Abstract
States are moving toward tighter regulation of lead contamination, with California set to conduct hearings on draft legislation. The proper ventilation of industrial spaces is a complex topic and should be addressed through expert insights in order to sustain the health of the workforce and the greater community. This paper highlights and summarizes topics that plants should consider for reducing their lead exposure.
California moves to strengthen Lead regulation; other state and federal regulations may follow
The State of California has recently released proposed changes to its Code of Regulations regarding General Industrial Safety. The focus is on General Industry Safety Orders and specifically Sections 5155 and 5198. The changes found in the draft documents concern updates to exposure and action limits that were last drawn up based on data from the 80’s. In summary, blood levels of substances, including lead, are good indicators of potential health risks. As health technology advances and more is known, it makes sense to review the established criteria for action.
The toxic effects of lead on the human body are well known
Lead exposure has adverse impacts on human reproduction, neurological stress, heart disease, and high blood pressure. As the workforce ages, some of these conditions might already be prevalent so it makes sense to avoid or mitigate toxic materials that could contribute to increasing risks to health.
The more recent health studies by government and academia suggest that major negative impacts on human health can still be present at much lower blood levels than previously thought. Since 2016, the Centers of Disease Control(CDC) has proposed the limit for “elevated” blood levels to be 5 micro-grams per deciliter (5µg/dl). This is only one-eighth the current California standard. Lead contamination can occur through several pathways. Material can be picked up by touching and transferred to the mouth. It can also be transmitted through the air due to processes that produce airborne lead. One of the most direct is the smelting of lead for products and components. The breaking and recycling of lead products and the presence of lead oxides can introduce lead particles into the air. It is important to note that blood lead levels correlate with airborne lead levels. Lead dust can be deposited on surfaces and inhaled. California is addressing a perceived lenient standard for blood lead levels AND the permitted airborne lead levels for this reason. The proposed changes are relevant because they are more stringent than Federal norms AND the State of California has proven to be a bellwether of change regarding future changes at the Federal level.
The new recommendations set the Blood Lead Level to 10µg/dl
Public health experts propose that over a working lifetime, an individual should not exceed a 5-10µg/dl level. Scientific data predicts that blood level limits in the California proposal can be met if airborne lead Permissible Exposure Limits (PEL) be kept below 2.1µg/m3 of air. But in conference with industry and public health experts, such a level was not seen as feasible for industry to meet. Hence the establishment of a new limit of 10µg/m3 of air over an 8-hour time weighted average period. The new level is an 80% reduction from the old standard of 50µg/m3. The proposed provision to the standard has been on the legislative agenda since 2019. In addition, the official “action levels” that require active measures from an employer have been lowered from 30µg/m3 to 2µg/m3. One outcome is the establishment of a 12-month monitoring of an industry player should the presence of lead exceed this 2µg/dl level.
Along with a significant amount of new language for the industrial employer, the new proposal should produce Separate Engineering Control Air Limits (SECAL) for certain processes in industries. For example, Lead smelting operations would be at 50 µg/m3 and would decrease after a five-year introduction period. This may be applicable in industries other than lead product industries. Iron and Steel Foundries that produce low alloy metal castings are specifically mentioned in the draft California proposal.
How should an employer address these proposed regulations?
In general, mitigation strategies fall into three areas: avoidance, engineering controls, and protective measures. The industrial plant is a complex system, particularly regarding the ambient and process air management. Even if these changes to California regulation are not adopted or do not become nationwide, it’s worth reviewing a holistic approach to clean and safe air management in the industrial plant.
Understanding Air Contamination in the Plant
Air (and contaminated air) is not homogenous. Across the plant, there are many processes with differences in temperature, humidity, pressure, and velocity. A study of these factors will produce new information about zones in the plant that may generate higher airborne concentrations or allow leakage from place to place. Once a study of the space yields information about dust concentration, the owner should turn their attention to source capture of contaminants. In the case of airborne lead, the particles are heavy yet may be small (below 1 micron in the case of smelting), so the source capture needs to be designed, installed, and tested to achieve the maximum capture at the generation point.
Designing an Effective Filtration System
Once source capture has been properly understood, the analysis turns to a properly executed transport system. It is common for installed duct systems to underperform because of inadequate air movement, particularly when dealing with heavy and sticky lead dust. However, an economical and feasible resolution to this problem can be found through a flow and ventilation study that encompasses the duct transport system and the installed filtration subsystems. Understanding the filtration system also becomes crucial, as it is a complex air movement system in itself. To meet and exceed stringent regulations, proper consideration of factors like flow, temperature, moisture, and filter media selection is essential, especially in the case of lead pollution. Even if lead is not the primary concern, conducting a thorough evaluation of existing or new filter specifications will lead to an optimum result.
Challenges and Solutions for HEPA Filtration
In melting and furnace applications, discussions about high-efficiency particulate air (HEPA) filtration are common, especially since small combustion particles are produced. However, HEPA solutions tend to be more effective when integrated as part of a sequential set of filter elements. The challenge with HEPA filter elements lies in their difficulty to clean, placing a burden on the owner in terms of disposal and the purchase of new filter elements. An additional operational issue faced by plants is the need to stay in production while filter media is being serviced. To address this, designing a system for filtration redundancy may be necessary. Despite these challenges, there are already systems available that successfully meet strict lead pollution targets, achieving levels as low as 0.5µg/m3 at the exit of a baghouse, which is well below the action level.
Integrating Personal Protective Equipment (PPE) and Contamination Control
Personal protection in the proximity of toxic materials is a broad topic not addressed in detail here. However, several simple and more complex technologies exist to protect the worker from surface or airborne contaminants. The business operator can obtain the best value when selecting personal protective equipment (PPE) if the other engineering steps discussed here have been covered. By designing, controlling, and segregating potential areas of contamination, it should be possible to reduce lead levels in certain zones and reduce the investment in PPE while still adhering to minimum regulatory requirements.
Conclusions
State and national regulations are likely to become more stringent over time due to new epidemiological data showing evidence of the negative effects of lead toxicity. Much has been achieved to reduce employee exposure, but more can be achieved by rigorous study of each specific manufacturing environment. The public is watching. Many lead-based products are no longer in widespread use, yet the public expectation is that allowable limits will continue to reduce. It is not necessarily a profit-eroding scenario for industrial owners to address lead mitigation. Well-designed studies and engineering controls, from source capture to filtration, can help the user meet the requirements at a reasonable cost.
