On this page
Key Summary: When a chemical substance has no formal occupational exposure limit (OEL), kick-off values give you a defensible, conservative benchmark you can apply today. DOHSBase derives each kick-off value from the 10th percentile of the limit-value distribution for substances sharing the same GHS/CLP hazard classification — meaning 90% of the substances in that hazard category have higher (less strict) formal limits than the kick-off value you’ll use. The methodology was introduced by DOHSBase in 2005, updated in 2014 to align with GHS/CLP, and peer-reviewed in 2016 in the Annals of Work Exposures and Health. The Dutch Labour Inspectorate (Inspectie SZW) has accepted kick-off values since 2012, so using them in a Dutch risk assessment is a defensible choice under inspection. DOHSBase Online contains over 100,000 kick-off values — covering the vast majority of substances you’ll encounter in practice.
In occupational hygiene, safeguarding workers from hazardous substances is paramount. However, many substances lack formal occupational exposure limits (OELs), posing challenges for effective risk management. To address this gap, DOHSBase introduced the concept of “kick-off” values in 2005, with an update in 2014. These values serve as conservative starting points for managing substances without established OELs, ensuring a higher standard of workplace safety.
What Are Kick-Off Values?
Kick-off values are conservative occupational exposure benchmarks developed by DOHSBase for chemical substances that lack a formal occupational exposure limit (OEL). They are defined as the 10th percentile of the limit value distribution for substances with similar hazard classifications under GHS/CLP. This means that 90% of substances in the same hazard category have higher limit values than the kick-off value.
The Problem: Thousands of Substances Without Exposure Limits
Of the hundreds of thousands of chemical substances in commercial use, only a relatively small fraction have formally established occupational exposure limits. Deriving a health-based OEL is a resource-intensive process that requires comprehensive toxicological data, expert review, and often years of deliberation by scientific committees. As a result, the vast majority of substances that workers encounter in practice have no official guidance on what constitutes a safe airborne concentration.
This creates a practical dilemma for occupational hygienists and employers. Regulations such as the Dutch Working Conditions Act require employers to assess and manage the risks of all hazardous substances used in the workplace – not just those with published OELs. Without a quantitative benchmark, professionals are left to make subjective judgments or default to overly conservative (and often impractical) assumptions.
Kick-off values were developed specifically to fill this gap. They provide a scientifically grounded, conservative estimate of a safe exposure level for substances that lack formal OELs, enabling structured risk assessment where none was previously possible.
Understanding Kick-Off Values
Kick-off values are derived from the distribution of existing limit values for substances sharing similar hazard classifications, specifically H-statements under the GHS/CLP (Globally Harmonized System / Classification, Labelling, and Packaging) regulations. Defined as the 10th percentile of this distribution, a kick-off value indicates that 90% of substances within the same hazard category have higher limit values. This conservative approach ensures that even in the absence of formal OELs, there is a benchmark to guide safe exposure levels.
How Kick-Off Values Are Calculated
The calculation proceeds as follows:
-
Identify the substance’s hazard classification. Using the GHS/CLP system, each substance is classified according to its H-statements – standardized codes that describe specific health hazards (such as H301 for acute oral toxicity or H350 for carcinogenicity).
-
Group substances by hazard category. All substances in the DOHSBase database that share the same most severe H-statement are grouped together. These groupings follow the principles of Control Banding, which assumes that substances with similar hazard profiles warrant similar levels of control.
-
Analyze the limit value distribution. Within each hazard group, the existing OELs of all substances that do have formal limits are collected and their statistical distribution is examined.
-
Determine the 10th percentile. The kick-off value is set at the 10th percentile (tolerance lower bound) of this distribution. This means that 90% of substances in the same hazard category have OELs that are higher (less strict) than the kick-off value. The choice of the 10th percentile ensures a conservative benchmark: applying a kick-off value will, in the vast majority of cases, result in a level of protection equal to or greater than what would be achieved with a formal OEL.
The result is a single concentration value (expressed in mg/m3 or ppm, as appropriate) that can be used in place of a formal OEL for risk assessment, exposure monitoring, and compliance purposes.
