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Demarcate all regulated and transition areas and post signage on all approaches to these areas. Make sure posted signage is visible and consistently posted throughout each area, complies with any regulatory requirements for specific toxic and hazardous substances, and is available in the primary language of the workers. Access Restrictions  Identify all workers assigned to each regulated area. Consider other personnel who may need access. Account for maintenance tasks, filter changes, dust collection, waste and laundry pickup, and housekeeping tasks that need to be performed. Generate a list of authorized personnel who may access the regulated area and share it with supervisors. Ask supervisors to monitor doors and access points to prevent unauthorized entry. Also consider the use of locks, code pads, or badge scanners to limit access. When implementing these measures, make sure workers can still evacuate the area during an emergency.  Settling Time Calculating the settling time, or the time it takes for airborne particulates to fall to the floor, may be useful in further controlling cross-contamination to transition areas and general workspaces. The settling time depends on the size, shape, and weight of airborne particulates. While workers are waiting for the “dust to settle,” they can vacuum themselves off or perform other tasks that do not generate airborne dust. When the settling time passes, workers can leave the regulated area while minimizing the amount of airborne dust leaving with them. Housekeeping Put together a detailed housekeeping plan by listing any item that requires periodic cleaning, including equipment (such as a high-efficiency particulate air vacuum), materials (waste containers, laundry, sticky mats), and work environment (horizontal surfaces, high contact surfaces, ceiling rafters). Collaborate with workers who perform tasks in regulated areas to make the plan as comprehensive as possible.  Assign responsibility for carrying out each item in the plan. Identify the cleaning frequency for each item and create a schedule to perform housekeeping tasks in the required timeframe. Keep cleaning logs to show execution of the plan and schedule. Consider forming a team to spot-check housekeeping practices or include them in periodic self-inspections. Review and update the plan on an annual basis and as changes occur.  Street Clothing and Laundering OSHA defines “street clothing” as the clothing workers wear to and from the workplace. Prohibit the use of street clothes under work garments and protective clothing to prevent cross-contamination. Do not allow workers to take soiled clothing home from the workplace because they can carry contamination home with them. Utilize a third party to launder contaminated protective clothing, or launder it in-house. Coordinate laundry processes with subject matter experts for proper signage and labeling requirements, communicating hazards and unique precautions to launderers, and transportation requirements.  Training and Supervision Training is essential to communicate the toxic metals present in the workplace and precautions to take. Train workers to safely work within regulated areas. Education must include the toxic metals present, signs and symptoms of exposure, emergency procedures, hazard controls, and personal protective equipment requirements. Rules in regulated areas may include no eating or drinking; no touching materials, equipment, or surfaces; leaving personal items behind before entry; and washing hands and face after leaving. Provide refresher training and briefings as necessary so workers understand the expectations. Arrange additional training for workers expected to carry out health and safety tasks in these areas (for example, conduct safety inspections and validate housekeeping practices). Ensure supervisors have a thorough understanding of established rules and requirements for regulated areas so they serve as safety leaders in the organization. Confirm supervisors understand the importance of enforcing all rules and procedures.  Educate visitors and contractors as well on relevant topics to stay safe at your organization. This is especially important if they plan to work in regulated areas. Ensure visitors and contractors have required PPE prior to entry. For example, provide disposable shoe covers to anyone walking through a regulated area to keep contamination off their shoes.  Inspections Safety inspections help identify hazards in regulated work areas. Consider developing unique inspection checklists for each regulated area based on control measures and housekeeping practices. Include items such as seals on doors and collection systems to prevent leaks, dust accumulation on horizontal surfaces and elevated surfaces, and emptying of waste collection points. Document inspection findings, even those that workers fix on the spot. Keep in mind that only authorized personnel may be able to complete these inspections. Don’t forget to include contractor work activities in safety inspections to validate all contractors are following safe work practices and PPE requirements.  Hazard Abatement Many organizations have a process in place to capture and monitor hazards. This process can be extended to regulated areas. Utilize the hazard abatement process to address inspection findings, reported hazards, worker concerns, and trends associated with regulated areas. Assign responsible persons, establish timelines for completion, identify corrective actions and interim controls, and track each item to closure. Keep workers informed on the status of open action items and ask for their feedback on possible mitigation measures.  THE BEST STRATEGY Any organization with processes involving toxic metals should think about which strategies would work best for each regulated area. Implementing every strategy may not be feasible, but upon completion of a baseline assessment, organizations will be better suited to choose strategies that meet their capabilities.    LORI SCHROTH, DBA, MS, CSP, CIT, is a senior safety and environmental professional at Concurrent Technologies Corporation in Johnstown, Pennsylvania. She can be reached at. BRANDON J. HODY, MS, CSP, is a safety and occupational health professional at Concurrent Technologies Corporation in Johnstown, Pennsylvania. He can be reached at. Send feedback to The Synergist.

