Evaluation of the suitability of COSHH Essentials for qualitative assessment of inhalation risk from chemical agents in perfume laboratories: a new perspective

International Journal of Occupational Safety and Ergonomics ISSN: 1080-3548 (Print) 2376-9130 (Online) Journal homepage: www.tandfonline.com/journals/tose20 Evaluation of the suitability of COSHH Essentials for qualitative assessment of inhalation risk from chemical agents in perfume laboratories: a new perspective Pilar Lorenzale Algarra, Agustín Sánchez-Toledo, Alejandro Guillen Riquelme, Juan José Agún-González & Raúl Aguilar-Elena To cite this article: Pilar Lorenzale Algarra, Agustín Sánchez-Toledo, Alejandro Guillen Riquelme, Juan José Agún-González & Raúl Aguilar-Elena (10 Nov 2025): Evaluation of the suitability of COSHH Essentials for qualitative assessment of inhalation risk from chemical agents in perfume laboratories: a new perspective, International Journal of Occupational Safety and Ergonomics, DOI: 10.1080/10803548.2025.2575603 To link to this article: https://doi.org/10.1080/10803548.2025.2575603 View supplementary material Published online: 10 Nov 2025. Submit your article to this journal View related articles View Crossmark data Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=tose20 INTERNATIONAL JOURNAL OF OCCUPATIONAL SAFETY AND ERGONOMICS (JOSE) https://doi.org/10.1080/10803548.2025.2575603 Evaluation of the suitability of COSHH Essentials for qualitative assessment of inhalation risk from chemical agents in perfume laboratories: a new perspective Pilar Lorenzale Algarraa, Agustín Sánchez-Toledo a,b, Alejandro Guillen Riquelme a, Juan José Agún-González aand Raúl Aguilar-Elena a aResearch Group on Occupational Risk Prevention and Occupational Health and Safety (GPRL), PREVION Chair of Occupational Risk Prevention (Cátedra PREVION de Prevención de Riesgos Laborales), Valencian International University (VIU), Valencia, Spain; bIndustrial and Electronic Engineering Division of the School of Engineering and Technology, International Rioja University (UNIR), Logroño, Spain ABSTRACT Objectives. Professionals in the perfume industry are routinely exposed to numerous chemical substances during olfactory evaluations, some of which may pose inhalation hazards. Existing qualitative risk assessment tools, such as Control of Substances Hazardous to Health (COSHH) Essentials, provide approximate estimates and may not be well suited to industries with highly specific exposure conditions like perfumery.This study evaluates the applicability and limitations of COSHH Essentials in perfume laboratories and proposes an improved qualitative framework tailored to perfumers’ exposure scenarios. Methods. A total of 626 substances from a perfumer’s palette were assessed using COSHH Essentials, which classifies substances into risk levels based on hazard, volatility and quantity. A complementary method incorporating molecular-level hazard analysis, exposure patterns, occupational exposure limits and conservative inhalation dose estimations was developed. Statistical agreement between both methods was examined using Cohen’s κ, and McNemar’s test assessed significant differences. Results. COSHH Essentials identified 76 hazardous substances, while the enhanced method identified 81 substances, including five additional requiring local exhaust ventilation. Agreement was moderate (κ=0.58; p=0.031). Conclusion. COSHH Essentials provides a useful baseline but lacks the specificity needed in industries with intentional close-range exposure. The enhanced method enables more precise, context-sensitive assessment and better protection in fragrance laboratories. KEYWORDS risk management; Control of Substances Hazardous to Health; perfume; fragrances; occupational health 1. Introduction The chemical industry relies on thousands of compounds, both synthetic and naturally derived, which are used across a wide range of sectors, including cosmetics and fragrances [1,2]. Within this context, perfume creation is a complex and highly specialized process. Fragrances are developed based on detailed sensory specifications provided by clients, often through competitive submissions from multiple companies. The formulation that best captures the desired effect and evokes the intended sensations is selected for production [3]. A typical perfume consists of a combination of aromatic chemicals, alcohol and water. Perfumers are responsible for developing formulas by selecting appropriate ingredients and determining their proportions. Laboratory technicians prepare these formulations, which are then evaluated through olfactory testing. Based on feedback, the composition is refined until the desired result is achieved [4]. Some of the substances used in perfume manufacturing are classified as carcinogenic, mutagenic, or toxic to reproduction (CMR). With an estimated 10,000 raw materials available and a vast number of potential formulations, the fragrance industry presents significant inhalation hazards. This concern is particularly relevant for female assessors of reproductive age, who are commonly involved in the olfactory evaluation process [5,6]. Tasks