Benzyl chloride is a colorless to slightly yellow liquid characterized by its pungent, aromatic odor. This chemical compound is crucial to understand for safety in occupational settings, particularly concerning its Immediately Dangerous to Life or Health (IDLH) concentrations. This document provides a comprehensive overview of benzyl chloride, focusing on its IDLH value, toxicity data, and relevant safety guidelines.
What is Benzyl Chloride?
Benzyl chloride, identified by CAS number 100–44–7, is a chemical substance with notable industrial applications. It presents as a colorless to slightly yellow liquid and is easily recognizable due to its strong, aromatic, and somewhat irritating odor. Understanding its properties and hazards is paramount for professionals working in environments where exposure is possible.
Key Physical Properties:
- Appearance: Colorless to slightly yellow liquid
- Odor: Pungent, aromatic
Immediately Dangerous to Life or Health (IDLH) Concentration
The Immediately Dangerous to Life or Health (IDLH) concentration for benzyl chloride is 10 ppm (parts per million). This value, established by NIOSH (National Institute for Occupational Safety and Health), represents the maximum airborne concentration from which an unprotected individual could escape within 30 minutes without escape-impairing symptoms or irreversible health effects.
Basis for IDLH Value
The original and revised IDLH value for benzyl chloride remains at 10 ppm. This determination is based on early human studies noting the acute effects of inhalation:
- Intolerable Exposure: Exposure to 16 ppm was reported as intolerable to humans within just one minute [Flury and Zernik 1931].
- Irrespirable Atmosphere: A concentration of 20 ppm is considered to render the atmosphere irrespirable within one minute [ILO 1972].
- Immediate Irritation: Exposure to concentrations between 10 to 19 ppm immediately causes weeping and twitching of the eyelids. At 30 ppm, the effects become intolerable to the eyes and nasal mucous membranes [ILO 1971].
The IDLH of 10 ppm is set to ensure worker safety by providing a significant margin below concentrations that cause immediate and severe irritation, thereby facilitating safe escape in case of respiratory protection failure.
Acute Toxicity Data
Understanding the acute toxicity of benzyl chloride is crucial for assessing potential health risks. Data from animal studies and human observations provide a clear picture of its hazardous nature.
Lethal Concentration Data:
Animal studies provide quantitative data on the lethal concentrations (LC50) of benzyl chloride. LC50 refers to the concentration of a substance that is lethal to 50% of a test animal population within a specific time frame.
| Species | Reference | LC50 (ppm) | LCLo (ppm) | Time | Adjusted 0.5-hr LC (CF) | Derived value (ppm) |
|---|---|---|---|---|---|---|
| Rat | IARC 1976 | 150 | — | 2 hr | 240 ppm (1.6) | 24 |
| Mouse | IARC 1976 | 80 | — | 2 hr | 128 ppm (1.6) | 13 |
| Dog | NIOSH 1978 | — | 380 | 8 hr | 950 ppm (2.5) | 95 |
Note:
- LC50: Lethal Concentration, 50%
- LCLo: Lowest Lethal Concentration
- CF: Conversion Factor used to adjust for a 0.5-hour exposure duration.
These data indicate that benzyl chloride is acutely toxic via inhalation across different species. The adjusted 0.5-hr LC values provide a standardized measure for comparison and risk assessment over a shorter exposure period.
Other Animal Data:
Further studies, such as RD50 (concentration causing a 50% reduction in respiratory rate) in mice, show a sensory irritation level at 17 ppm [DeCeaurriz et al. 1981]. This reinforces the irritant properties of benzyl chloride even at concentrations near the IDLH value.
Human Data:
Human experiences and case reports corroborate the animal toxicity data:
- Intolerable at 16 ppm (1 minute): As mentioned earlier, exposure for just one minute at 16 ppm is reported as intolerable [Flury and Zernik 1931].
- Immediate Effects (10-19 ppm): Exposure within the range of 10 to 19 ppm leads to immediate symptoms such as weeping and twitching of the eyelids, indicating significant irritation even at low concentrations [ILO 1971].
Exposure Limits and Guidelines
To protect workers from the adverse effects of benzyl chloride exposure, various organizations have established exposure limits and guidelines. These include:
- NIOSH REL (Recommended Exposure Limit): 1 ppm (5 mg/m3) Ceiling (15-minute) – This is the NIOSH recommended maximum concentration for any 15-minute period.
- OSHA PEL (Permissible Exposure Limit): 1 ppm (5 mg/m3) TWA (Time-Weighted Average) – This is the current OSHA permissible exposure limit as an 8-hour time-weighted average.
- 1989 OSHA PEL: Same as the current PEL (1 ppm TWA).
- 1993-1994 ACGIH TLV (Threshold Limit Value): 1 ppm (5.2 mg/m3) TWA – The ACGIH TLV represents the concentration to which it is believed that workers can be exposed day after day without adverse health effects.
These exposure limits are designed to minimize the risk of both acute and chronic health effects associated with benzyl chloride exposure in occupational settings.
Conclusion
Benzyl chloride is a hazardous chemical with a low IDLH value of 10 ppm, underscoring its potential for causing immediate and severe health effects at relatively low concentrations. The established exposure limits by NIOSH, OSHA, and ACGIH highlight the importance of stringent safety measures and monitoring in workplaces where benzyl chloride is handled. Understanding the toxicity data and exposure guidelines is crucial for ensuring worker safety and preventing hazardous exposure incidents.
References
- ACGIH [1971]. Benzyl chloride. In: Documentation of the threshold limit values for substances in workroom air. 3rd ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, p. 24.
- DeCeaurriz JC, Micillino JC, Bonnet P, Guenier JP [1981]. Sensory irritation caused by various industrial airborne chemicals. Toxicol Lett 9(2):137–143.
- Flury F, Zernik F [1931]. Sch@dliche gase d@mpfe, nebel, rauch– und staubarten. Berlin, Germany: Verlag von Julius Springer, p. 339 (in German).
- IARC [1976]. IARC monographs on the evaluation of the carcinogenic risk of chemicals to man: benzyl chloride. Vol. 11. Lyon, France: World Health Organization, International Agency for Research on Cancer, p. 217.
- ILO [1971]. Benzyl chloride. In: Encyclopaedia of occupational health and safety. 2nd ed. Vol. I (A–K). Geneva, Switzerland: International Labour Office, pp. 169–170.
- ILO [1972]. Toluene and derivatives. In: Encyclopaedia of occupational health and safety. Vol. II (L–Z). 2nd ed. Geneva, Switzerland: International Labour Office, pp. 1414–1415.
- NIOSH [1978]. NIOSH criteria for a recommended standard: occupational exposure to benzyl chloride. Cincinnati,OH: U.S. Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 78–182.
