Chemical Exposure Limits

BREATHING RATE AND EXPOSURE LIMITS Did you know that an increased breathing rate may lead to overexposure? 🤔👇 Occupational exposure limits (OELs) are derived from No-Observed-Adverse-Effect-Level (NOAEL) or Lowest-Observed-Adverse-Effect-Level (LOAEL) values expressed as internal dose (mg/kg/day). Several uncertainty factors are then applied to these values to account for differences between study animals and humans. 🐀👨👩 The final value is then multiplied by the amount of inhaled air over the working day to arrive at mg/m3 (8-hour TWA) value. Most OELs are derived from the assumption that workers breathe in 10 m3 of air in 8 hours (20 litres/min). 🌬 For example, the UK Workplace Exposure Limit (WEL) for Silica (RCS) is 0.1 mg/m3 (8-hour TWA), which translates into 1 mg/day acceptable internal dose (0.1 mg/3 x 10 m3 = 1 mg/day). 💉 However, the breathing rate will vary significantly depending on gender, age, and level of physical exertion. According to Pleil et al. (2022), nominal values for normal human adult breathing at sea level can range from 6 l/min at rest to 140 l/min at high physical stress levels. 💨 As such, 8-hour exposure at 0.1 mg/m3 may result in significantly different internal doses at the end of the shift, depending on the level of physical activity. 💪 The internal dose may be x6.7 higher ❗❗❗ at high exertion levels than at normal/moderate activity levels, even though exposure levels remained the same. Therefore, it is essential to note any work factors that may increase the breathing rate during exposure assessment. ❗🕵♂️ It may not be easy to estimate the breathing rate precisely. Still, a rudimentary categorisation of the workload into “at rest”, “normal”, “moderate” and “stress” will help to identify scenarios where compliance with an OEL may not ensure actual health protection. ⛔ Do you routinely consider workload and breathing rate in your exposure assessments? Shall estimating the breathing rate become a standard practice in risk assessment? Share your thoughts and experiences in the comments. 🤔💡👇 〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰 If you enjoyed reading this week's post, please consider joining our #BitesizeOH community by following me here on LinkedIn. 🔗🙋♂️ I post FREE high-quality educational content about occupational hygiene in easy-to-digest pieces every Tuesday. ⏳🔔 Your support helps to spread the knowledge, so I appreciate your every like, comment, and reshare. 👍✍📢 Together, we can be the change! 🤝💪 〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰〰 Source: Pleil et al. (2022) The physics of human breathing: flow, timing, volume, and pressure parameters for normal, on-demand, and ventilator respiration.

Part 6 For junior HSE Hydrogen Sulfide (H₂S): Guidelines for Occupational Safety and Health Engineers Hydrogen sulfide (H₂S) poses a significant hazard in industries such as oil and gas, chemical manufacturing, and wastewater treatment. Occupational safety and health engineers must address the following aspects: 1. Physical and Chemical Properties and Risks • Flammability: Flammable gas with an explosive range of 4.3%–45.5% by volume in air. • Toxicity: Extremely hazardous at high concentrations. Maximum permissible exposure limits (MPEL) in the workplace: • Average shift concentration: 10 mg/m³. • Maximum single concentration: 15 mg/m³. • Cumulative effect: Chronic exposure can damage the respiratory and nervous systems. 2. Regulatory Standards Compliance with applicable regulations is essential, including: • GOST 12.1.005-88 – “General Sanitary Requirements for Workplace Air.” • Sanitary and fire safety rules governing work with toxic substances. • Equipment and process operation guidelines. 3. Risk Assessment The safety engineer must: • Analyze potential H₂S release sources. • Evaluate risks at each stage of the technological process. • Identify high-risk zones and establish restricted areas. 4. Prevention and Protective Measures Technical Measures • Ventilation systems: Use forced ventilation, especially in confined spaces. • Gas detectors: Install stationary or portable H₂S detectors with alarms. • Source isolation: Ensure equipment and pipelines are properly sealed. • Automation: Minimize manual work in hazardous areas. Organizational Measures • Conduct safety briefings. • Develop work instructions for handling H₂S. • Conduct emergency response drills. • Define zones where personal protective equipment (PPE) is mandatory. Personal Protective Equipment (PPE) • Respiratory protection: Gas masks with “K” filters (for H₂S) or self-contained breathing apparatus. • Eye protection: Sealed goggles. • Skin protection: Specialized protective clothing and gloves. 5. Emergency Response Signs of H₂S Leakage • Strong rotten egg odor. • Alarm activation by gas detectors. • Workers reporting eye irritation or dizziness. Response Protocol 1. Immediately evacuate personnel from the danger zone. 2. Notify emergency services and management. 3. Organize ventilation and isolate the leak. 4. If necessary, provide medical assistance. 6. Employee Training and Certification • Regular training on handling toxic and explosive substances. • Knowledge assessments of occupational safety requirements. • Practical training on PPE use and first aid for H₂S exposure.