in perfume production can be divided into two main exposure categories. The first includes those with intentional exposure, e.g., perfumers and evaluators, whose tasks require CONTACT Juan José Agún-González [email protected] Supplemental data for this article can be accessed online at https://doi.org/10.1080/10803548.2025.2575603. direct and repeated inhalation of chemical substances. The second includes roles with unintentional exposure, e.g., compounders, who handle chemical substances without directly inhaling them [7]. To evaluate inhalation risks, both qualitative and quantitative assessment methods may be employed. While quantitative methods are considered more precise, qualitative tools serve as useful preliminary assessments, especially in the absence of environmental measurements. In certain situations, they can provide sufficient guidance for implementing control measures. Although skin contact is also a relevant issue – particularly due to the presence of numerous skin sensitizers – this study focuses exclusively on inhalation risks [8–10]. Qualitative models are designed to help occupational health and safety professionals conduct initial assessments of chemical exposure and determine the appropriate preventive actions. These models are especially useful during process design and in cases where occupational exposure limits (OELs) are not available [11]. The most common variables used in such models include the following: •the hazardous properties of the chemical agent; •the frequency and manner of use; •the quantity of the substance handled; •the volatility or dustiness of the substance; •the type of control measures in place. © 2025 Central Institute for Labour Protection – National Research Institute (CIOP-PIB) 2P. LORENZALE ALGARRA ET AL. Several tools exist to estimate exposure risks. Some, e.g., the Control of Substances Hazardous to Health (COSHH) Essentials model, estimate potential exposure without considering current control measures [10–13]. Others, such as the French Institut national de recherche et de sécurité (INRS) model, assess actual exposure under existing controls. Hybrid models like Stoffenmanager combine both approaches [12,13]. The COSHH Essentials method was originally developed to support small and medium-sized enterprises and occupational safety professionals in managing chemical risks, particularly inhalation hazards. It recommends control measures based on the predicted potential for exposure, rather than actual measured risk. One of its main strengths lies in its simplicity and practicality. It introduces the concept of control banding, a method for categorizing tasks based on the level of control required to keep risks to a minimum [14,15]. This methodology has been included in the European Union’s Practical Guidelines for the Chemical Agents Directive 98/24/EC [16]. COSHH Essentials assigns substances to one of four risk levels by evaluating the following: •the health hazard classification based on the ‘H-statements’ (related to inhalation only); •the potential for airborne exposure, determined by volatility or dustiness; •the amount of substance used. While the method offers a practical framework, its reliability is limited by the heavy reliance on safety data sheets (SDS), which may contain incomplete or inconsistent hazard information. It is therefore advisable to cross-reference H-statements with other databases, such as the European Chemicals Agency (ECHA) or GESTIS hazardous substances database, particularly in complex exposure scenarios. Despite its limitations, COSHH Essentials remains accessible and easy to use – even for nonspecialists – and does not require extensive data input [14,15]. In the absence of prior studies focused on this topic, the goal of the present research is to determine whether the COSHH Essentials method is suitable for assessing inhalation risks in perfume laboratories. Based on our findings, we propose an improved qualitative assessment model that more accurately reflects the specific exposure conditions found in this and comparable industries [17,18]. 2. Methods 2.1. Study area This study was conducted at a fragrance manufacturing facility in Spain. The production process involves three main occupational tasks: •perfumer – designs and programs fragrance formulas, and performs olfactory evaluations in collaboration with a sensory expert; •perfume evaluator – interprets and translates scents into abstract concepts, moods and emotional responses; •fragrance compounder – applies finalized fragrance blends to various consumer products (e.g., neutral shampoos or shower gels provided by clients). The first two tasks are performed in the fragrance development laboratory, while the compounder works primarily in product formulation. The evaluator, commonly known as ‘the nose’, works closely with the perfumer throughout the process [17,19–21]. Based on the nature and intensity of chemical exposure, two similar exposure groups (SEGs) were defined [22]: •Intentionally exposed workers (perfumer and evaluator): these professionals are directly and repeatedly exposed to volatile chemicals through olfaction, which is an