Pictured: Flexible intermediate bulk containers in a warehouse.
Powder handling in the agrochemical industry presents complex exposure scenarios, as it is rarely the goal of an operation to simply “move powder from container A to container B.” The inherent toxicity of powders, their bulk quantities, particle sizes (which range from a few microns to pellets), and packaging constraints combine to test both the technical know-how and the creativity of the industrial hygienist.
Powders used in the agrochemical industry range from basic, well-known chemicals to potent carcinogens, neurotoxic compounds, endocrine disruptors, skin sensitizers, and pyrethroids that can cause transient paresthesia. Toxicological data packages for many of these chemicals are still incomplete. Because these products are designed to be active in biological systems, they tend to be active in the human body.
Powders are either received or packaged into small sacks, drums, or flexible intermediate bulk containers, or they are directly offloaded into silos. FIBCs, commonly known as “big-bags,” can hold anywhere from 500 to 1,000 kilograms of intermediate or final products. Unfortunately, the packaging and handling of these products are not the agrochemical industry’s main concerns; IHs are often on their own in figuring out best practices.
Powder handling is hardly a new challenge, but we hope our experiences in applying traditional IH control approaches—such as containment and organizational control within a dynamic manufacturing environment—will be useful to others in similar workplaces. For the purposes of this article, imagine a chemical manufacturing site with more than 20 production buildings, many workstations, and a range of products with varying toxicity.
A TEAM APPROACH
It may sound counterintuitive to the IH, but in powder handling the key to effective exposure control is not in conducting exposure assessment. While exposure assessment is absolutely part of our strategy, we’ve found the answer to be a comprehensive, integrated approach using a team of experts in the following roles: health, safety, and environmental (HSE) professional; chemist; process engineer or process owner; maintenance engineer; project manager or owner; asset manager; and operator or asset user. We have found that individuals in each of these roles, as described below, should be involved in all projects at some point.
- HSE professional.Provides critical information regarding process safety, operational safety, and industrial hygiene, and gives feedback on where potential exposures may occur in the handling process.
- Chemist. Provides feedback concerning the materials’ physical aspects and any byproducts. (Although materials are often selected before a project reaches a site, the chemist would ideally be able to influence which materials are used based on their toxicity.)
- Process engineer.Provides guidance on which type of technologies and assets are needed and gathers information about similar processes that may already exist on site.
- Maintenance engineer.Helps to assess how maintenance will be performed and can influence it if necessary.
- Project manager or owner.Provides feedback on available installations or the possibility of designing a new system, works with equipment suppliers to find the right installations, and ultimately has the final word on which type of asset will be used or purchased.
- Asset manager.Acts as the final “owner” of any equipment that is put in place and provides feedback if the project includes the modification of an existing process or equipment.
- Operator or asset user.Provides feedback as a future user with a critical eye for details that others may not recognize when designing equipment.
EQUIPMENT DESIGN
Project teams should work with suppliers to ensure that equipment provides the proper containment and, if possible, that it is the most “comfortable” in terms of ergonomics. Remember, not every installation has to come “off the shelf ”; in some industries, including the agrochemical industry, assets are often assigned to multiple products. Designing equipment to meet the specifications for multiple products ensures proper containment for products of different toxicities. During the design phase, we aim to achieve 10 percent of the exposure limit via design of the installation. This goal helps us account for the well-known variation inherent to IH exposure distributions and ultimately reduces the need to rely on personal protective equipment. This approach also helps to achieve compliance with varying exposure limits for the multiple products in use.
Because of our location, we must look to the European Union’s regulation on the Registration, Evaluation, Authorization and Restriction of Chemicals, which requires companies to work under strictly controlled conditions when the toxicological profile of a product is unknown or incomplete. Although REACH does not recommend specific exposure limits for these products, many companies implement a relatively low internal exposure limit to ensure they are operating under strictly controlled conditions. While this prudent REACH guideline allows us to protect workers as unknown products are increasingly introduced into production, compliance can be a major investment. For example, we once had a situation in which an installation was originally used for a product with an exposure limit 50 times greater than that of the product that followed (imagine total dust versus strictly controlled conditions). To allow for the safe handling of both products, a supplier designed a piece of equipment for us that could easily be transformed into a glove box. We chose an open-faced laminar flow secondary containment around a discharging cone (see Figure 1) that can be transformed into a fully contained glove box, if necessary. As previously mentioned, ergonomics is another important consideration when working with equipment suppliers. In our case, the supplier designed our new equipment so that the glove box height and handle placement could be easily adjusted. For a system that is held in place by a fixed frame, you might consider designing the equipment so that each operator can pneumatically regulate the glove box height via a simple button. In a simple clamp system where no glove box is present, adjusting handle height so that the operator can work at proper shoulder height can also reduce exposure, as the operator will no longer be required to approach the cone to close the clamp.
PREDICTING EXPOSURES
The collective knowledge of project team members is essential to predicting exposures. Any time a new product is introduced on a site, we recommend creating a project team to delve into all possibilities. This team will evaluate all potential assets to assess if any are suitable for the production in question or if it is necessary to buy a new installation. When assessing previously employed assets, the team should review existing air sampling results and product specifications to compare previous experiences with similar products or with the assets. This step helps ensure that a site is as prepared as possible when a new campaign starts. But it’s not possible to foresee everything that will happen once production begins. For example, we once had unexpected blockages and break-ins, and we had to replace parts on the installation for a new product we’d never produced before. We’d assessed all possible scenarios using each possible installation, considered previous sampling data, and used exposure prediction tools such as the Advanced REACH Tool
to predict exposures—and still had to adapt once production had begun.