Detailed Explanation of Impurity Thresholds and Fixing Limits The thresholds and procedures for setting impurity limits are defined primarily by ICH Q3A (R2) and ICH Q3B (R2) guidelines. 1. Thresholds of Impurities a. Reporting Threshold The level at which an impurity must be reported in the Certificate of Analysis (CoA) or regulatory submission. It ensures transparency in impurity monitoring. Example: For a drug substance with a maximum daily dose of 1 g, the reporting threshold is 0.05%. b. Identification Threshold The level at which an impurity must be chemically characterized to determine its structure and origin. This helps in understanding the potential sources of impurities (e.g., degradation, synthesis by-products). Example: For a drug substance with a daily dose ≤ 2 g, the threshold is 0.1%. c. Qualification Threshold The level above which the safety of an impurity must be assessed through toxicological studies. This ensures that the impurity does not pose significant risks to patients. Example: For a drug substance with a daily dose ≤ 2 g, the threshold is 0.15%. 2. Fixing Limits Based on Thresholds The limits of impurities are set using a combination of scientific, safety, and regulatory criteria. Below are the key steps: Step 1: Determine the Maximum Daily Dose (MDD) Calculate the highest dose of the drug likely to be consumed daily. Use this value to determine thresholds as defined in the ICH guidelines. Example: For a drug with an MDD of 500 mg: Reporting threshold: 0.05% (500 mg × 0.05% = 0.25 mg/day). Identification threshold: 0.1% (500 mg × 0.1% = 0.5 mg/day). Qualification threshold: 0.15% (500 mg × 0.15% = 0.75 mg/day). Step 2: Analytical Method Validation Develop and validate robust analytical methods (e.g., HPLC, GC, LC-MS) with appropriate sensitivity to detect and quantify impurities at the threshold levels. Ensure the methods meet the following criteria: LOD (Limit of Detection): Below the reporting threshold. LOQ (Limit of Quantification): Below or equal to the reporting threshold. Step 3: Identify the Source of Impurities Raw Materials and Synthesis: Identify starting materials and intermediates contributing to impurities. Degradation: Conduct stability studies to detect degradation products. Excipients: Evaluate excipient-related impurities in the formulation. Step 4: Toxicological Qualification If an impurity exceeds the qualification threshold: Conduct genotoxicity studies to rule out DNA damage. Perform toxicological evaluations, such as NOAEL (No Observed Adverse Effect Level) studies. Use a Threshold of Toxicological Concern (TTC) approach for impurities with unknown toxicity.

Testing Essentials for Work Permits Ensuring a safe work environment is critical when issuing work permits. Atmospheric conditions must be thoroughly tested for hazardous gases such as Oxygen (O₂), Hydrogen Sulfide (H₂S), Carbon Monoxide (CO), and Flammable Gases (LEL). Always use calibrated gas detectors prior to permit issuance. Continuous monitoring is mandatory in confined spaces. All personnel must be trained in gas hazards and emergency response. --- Oxygen (O₂) Normal level: 20.9% < 19.5%: Breathing apparatus required (OSHA 29 CFR 1910.146) > 23.5%: Work prohibited due to fire risk (NFPA 350) --- Hydrogen Sulfide (H₂S) 10 ppm: Breathing apparatus required (NIOSH REL) 20 ppm: Ceiling limit – Permissible Exposure Limit (OSHA 29 CFR 1910.1000) > 100 ppm: Immediate Danger to Life and Health (IDLH); work prohibited (NIOSH IDLH) --- Carbon Monoxide (CO) 35 ppm: Permissible Exposure Limit (PEL), 8-hour TWA (OSHA 29 CFR 1910.1000) 50 ppm: Threshold Limit Value (TLV), 8-hour TWA (ACGIH) > 1,200 ppm: Immediate Danger to Life and Health (IDLH); confined space entry prohibited (NIOSH IDLH) --- Flammable Gases (LEL – Lower Explosive Limit) > 0% LEL: No hot work allowed (NFPA 51B) 5–10% LEL: Breathing apparatus required (OSHA 29 CFR 1910.146) > 10% LEL: Work prohibited due to explosion risk (NFPA 69) --- Quick Reference – LEL of Common Gases Methane: ~5% Propane: ~2.1% Hydrogen: ~4%