intrinsic part of their work. Olfactory assessments are conducted both orthonasally and retronasally, typically by holding scent strips or vials close to the nose. Unlike conventional workplace scenarios, the inhalation source is located extremely close to the respiratory zone, resulting in brief but intense exposures. Standard air sampling techniques, which place sensors on the collar, are inadequate in this context due to the short duration and spatial specificity of exposure. •Unintentionally exposed workers (compounders): these workers handle fragrance ingredients during product formulation but do not actively perform olfactory evaluations. Their exposure occurs passively through ambient air and can generally be controlled with standard engineering measures such as general ventilation or personal protective equipment (PPE). This group is not the focus of the present study. 2.2. Selection of substances From the facility’s perfumer’s palette, a total of 626 chemical substances – including both naturally derived extracts (e.g., essential oils, absolutes) and synthetic aromatic compounds – were selected for evaluation. This palette represents the complete range of raw materials routinely available to perfumers during fragrance creation and assessment [6]. These substances include both naturally derived extracts and synthetic organic compounds, many of which are used in complex mixtures [20]. The first step in evaluating inhalation risk was to identify substances classified as hazardous based on criteria established in the Globally Harmonized System (GHS) under the Classification, Labelling and Packaging (CLP) Regulation, particularly those classified as CMRs or with inhalation toxicity labels. A complete list of relevant hazard statements is presented in Table 1[23]. The selection process was based on the following criteria: •Regular use in formulation and evaluation processes: only substances incorporated into fragrance formulas or used during olfactory evaluations in recent production cycles were included, ensuring that the assessment reflected current operational practices [17,19]. •Availability of hazard classification under the CLP Regulation/GHS: each substance had to possess a documented hazard classification according to the CLP Regulation, aligned with the GHS [23]. This information was obtained from SDS and cross-checked against the ECHA database [24]. •Exclusion of hazards unrelated to inhalation: compounds classified with hazards not relevant to inhalation risk – e.g., H304 (‘May be fatal if swallowed and enters airways’) – were excluded from the dataset to maintain the focus on airborne exposure risks [25,26]. INTERNATIONAL JOURNAL OF OCCUPATIONAL SAFETY AND ERGONOMICS (JOSE) 3 Table 1. Substances with the CMR hazard classification of the GHS of classification and labelling of chemicals under the CLP Regulation or those substances that are toxic by inhalation. H Phrase SGA/CLP Hazard Indication Category Pictogram H330 Fatal if inhaled. Acute toxicity (inhalation), categories 1 and 2 H331 Toxic if inhaled. Acute toxicity (inhalation), category 3 H332 Harmful if inhaled. Acute toxicity (inhalation), category 4 H335 May cause respiratory irritation. Specific target organ toxicity, single exposure, category 3, respiratory tract irritation H336 May cause drowsiness or dizziness. Specific target organ toxicity, single exposure, category 3, narcosis H334 May cause allergy or asthma symptoms or breathing difficulties if inhaled. Respiratory sensitization, category 1 H340 May cause genetic defects. Germ cell mutagenicity, categories 1A and 1B H341 Suspected of causing genetic defects. Germ cell mutagenicity, category 2 H350 May cause cancer. Carcinogenicity, categories 1A and 1B H351 Suspected of causing cancer. Carcinogenicity, category 2 H360 May damage fertility or the unborn child. Reproductive toxicity, categories 1A and 1B H361 Suspected of damaging fertility or the unborn child. Reproductive toxicity, category 2 H362 May harm children fed with breast milk. Reproductive toxicity, effects on or through lactation H370 Causes damage to organs. Specific target organ toxicity, single exposure, category 1 H371 May cause damage to organs. Specific target organ toxicity, single exposure, category 2 H372 Causes damage to organs through prolonged or repeated exposure. Specific target organ toxicity, repeated exposure, category 1 H373 May cause damage to organs through prolonged or repeated exposure. Specific target organ toxicity, repeated exposure, category 2 Note: CLP =Classification, Labelling and Packaging Regulation; CMR =Carcinogenic, Mutagenic or Reproductive toxicant; GHS =Globally Harmonized System of Classification and Labelling of Chemicals; H =Hazard statement code. Table 2. Assigned hazard groups for the first 20 substances. Name Phrase H Phrase H Phrase H Phrase H Phrase H Phrase H Phrase H Hazard Group A-E ACETYLPROPIONYLE NA H318 H317 H373B H303 H313 H316 C ACETYLPROPIONYLE NAT NA H318 H317 H373B H303 H313 H316 C ALDEHYDE BENZOIQUE H302 H332 H319 H335 NA H313 H316 C ALDEHYDE BENZOIQUE NAT US H302 H332 H319 H335 NA H313 H316 C ARMOISE HE NA H302 H315 H317 H319 H371 