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Strategies for the Workplace
BY LORI SCHROTH AND BRANDON J. HODY
Conquering Toxic Metals
Although the print version of The Synergist indicated The IAQ Investigator's Guide, 3rd edition, was already published, it isn't quite ready yet. We will be sure to let readers know when the Guide is available for purchase in the AIHA Marketplace.
 
My apologies for the error.
 
- Ed Rutkowski, Synergist editor
Disadvantages of being unacclimatized:
  • Readily show signs of heat stress when exposed to hot environments.
  • Difficulty replacing all of the water lost in sweat.
  • Failure to replace the water lost will slow or prevent acclimatization.
Benefits of acclimatization:
  • Increased sweating efficiency (earlier onset of sweating, greater sweat production, and reduced electrolyte loss in sweat).
  • Stabilization of the circulation.
  • Work is performed with lower core temperature and heart rate.
  • Increased skin blood flow at a given core temperature.
Acclimatization plan:
  • Gradually increase exposure time in hot environmental conditions over a period of 7 to 14 days.
  • For new workers, the schedule should be no more than 20% of the usual duration of work in the hot environment on day 1 and a no more than 20% increase on each additional day.
  • For workers who have had previous experience with the job, the acclimatization regimen should be no more than 50% of the usual duration of work in the hot environment on day 1, 60% on day 2, 80% on day 3, and 100% on day 4.
  • The time required for non–physically fit individuals to develop acclimatization is about 50% greater than for the physically fit.
Level of acclimatization:
  • Relative to the initial level of physical fitness and the total heat stress experienced by the individual.
Maintaining acclimatization:
  • Can be maintained for a few days of non-heat exposure.
  • Absence from work in the heat for a week or more results in a significant loss in the beneficial adaptations leading to an increase likelihood of acute dehydration, illness, or fatigue.
  • Can be regained in 2 to 3 days upon return to a hot job.
  • Appears to be better maintained by those who are physically fit.
  • Seasonal shifts in temperatures may result in difficulties.
  • Working in hot, humid environments provides adaptive benefits that also apply in hot, desert environments, and vice versa.
  • Air conditioning will not affect acclimatization.
Acclimatization in Workers

Why Is the Prevalence of Asthma Increasing?
It is not clear why the prevalence of asthma has increased, but a 2019 journal article focused on the epidemiology of asthma in children and adults describes several hypotheses that have been considered over the years:
  1. increased exposure to indoor allergens due to tighter insulation in modern housing as well as the increased use of plush furniture and carpets has contributed to an increase in asthma and other allergies
  2. reduced exposure to “unhygienic environments” early in life may lead to the increased prevalence of asthma and similar conditions
  3. the “microbial diversity” hypothesis, which suggests that “microbial diversity in the gut mucosa and respiratory tract are the key factors in priming and regulating the immune system” (therefore a lack of exposure to nonpathogenic microbes might explain the increased prevalence of asthma and other allergic diseases)