Carbon monoxide did not go missing in Ontario. Last week, a workplace called me in confusion after they argued over why carbon monoxide exposure isn’t regulated. It is. Occupational Exposure Limits (OELs) exist to protect workers from overexposure and harmful effects of airborne chemicals, noise, heat stress, and more. Regulation 833 sets the law for over 700 chemical OELs in Ontario workplaces, but only about 100 are actually shown. If you can’t find a chemical there, then it’s important to check the OEL published in the 2017 ACGIH Threshold Limit Values booklet. If it’s not in the regulation but in the ACGIH TLV booklet, then that limit applies. About 600 OELs are not listed in Reg 833 but are found in the 2017 TLV booklet. A few examples include: - carbon monoxide - n-hexane - hexavalent chromium - sulfuric acid The Government of Ontario recently launched its 12-month Health & Safety Compliance Campaign. Inspectors will be focusing on enforcing Reg. 833 – Control of Exposure to Biological or Chemical Agents. Ontario publishes a separate table that shows the full list of all regulated chemical OELs. I refer to it often. I recommend that workplaces do the same because carbon monoxide is there.

🚦 Navigating Occupational Exposure Limits: How Do ECELs Compare to TLVs, PELs, and RELs? Industrial hygienists rely on Threshold Limit Values (TLVs) from ACGIH, Permissible Exposure Limits (PELs) from OSHA, and Recommended Exposure Limits (RELs) from NIOSH to assess risk. More recently, the EPA introduced Existing Chemical Exposure Limits (ECELs) under TSCA. But how do these standards compare? Understanding the Different Exposure Limits 🔹 TLVs: Health-based recommendations from ACGIH. 🔹PELs: Legally enforceable OSHA limits, often outdated. 🔹RELs: NIOSH recommendations based on current research. 🔹ECELs: New EPA guidelines under TSCA for chemical risk management. ⬇️ ⬇️ ⬇️ Example: Perchloroethylene (PCE) The proposed ECEL for PCE is far lower than other limits, indicating a stricter approach. Laboratory Detection and Respirator Considerations 🔹Sampling Methods: OSHA Method 1001 and NIOSH Method 1003. 🔹Detection Limits: Labs can detect PCE at 0.001 ppm. 🔹Respirator Cartridges: Organic vapor cartridges can filter PCE but require new change-out schedules under lower limits. The rise of ECELs suggests: 🔹More Frequent Updates with modern science. 🔹Stricter Workplace Controls requiring better monitoring. 🔹Cross-Agency Collaboration between OSHA, EPA, and NIOSH. While TLVs, PELs, and RELs have been standard, ECELs signal a shift in chemical risk management. Stricter limits will drive enhanced controls, improved PPE, and more precise exposure monitoring.

I still see workers exposing themselves daily to respirable crystalline silica dust without proper protection. OSHA has had strict limits in place for years, yet dry-cutting concrete without a respirator is still very common. The Permissible Exposure Limit (PEL) for silica is 50 micrograms per cubic meter (µg/m³) of air over an eight-hour shift. OSHA’s Action Level (AL) is just 25 µg/m³, which is like spreading an almost invisible layer of flour on a penny or dissolving a single drop of water into an entire swimming pool. Once exposure reaches this level, employers are legally required to start monitoring and implementing safety measures to protect workers. If you’re cutting concrete without a water system, dust collection, or at least a respirator, you’re potentially over the permissible exposure limit in just a matter of minutes or hours. From a medical perspective, breathing in silica dust can cause silicosis, lung cancer, COPD, kidney disease, and autoimmune disorders, with damage that is permanent and incurable. 