NA C BASILIC HE H302 H315 H320 H317 X H341B H351B E CAMPHRE NA H318 H302 H332 H315 H371 NA C CANNELLE SRI LANKA HE H312 H315 H317 H319 NA H303 H350B E CAPROATE D’ALLYLE H301 H311 H331 NA NA NA NA C CAPROATE D’ALLYLE NAT US H301 H311 H331 NA NA NA NA C CANNELLE FEUILLE HE H317 H319 NA H303 H316 H341B H350B E MAGNOLIA HE H315 H317 H319 NA H303 H341B H351B E MUSCADE HE H304 NA H317 H341B H350B NA NA E ROMARIN HE H304 NA H315 H317 H371 H303 NA C ROSE DAMASCENA HE H318 NA H315 H317 H303 H341B H351B E SAUGE DALMATE HE H304 H318 NA H302 H315 H317 H371 C Note: H =Hazard statement code; HE =Essential oil (from French Huile Essentielle); NA =Not applicable, NAT US =Natural origin (sample sourced from the United States). Each of the 626 substances was assessed using the COSHH Essentials methodology via an Excel-based database, where individual H-statements were identified and used to assign each substance to a specific risk category (Table 2). Following the hazard classification, the volatility of the 626 substances was evaluated using their boiling points, assuming a typical laboratory temperature of 25 °C. Laboratory technicians typically perform between 120 and 180 weighings per day. Depending on the complexity of the formula, each weighing operation can take between 1 and 3 min. The quantity of chemical substances used per operation ranges from as little as 0.1 g up to 50 g. Given these conditions, the quantity of each substance handled during routine procedures is classified as ‘small’ [27]. 4P. LORENZALE ALGARRA ET AL. Table 3. Volatility levels assigned to the first 20 substances. Name Boiling point Volatility ACETYLPROPIONYLE =110°C Medium ACETYLPROPIONYLE NAT =110°C Medium ALDEHYDE BENZOIQUE <40°C High ALDEHYDE BENZOIQUE NAT US <40°C High ARMOISE HE <40°C High BASILIC HE <40°C High CAMPHRE <40°C High CANNELLE SRI LANKA HE <40°C High CAPROATE D’ALLYLE =186°C low CAPROATE D’ALLYLE NAT US <40°C High CANNELLE FEUILLE HE <40°C High MAGNOLIA HE <40°C High MUSCADE HE <40°C High ROMARIN HE <40°C High ROSE DAMASCENA HE <40°C High SAUGE DALMATE HE <40°C High Note: °C=Degrees Celsius; HE =Essential oil (from French Huile Essentielle), NAT US =Natural origin (sample sourced from the United States). Following hazard identification, each of the 626 substances was assigned to a hazard group (A–E) based on the inhalationrelated H-statements. Volatility was determined from boiling points at 25 °C, and quantities handled were classified as ‘small’ (<50 g per operation) based on standard laboratory weighing practices. These parameters – hazard group, volatility and quantity – were then used to determine the COSHH Essentials risk level for each substance, ranging as follows: •risk level 1: manageable with general ventilation; •risk level 2: requires local exhaust ventilation; •risk level 3: requires enclosed or contained systems; •risk level 4: requires advanced, expert-designed control measures with quantitative exposure assessment. Complete results for the 626 substances, including hazard group, volatility, quantity and COSHH risk level, are provided in Supplementary Table S1. An excerpt for the first 20 substances is presented in Tables 2–4. All figures and statistical analyses, including Cohen’s κand McNemar’s test, were performed in R version 4.4.2 using RStudio 2025.05.0 Build 496 and the packages ggplot2, irr and stats. 3. Results Following the initial hazard assessment based on H-statements, it was observed that 75% of the 626 substances in the perfumer’s palette were not classified as posing any inhalation risk. An additional 13% carried the health hazard pictogram but were labeled solely with H304 (‘May be fatal if swallowed and enters airways’), which – as previously explained – pertains to ingestion-related aspiration risks rather than inhalation hazards. This distinction is important to prevent misinterpretation and undue concern among exposed workers. In addition, 4% of the substances were classified as CMRs. Among these, 2% were categorized as reproductive toxins (H360 and H361), indicating potential harm to fertility or fetal development. A further 1% were associated with acute toxicity Table 4. Risk level results for the first 20 substances. Name Hazard Group A-E Volatility Substance quantity Risk level ACETYLPROPIONYLE C Medium tiny 2 ACETYLPROPIONYLE NAT C Medium tiny 2 ALDEHYDE BENZOIQUE C High tiny 2 ALDEHYDE BENZOIQUE NAT US C High tiny 2 ARMOISE HE C High tiny 2 BASILIC HE E High tiny 4 CAMPHRE C High tiny 2 CANNELLE SRI LANKA HE E High tiny 4 CAPROATE D’ALLYLE C low tiny 1 CAPROATE D’ALLYLE NAT US C High tiny 2 CANNELLE FEUILLE HE E High tiny 4 MAGNOLIA HE E High tiny 4 MUSCADE HE E High tiny 4 ROMARIN HE C High tiny 2 ROSE DAMASCENA HE E High tiny 4 SAUGE DALMATE HE C High tiny 2 Note: HE =Essential oil (from French Huile Essentielle); NAT US =Natural origin (sample sourced from the United States). (categories 1, 2 and 3), and another 1% fell under acute toxicity category 4 and/or reproductive toxicity related to lactation (H362). Overall, 12% of the substances in the palette were identified as having potential inhalation risks under typical occupational exposure conditions. It