Chemists can be especially helpful in predicting exposures. We once dealt with a product for which we would have prescribed a very basic installation, based on its toxicological profile and exposure limit; however, the chemist provided us with feedback from preliminary lab experiments that showed that the powder was extremely fine and easily dispersed with basic controls. This knowledge led us to opt for a higher level of containment.
This leads us to another piece of advice: ask for physicochemical property tests in advance. Data such as particle size, water content, ease of compaction during storage, and sublimation potential can help predict potential exposures. We once had a case where some of the air sampling results for a new powder were coming back as below the limit of detection for the powder form, but we had fairly high results when we sampled for vapors. Now we ask our research and development team to perform sublimation tests on new powders that aren’t familiar to us.
REDUCING EXPOSURES
IHs can do a variety of things to help project teams reduce occupational exposures to powders, such as ask for bigger particles. When possible, teams should work with suppliers and chemists to use pellet-like granules of a product rather than the powder form. Using larger particles can help reduce both exposures during manual handling and amount of residual product left in the packaging during disposal. If a fine powder is required, an IH should request that a humid product be used (rather than a dry one). Keep in mind that humid products often have problems with compaction, especially during storage. A chemist may be able to coordinate compaction testing or predict a product’s level of compaction based on a similar product.
Automating product offloading as much as possible is the best approach in terms of limiting exposure—but perhaps not in terms of limiting expense. Offloading from a tanker car directly into a silo is ideal, but for a small-scale or one-shot production, discharging big-bags may be the only option. In this case, IHs can work with chemists and others in the supply chain to influence the type of packaging based on the installations available and the quantity of product that will be produced. For example, if both a big-bag discharging station and a drum discharging station are available, and we expect to use 1 ton of product per batch, there is a clear argument to find a supplier that will provide big-bags instead of drums. Two big-bag discharges are better in terms of exposure and ergonomics, compared with 10 to 14 smaller drum discharges. ADVERTISEMENT
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In powder handling, administrative controls remain very important even when technical controls are in place. Technical controls are often well thought out for the loading and offloading phases but not necessarily for the tasks that precede or follow them. Such tasks include taking a sample from an FIBC, connecting or disconnecting an FIBC, and discarding empty packaging with product potentially remaining inside. A good place to start when assessing exposures to powders is to review work practices and make sure that workers are trained using the same methods. Workers often develop their own “best practices,” which can be beneficial because they know the installation best; however, it’s sometimes difficult to share this information across multiple shifts.
When investments are not possible, these worker- developed best practices can be a valid method for reducing exposures. For example, some new FIBC discharge stations come with a feature to extract the air and residual powder from the FIBC at the end of the charge so that it has the least amount of residual dust during disconnection and disposal. On older installations or on installations driven by gravity, this option does not exist. A best practice we’ve learned, developed by a worker, is to lower the hoist with the empty FIBC and to tie it closed while collapsed before removing it from the installation. It seems simple, but we have seen that most exposures come from creating a dust cloud while disposing of these FIBCs when air and powder remain inside.
On rare occasions, we’ve been able to reduce the inherent hazard of a product by modifying or reducing specific hazardous components. This is often outside the area of influence of even very senior organizational industrial hygienists, as these types of changes may affect product efficacy or market registration, and may result in changes to a product’s safety data sheet or transport labeling. Even so, we recommend exploring these possibilities when a product’s risk level warrants it. For example, we were once able to reduce the content of a certain solvent, which changed the hazard classification of the product and ultimately led to a less hazardous work operation.
EXPOSURE ASSESSMENT CHALLENGES
Even after employing all appropriate controls, one difficult challenge remains: assessing exposures for workers. The traditional approach of selecting similar exposure groups is impractical when operators are engaged in varying tasks and there is no discernable pattern in their activities. Even where the same product is used in multiple areas on site, it’s rarely with the same type of installation, packaging, or quantity. Timing of production and shift changes, as well as the tonnage of the campaign, are additional factors that can affect exposures. In one shift, a worker might complete one discharge on three different installations; the next day, he or she might complete three discharges on a single installation, which means three times the exposure for that specific workstation compared to the day before.
So, how do we adequately assess these exposures? We prefer to follow a task-based approach. This may require a greater number of samples than the SEG approach; however, we prefer more sampling to the incredible variability that would result if we attempted to pool exposure data and extrapolate to the work force. To stay within our monitoring budgets, we prioritize the tasks using inputs such as the hazard, risk of exposure, effectiveness of control measures, volume of use and number of people potentially exposed. Our ideal is to fully characterize the exposure profile per workstation or task, including statistical considerations of OEL compliance.
AN IH’S ROLE
Industrial hygiene was historically considered one part science and one part art. The development of detailed hazard information, advances in tools for modeling and predicting exposures, and the use of statistics in analyzing OEL compliance have increasingly moved IH more toward science-based approaches. There is still a great deal of art involved in being a successful IH; we must be adept at influencing the way activities are performed from beginning to end. Effective IH practice is more than acquiring core knowledge of subject areas. We must engage various specialists in their areas of expertise and continuously show the value we bring to protecting the health of employees.
SAMANTHA CONNELL, MSPH, is an industrial hygienist in Valais, Switzerland. She can be reached via
email
.
BRIAN SCHMIDT, MSc OH, CMFOH, is global occupational hygiene manager, Biopharma, at Merck Group, Switzerland. He can be reached via
email
.Acknowledgement:
The authors would like to recognize Christian Fracheboud, project engineer. Many of the solutions discussed in this article resulted from his hard work. He has become a champion for hygiene in the realm of engineering.
Figure 1.
FIBC emptying station (photo courtesy of JetSolutions).Tap on the graphic to open a larger version in your browser.
Technical controls are often well thought out for the loading and offloading phases but not necessarily for the tasks that precede or follow them.
Reducing the Hazards of Bulk Powders in the Agrochemical Industry
Powder Handling in Production