A NIOSH health hazard evaluation (HHE) report details the assessment of volatile organic compounds (VOCs), diacetyl, 2,3-pentadione, and carbon monoxide (CO), to workers where coffee was ground, roasted, and packaged. NIOSH collected air samples, installed a temporary ventilated enclosure around a large coffee grinder, and interviewed workers about their health concerns. Six out of seven personal air samples collected for employees involved with production tasks surpassed NIOSH’s recommended exposure limit (REL) for diacetyl, set at 5 ppb. The highest area concentrations of diacetyl, 2,3-pentadione, and CO were measured near the small coffee grinder. Diacetyl concentrations in this area ranged from 31.6 to 77.3 ppb. The 2,3-pentadione concentrations ranged from 22.8 to 50.5 ppb, exceeding NIOSH’s REL of 9.3 ppb for the substance. Although the report cautions that the results of area air sampling are not directly applicable to NIOSH RELs, area samples “can highlight areas with higher exposure risk, and the RELs can be used as points of reference.” Several full-shift continuous air measurements of CO collected near the small grinder exceeded NIOSH’s ceiling limit of 200 ppm. Peak CO measurements taken near the small grinder for each day of the survey ranged from 1,041 to 1,521 ppm. The latter, represented by a single 10-second measurement, surpassed NIOSH’s immediately dangerous to life and health (IDLH) value of 1,200 ppm. Personal and area air samples indicated that concentrations of diacetyl, 2,3-pentadione, and CO decreased after installing a ventilated enclosure to control emissions generated by a large coffee grinding machine. The roaster operators’ personal air samples decreased from 10.7 ppb to 8.8 ppb for diacetyl and from 7.8 ppb to 5.4 ppb for 2,3-pentadione. Measurements inside the enclosure compared with those outside indicated that the device reduced diacetyl and 2,3-pentadione concentrations by a factor of 16 and CO concentrations by 7 to 12-fold. As a temporary solution to control CO concentrations near the small grinder, a fan was positioned to blow emissions away from workers’ breathing zones during grinding tasks. This reduced the CO concentrations to just below NIOSH’s ceiling limit. However, the report warned that this conclusion was based on the results of one 17-minute sampling period and that the NIOSH ceiling limit for CO may still be exceeded, depending on factors such as coffee roast level or quantity. To more effectively control emissions near the small grinder, NIOSH recommended that a professional engineer design and install local exhaust ventilation and a CO monitor to alert employees if concentrations exceeded 200 ppm. If diacetyl and 2,3-pentadione exposures continued to surpass safe levels even after installing ventilation near the small grinder, NIOSH urged the employer to provide workers with respiratory protection. Ref: https://lnkd.in/eDKggRDE

EHS Lesson 𝗣𝗘𝗟, 𝗧𝗪𝗔, 𝗧𝗟𝗩, 𝗦𝗧𝗘𝗟, 𝗜𝗗𝗟𝗛, 𝗢𝗘𝗟 𝗮𝗻𝗱 𝗥𝗘𝗟 𝗣𝗘𝗟, 𝗧𝗪𝗔, 𝗧𝗟𝗩, 𝗦𝗧𝗘𝗟, 𝗜𝗗𝗟𝗛, 𝗢𝗘𝗟 𝗮𝗻𝗱 𝗥𝗘𝗟 are all related to occupational health and safety, particularly concerning exposure limits to hazardous substances in the workplace. 1. 𝗣𝗘𝗟 (𝗣𝗲𝗿𝗺𝗶𝘀𝘀𝗶𝗯𝗹𝗲 𝗘𝘅𝗽𝗼𝘀𝘂𝗿𝗲 𝗟𝗶𝗺𝗶𝘁): - This is the maximum amount or concentration of a chemical substance to which workers can be exposed over a specified period (usually 8 hours a day, 5 days a week) without adverse health effects. PELs are set by regulatory agencies like OSHA (Occupational Safety and Health Administration) in the U.S. 𝟮. 𝗧𝗪𝗔 (𝗧𝗶𝗺𝗲-𝗪𝗲𝗶𝗴𝗵𝘁𝗲𝗱 𝗔𝘃𝗲𝗿𝗮𝗴𝗲): - The TWA refers to the average concentration of a substance to which a worker can be exposed over a specific period, typically 8 hours (a full workday). It is used to ensure that exposure limits are not exceeded even if exposure is fluctuating throughout the day. 𝟯. 𝗧𝗟𝗩 (𝗧𝗵𝗿𝗲𝘀𝗵𝗼𝗹𝗱 𝗟𝗶𝗺𝗶𝘁 𝗩𝗮𝗹𝘂𝗲): - This is a guideline established by the American Conference of Governmental and Industrial Hygienists (ACGIH) for the airborne concentration of substances to which workers can be exposed over a specified period, typically an 8-hour workday. TLVs are not legally enforceable but are widely recognized and used in occupational health. 𝟰. 𝗦𝗧𝗘𝗟 (𝗦𝗵𝗼𝗿𝘁-𝗧𝗲𝗿𝗺 𝗘𝘅𝗽𝗼𝘀𝘂𝗿𝗲 𝗟𝗶𝗺𝗶𝘁): - The maximum concentration of a substance to which workers can be exposed for a short period (usually 15 minutes), without adverse effects. Typically, STELs are designed to limit short-term, high-level exposures. 𝟱. 𝗜𝗗𝗟𝗛 (𝗜𝗺𝗺𝗲𝗱𝗶𝗮𝘁𝗲𝗹𝘆 𝗗𝗮𝗻𝗴𝗲𝗿𝗼𝘂𝘀 𝘁𝗼 𝗟𝗶𝗳𝗲 𝗼𝗿 𝗛𝗲𝗮𝗹𝘁𝗵): - This is the concentration of a substance in the air that poses an immediate threat to life or health. It is used for emergency response situations where quick action is needed. 𝟲. 𝗢𝗘𝗟 (𝗢𝗰𝗰𝘂𝗽𝗮𝘁𝗶𝗼𝗻𝗮𝗹 𝗘𝘅𝗽𝗼𝘀𝘂𝗿𝗲 𝗟𝗶𝗺𝗶𝘁): - A general term referring to the limit of exposure to hazardous substances in the workplace. It includes PELs, TLVs, and other standards. 𝟳. 𝗥𝗘𝗟 (𝗥𝗲𝗰𝗼𝗺𝗺𝗲𝗻𝗱𝗲𝗱 𝗘𝘅𝗽𝗼𝘀𝘂𝗿𝗲 𝗟𝗶𝗺𝗶𝘁): - This is a guideline set by the National Institute for Occupational Safety and Health (NIOSH), recommending exposure limits for hazardous substances. RELs are similar to TLVs but are set based on NIOSH's scientific research and recommendations. 𝟴. 𝗢𝗦𝗛𝗔'𝘀 "𝗔𝗰𝘁𝗶𝗼𝗻 𝗟𝗲𝘃𝗲𝗹": - This is a concentration level set by OSHA, usually 50% of the PEL, at which employers must begin specific actions such as monitoring and implementing controls. 𝗖𝗼𝗻𝗰𝗹𝘂𝘀𝗶𝗼𝗻: These exposure limits are established to protect workers from health risks associated with chemicals and physical agents encountered in the workplace. They ensure that exposures remain within safe levels to prevent both acute and long-term health effects.