is important to note, however, that consumer exposure is assessed through separate methodologies, which account for the significantly lower concentrations and smaller quantities present in finished products, ensuring their safe use. Using the COSHH Essentials method, the 626 substances were distributed across the four risk levels, with the majority showing no inhalation risk under typical occupational conditions. The detailed distribution is presented in Figure 1. The remaining 550 substances (87.85%) were not associated with inhalation risk and, for precautionary purposes, were conservatively considered as risk level 1 to safeguard worker health (see Figure 1). The results indicate that the COSHH Essentials method does not account for the distinct exposure patterns observed between the two categories of workers: those with intentional versus unintentional exposure. Additionally, the method does not consider the chemical composition of individual substances, focusing instead on general hazard classification. As shown in the results, COSHH Essentials groups substances into broad risk levels without differentiating the molecular characteristics that may significantly influence toxicological risk. Given these limitations, we propose an enhancement to the COSHH Essentials framework that integrates both chemicalspecific characteristics and the real-world exposure conditions of perfume laboratory workers (Figure 2). The first component of this proposed methodology, like the original COSHH model, begins by identifying substances with H-statements linked to inhalation hazards. However, the enhanced approach goes further by identifying the specific INTERNATIONAL JOURNAL OF OCCUPATIONAL SAFETY AND ERGONOMICS (JOSE) 5 Figure 1. Results of the COSHH Essentials method: number of substances by risk level. Note: COSHH =Control of Substances Hazardous to Health. Table 5. Comparison of risk levels between both methods. Method proposed COSHH 1 2 3 0 0 5 545 10113 22724 3 0 11 11 4016 Note: COSHH =Control of Substances Hazardous to Health. molecules within each substance responsible for the associated health risks. Rather than treating each substance as a homogeneous hazard, this method aims to pinpoint the toxicologically active components. For each substance, hazard assessment was performed at the molecular level, identifying the specific components responsible for inhalation-related health risks. When compositional data were unavailable, a conservative purity of 100% for the hazardous component was assumed. This means that risk calculations were conducted as if the evaluator was exposed to the pure hazardous compound, even when in practice it may be present at lower concentrations within a mixture. This approach differs from the COSHH Essentials method, which bases classification solely on the hazard statements provided in the SDS for the whole substance or mixture, without adjusting risk levels according to the concentration of hazardous constituents. By modeling risk at 100% purity, the developed method applies a more precautionary exposure estimate, potentially resulting in higher control requirements for substances containing hazardous components in significant but undeclared proportions. For instance, consider rose oxide (Chemical Abstracts Service [CAS]: 0016409431), which carries the hazard statement H361B (‘Suspected of damaging fertility or the unborn child (fetus, during pregnancy)’). In this case, rose oxide purity is present at 99.94%, making it the primary contributor to the associated risk. Similarly, in basil essential oil (CAS: 008015734), which presents H314B, H351B and H341 hazard statements, the main constituents are estragole (CAS: 0000140670) at 91% and eucalyptol (CAS: 0000470826) at 9%. The health hazard in this case is primarily attributed to estragole, which carries both H341 and H351B. These examples highlight the necessity of molecule-specific analysis, particularly for substances not explicitly labeled as CMR but which contain hazardous components. Therefore, the following steps should be taken: •retrieve the OELs for each substance and calculate tolerable intake levels for both an 8-h shift (time-weighted average [TWA]) and a 15-min short-term exposure limit (STEL); •estimate the inhaled dose per exposure event; •determine the maximum number of acceptable daily inhalations and interpret whether exposure conditions are within safe limits. During olfactory evaluations, substances are presented close to the evaluator’s nose either on scent strips moistened with the chemical or directly from an open 10-ml vial. In both cases, evaluators perform several short, shallow inhalations to perceive the aromatic profile. To maintain a conservative margin of safety, the following assumptions are applied: •the substance is considered to be pure and hazardous, regardless of its actual concentration in the mixture (e.g., 100% rose oxide); •the airspace surrounding the nose during evaluation is assumed to be fully saturated with the chemical vapor, even if only a small amount is present on the paper strip; •the distance from the nose to the source is conservatively estimated at 2 