Connection to GHS/CLP H-Statements
The kick-off value methodology is fundamentally linked to the GHS/CLP classification system. H-statements are the internationally harmonized language for describing chemical hazards, and they form the basis for grouping substances into hazard categories. Because H-statements are assigned based on intrinsic substance properties – toxicity data, epidemiological evidence, and physicochemical behavior – they provide a scientifically meaningful basis for comparing substances and deriving statistical benchmarks.
When the GHS/CLP system replaced the older EU system of R-phrases, DOHSBase recalculated all kick-off values in 2014 to align with the new classification framework. The 2014 update also incorporated an expanded database and improved Control Banding schemes, resulting in more robust and representative kick-off values.
Significance of Kick-Off Values
| Aspect | Details |
|---|---|
| Definition | Kick-off values are defined as the 10% lower limit of the limit value distribution of substances in a hazard category |
| Purpose | Provides a conservative benchmark for substances lacking formal occupational exposure limits (OELs) |
| Application | Used in risk assessments, regulatory compliance, and occupational hygiene strategies |
| Regulatory Recognition | Accepted by the Dutch Labour Inspectorate since 2012 for self-inspection compliance |
| Scientific Basis | Derived from limit value distributions based on H-statements and Control Banding schemes |
| Use in DOHSBase Online | Enables quick access to kick-off values for over 100,000 substances to enhance workplace safety |
Regulatory Recognition
The practicality and scientific rigor of kick-off values have earned them formal recognition from regulatory authorities. Since 2012, the Dutch Labour Inspectorate (Inspectie SZW) has referenced DOHSBase’s kick-off value methodology in its guidelines for determining limit values. This means that when an inspector evaluates whether an employer has adequately assessed and managed chemical risks, the use of DOHSBase kick-off values is accepted as a valid approach for substances without formal OELs.
This recognition is significant because it provides legal certainty for employers. Rather than facing the uncertainty of having no benchmark at all, organizations can apply kick-off values with the confidence that their approach meets regulatory expectations.
Practical Application in Workplace Safety
In day-to-day practice, kick-off values are used in the same way as formal OELs:
- Exposure assessment: Compare measured or modeled airborne concentrations against the kick-off value to determine whether exposure is acceptable
- Control measure design: Use the kick-off value as the target concentration when designing ventilation systems, containment measures, or other engineering controls
- Risk prioritization: When multiple substances lack formal OELs, kick-off values allow you to rank them and focus resources on the highest risks
- Compliance documentation: Include kick-off values in your hazardous substance register and risk assessment reports as the applicable exposure benchmark
If a kick-off value proves technically or economically infeasible to achieve, this signals that a more detailed toxicological assessment may be warranted to establish a substance-specific, health-based OEL. In this sense, kick-off values serve as both a practical tool and a decision point in the risk management process. Learn more about how kick-off values fit within the limit value hierarchy.
Would you prefer a background article with in-depth knowledge right away?
For a deeper understanding of the development and application of kick-off values, including the full statistical methodology and comparison with other approaches, you can read the background article provided by DOHSBase.
Development and Implementation
- Limit Value Analysis: Examined distributions of substances with similar H-statements across the full DOHSBase database
- Control Banding: Grouped chemicals based on hazards to suggest control measures, following internationally recognized banding principles
- Risk Management: Recognized as an effective strategy for handling chemical risks in the absence of formal OELs
- Cost Reduction: Minimizes the need for expensive health-based research by providing a statistically derived benchmark
- Proactive Approach: Helps organizations manage risks efficiently and systematically
- Workplace Safety: Provides interim guidelines for safer exposure limits, covering over 100,000 substances in DOHSBase Online
“The practicality and reliability of kick-off values have led to acceptance by regulatory bodies. Since 2012, the Dutch Labour Inspectorate (Inspectie SZW) has referenced DOHSBase’s methodology in guidelines for determining limit values, recognizing kick-off values as a valid tool for compliance with hazardous substance regulations.”