MATERIALS SAFETY ASBESTOS Asbestos is a naturally occurring mineral celebrated for its heat resistance and insulating properties, which led to its widespread use in construction and manufacturing throughout the 20th century. However, when asbestos-containing materials are disturbed, they release microscopic, needle-like fibers into the air. DANGEROUS EFFECTS ON HUMAN HEALTH The primary danger of asbestos lies in its ability to be inhaled or ingested. Once lodged in the respiratory or digestive tissues, these fibers are nearly indestructible by the body, leading to irritation, inflammation, and scarring over decades. This prolonged exposure is the cause of several devastating, slow-developing diseases, with symptoms often appearing 10 to 40 years after initial exposure: 1. Mesothelioma: A rare and aggressive cancer that affects the thin lining of the lungs, abdomen, or heart. It is almost exclusively linked to asbestos exposure. 2. Asbestosis: A chronic, non-cancerous lung disease where lung tissue becomes scarred (fibrosis), leading to severe shortness of breath, chronic cough, and a reduction in lung function. 3. Lung Cancer: Asbestos significantly increases the risk of lung cancer, particularly for individuals who also smoke, where the risk is dramatically compounded. CURRENT BAN AND WORKPLACE REGULATIONS While many countries have enacted complete bans, asbestos is not universally banned in the United States, although its use is highly regulated. The regulatory framework focuses on controlling exposure rather than a total prohibition on all products. Permissible Exposure Limits (PEL) The Occupational Safety and Health Administration (OSHA) enforces strict rules to protect workers. The federal PEL for asbestos is 0.1 fiber per cubic centimeter of air as an 8-hour time-weighted average (TWA). Employers must implement engineering controls (like ventilation) and provide personal protective equipment (PPE) to ensure exposures do not exceed this limit. Recent Bans In a significant 2024 rule, the U.S. Environmental Protection Agency (EPA) finalized a ban on the last remaining commercial use of chrysotile asbestos (the only form still being imported), although some industries have a multi-year phase-out period. Workplace Management Regulations mandate that employers identify the presence of Asbestos-Containing Materials (ACM), establish "regulated areas" for any work that could disturb asbestos, conduct routine air monitoring, and provide extensive training and medical surveillance for exposed workers.