cm, defining a virtual inhalation zone This conservative approach ensures that safety margins remain high even under worst-case scenarios, allowing for a more precise and protective risk assessment tailored to the specific nature of olfactory exposure in the perfume industry [17] (Figure 3). When performing olfactory evaluations using vials, the headspace – the free volume within the neck of the container 6P. LORENZALE ALGARRA ET AL. Figure 2. Structured framework of the enhanced COSHH Essentials methodology integrating purity, inhaled dose and allowable inhalations for risk level assignment. Note: A step-by-step overview of the enhanced methodology developed in this study. The process begins with the identification of substances carrying H-statements related to inhalation hazards, followed by a molecularlevel hazard assessment that determines the active components and their purity (defaulting to 100% if unknown). Next, the inhaled dose is estimated based on a 35-ml virtual inhalation zone and the ideal gas law. This dose is compared to OELs, such as TLVs or DNELs, to calculate the maximum allowable number of inhalations per day. Where no OEL exists, alternative sources or read-across from toxicologically similar substances are used; in the absence of any reference value, the substance is conservatively assigned to the highest risk level. Finally, the adapted COSHH Essentials risk levels and corresponding control measures are assigned, ensuring a more sensitive and context-specific evaluation for perfume laboratory workers. Note: COSHH =Control of Substances Hazardous to Health; DNEL =derived no-effect level; OEL =occupational exposure limit; TLV =threshold limit value. Figure 3. Virtual vapor-saturated sphere (2-cm radius). (e.g., a 10-ml bottle) – is assumed to be saturated with vapors corresponding to the substance’s vapor pressure at ambient temperature [20]. To assess the inhaled dose, the following conservative assumptions are applied: •Absorption of 100% is assumed, meaning the entire quantity of substance inhaled is considered retained in the body. This simplification accounts for the wide variability in physicochemical properties that affect absorption and ensures a protective margin. •For standard workers, calculations are based on an average respiratory flow rate of 20 L/min or 1.2 m3/h, which corresponds to 9.6 m3of inhaled air per 8-h workday, as per the International Commission on Radiological Protection (ICRP) human respiratory tract model for radiological protection [28]. •For olfactory evaluators, the dose is calculated based on the volume of saturated headspace during scent evaluation. This dose is then compared to an acceptable threshold, derived by multiplying the OEL by the reference inhalation volume (9.6 m3). This approach ensures a standardized and conservative framework for risk assessment in this unique context [21]. While actual absorption varies – some substances may be largely exhaled, while others are extensively retained – data are lacking for most fragrance ingredients. As a result, this 100% absorption assumption, although likely overestimating risk in many cases, remains a cautious and protective standard. In summary, for any substance with potential inhalation hazards, we assume the following: •it is present in pure form (100%); •the air within a 35-ml virtual sphere (corresponding to a 2-cm distance from the evaluator’s nose to the sample) is saturated with vapors of the substance; •the entire inhaled dose is absorbed by the respiratory system. Using this assumption, if a perfumer or evaluator inhales air from a 35-ml volume, the amount of substance inhaled per breath (in milligrams or parts per million) can be estimated using the ideal gas law. Exposure limits such as threshold limit values (TLVs) or derived no-effect levels (DNELs) exist for approximately 1800 substances. These values, while varying between regulatory authorities, are designed to protect workers under continuous daily exposure. In contrast, exposure during olfactory evaluations is brief and intermittent, and therefore significantly lower. To contextualize exposure: •STELs – typically based on 15-min periods – are applied. •Based on the daily inhaled volume (9.6 m3) and relevant TLVs, the maximum tolerable daily dose is calculated. •From this value, the maximum allowable number of inhalations per day can be determined. •For substances with established OELs, including TLVs, DNELs or equivalent values from other regulatory bodies, the maximum allowable number of inhalations per day is calculated by dividing the tolerable daily dose by the estimated dose per inhalation. INTERNATIONAL JOURNAL OF OCCUPATIONAL SAFETY AND ERGONOMICS (JOSE) 7 Figure 4. Results of the proposed method: number of substances by risk level. •When no OEL or equivalent value is available, alternative sources are consulted (e.g., National Institute for Occupational Safety and Health [NIOSH] recommended exposure limits or American Industrial Hygiene Association [AIHA] workplace environmental exposure levels) or read-across is performed using toxicologically similar substances. In the absence of any reference value, a conservative approach is adopted, automatically assigning the substance to the highest control category to ensure worker protection. This allows the method to be applied to all substances in the dataset, while maintaining a precautionary bias for those without established exposure limits. To account for cumulative exposure, a safety margin was established based on consultations with professional evaluators. Feedback indicated that it is uncommon for a single substance to be inhaled more than 20 times per day. To maintain a conservative estimate, 100 inhalations per day was adopted as a protective threshold. Risk classification is then based on the following criteria: •If the number of inhalations required to exceed the tolerabledoseis >100, the substance is considered safe under typical use conditions. •If the number of inhalations to exceed the dose is ≤100, the substance is classified as potentially hazardous, and a more detailed evaluation is required. In these cases, an advanced model – based on the universal functional activity coefficient (UNIFAC) method – can be used to determine the maximum safe concentration of the substance in a solvent (e.g., ethanol or D-limonene) to ensure safety at 100 inhalations per day or six inhalations over a 15min period. If the activity coefficient is <1, the substance tends to remain dissolved (lower volatility and lower risk); if >1, it favors evaporation, increasing the inhalation risk for workers [21]. Based on the results of this improved analysis, the 626 substances were classified into three control groups according to their associated risk level: •control group 1: two substances requiring high containment measures, such as use inside a fume hood with localized ventilation; •control group 2: 22 substances requiring localized exhaust ventilation, such as push–pull systems; •control group 3: 52 substances that can be handled under general ventilation, assuming no recirculation and 100% air renewal. These findings support a more tailored and accurate approach to risk control and help guide the selection of preventive measures based on the actual exposure characteristics of each substance (Figure 4). The comparison between the COSHH Essentials method and the proposed model revealed notable discrepancies in the identification of hazardous substances, with no consistent pattern observed. In some instances, both methods assigned similar risk levels; in others, COSHH Essentials classified the risk as higher. However, the proposed model – grounded in molecular-level analysis and practical experience in the chemical industry – provided a more nuanced risk characterization. Using the enhanced approach, 81 out of 626 substances were classified as potentially hazardous, compared to 76 substances identified by the COSHH Essentials method, which relies primarily on hazard statements (H-statements). Notably, the improved model flagged five additional substances that required local exhaust ventilation, which were not detected by the COSHH Essentials method. This divergence suggests that COSHH Essentials, while useful for general screening, may underestimate specific risks when it fails to consider molecular composition or contextual exposure parameters. To quantify the agreement between both approaches, classification results for all 626 substances were compared using Cohen’s κcoefficient. The unweighted κwas –0.007 (p=0.003) and the weighted κwas –0.021 (p<0.001), both values indicating poor agreement between the two methods. Differences in classification proportions were tested using McNemar’s test for paired nominal data (χ2=556.0, p<0.001), which confirmed a highly significant systematic 8P. LORENZALE ALGARRA ET AL. difference. This divergence was mainly driven by 564 substances classified as low risk by COSHH Essentials (levels 0–1) but as high risk ( ≥2) by the developed method, whereas only two cases occurred in the opposite direction. These results support the conclusion that the developed method systematically identifies additional cases requiring higher-level control measures compared with COSHH Essentials. These findings underscore the limitations of relying solely on H-statements for chemical risk assessment. The very low κvalues (κ≈0) indicate poor agreement between COSHH Essentials and the developed method, while McNemar’s test confirmed a highly significant systematic difference driven by the reclassification of 564 substances from low risk (levels 0–1 in COSHH Essentials) to high risk ( ≥2) under the proposed framework. By contrast, the developed method exhibits greater sensitivity in identifying potential inhalation hazards, ensuring that substances underestimated by COSHH Essentials are more conservatively managed. Nevertheless, it is important to acknowledge that this approach requires further validation through empirical exposure measurements, which will be conducted in future studies to confirm its robustness and practical applicability. In conclusion, the results highlight the need for a more detailed, context-specific, and molecule-based risk assessment framework, as proposed in this study, to provide a more comprehensive and protective evaluation of chemical hazards in perfume laboratories and comparable occupational settings. 4. Discussion and conclusions The COSHH Essentials method provides a practical and accessible framework for the preliminary assessment of inhalation risks in occupational settings. However, its applicability is limited in specialized environments such as perfume laboratories, where intentional, repeated and close-range inhalation of volatile substances is a routine part of the work process. COSHH Essentials categorizes substances based on general risk levels using hazard statements (H-statements), volatility and quantity used, but does not account for the unique exposure patterns of perfumers and evaluators, and neither does it consider the molecular composition of individual substances. The approach proposed in this study addresses these limitations by incorporating the following: •molecular-level hazard identification of active compounds; •conservative dose estimation assuming worst-case exposure scenarios; •exposure assumptions aligned with real working conditions in fragrance development. This refined methodology identified five additional hazardous substances requiring local exhaust ventilation that were not detected by COSHH Essentials, demonstrating a higher sensitivity to potentially overlooked risks. These findings highlight the drawbacks of relying solely on H-statements for risk classification in industries characterized by direct olfactory exposure. These findings, consistent with the near-zero κvalues and the significant McNemar test results, demonstrate that the developed method is substantially more conservative than COSHH Essentials. While COSHH Essentials tends to classify many substances as ‘no risk’ or ‘minimal risk’, the developed method, by integrating molecular composition, purity assumptions and inhaled dose calculations, systematically upgrades these cases to higher risk levels requiring technical controls. This divergence highlights the limitations of COSHH Essentials in specialized contexts such as perfume laboratories, where intentional, close-range inhalation of concentrated volatiles is routine. The developed framework therefore provides a more precautionary and context-sensitive approach to protecting workers. An important methodological distinction between the developed approach and COSHH Essentials lies in the treatment of substance purity. COSHH Essentials classifies a substance or mixture based on the hazard statements listed in its SDS, which may already reflect dilution or low concentrations of hazardous constituents. In contrast, the developed method assumes a conservative purity of 100% for the hazardous component when compositional data are unavailable. This worst-case scenario ensures that risk calculations are based on the maximum possible exposure to the toxicologically active molecule, regardless of its actual concentration in the mixture. By applying this assumption, the developed method increases sensitivity in detecting potentially underestimated risks. This conservative approach can result in higher assigned control measures for substances containing hazardous constituents at significant, but undeclared, concentrations. This difference in risk estimation likely explains the five additional substances identified by the developed method as requiring local exhaust ventilation, which were not flagged by COSHH Essentials. In occupational settings where exposure is intentional, repeated and close to the respiratory zone – such as perfume laboratories – this added precaution enhances worker protection beyond that provided by generic qualitative models. While both methods ultimately suggest that most substances in the perfumer’s palette present low inhalation risks under controlled conditions, the enhanced model offers greater precision in distinguishing between acceptable and potentially hazardous scenarios. Furthermore, it explicitly differentiates between intentional and unintentional exposure groups, a distinction often neglected in generalized models but crucial in fragrance manufacturing. Overall, the results of this study emphasize the need for more tailored and context-sensitive tools in qualitative chemical risk assessment – particularly in sectors involving shortduration, high-frequency exposure to complex mixtures. The proposed method contributes both strategic and preventive value for occupational health professionals by facilitating more accurate evaluations and the implementation of appropriate control measures. Future research will aim to validate this methodology through empirical exposure measurements, enabling refinement of its assumptions and enhancing its predictive capacity in real-world applications. 4.1. Strengths and limitations This new qualitative assessment model presents several notable strengths: •Assessment of chronic inhalation exposure: the model incorporates 8-h time-weighted average OELs, enabling evaluation of long-term health risks. These thresholds are associated with chronic conditions that are dosedependent, making them well suited for assessing cumulative exposure during repeated olfactory testing.