Particularly Hazardous Substances (PHS) are a subset of chemicals recognized by the Occupational Safety and Health Administration (OSHA) as potentially harmful to the health of workers who handle them. Both short- and long-term health effects may occur following exposure to these chemicals, including nausea, stomach pain, vomiting, skin rashes, and even cancer or reproductive problems.

PHS can be found in a broad range of industries and occupational roles. To mitigate employee risk and ensure your workforce remains in compliance with all regulations and protocols, it's essential to understand what these chemicals are, what personal protective equipment (PPE) needs to be worn while working with these substances, and how to properly handle and store them.

What Are Particularly Hazardous Substances? 

Currently, OSHA recognizes three categories of PHS: carcinogens, reproductive toxins, and chemicals with a high degree of acute toxicity. These PHS are also recognized by other agencies, including Prop 65 (Chemicals Known to the State of California to Cause Cancer or Reproductive Toxicity), the National Toxicology Program (NTP), and the Environmental Protection Agency (EPA) as extremely hazardous substances.

In addition to the following three PHS categories, there are many novel chemicals used in research labs that have yet to be specifically tested for their potentially harmful properties and their short- and long-term effects on human health. For this reason, these chemicals should be regarded as particularly hazardous substances and treated as such.


Carcinogens are substances known to cause cancer in humans, or are considered capable of causing cancer in humans, because they are known to cause cancer in animals. These substances include known carcinogens regulated by OSHA and the International Agency for Research on Cancer (IARC). Under IARC, carcinogens can be further classified as Group 1 (“carcinogenic to humans”), Group 2A (“probably carcinogenic to humans”), or Group 2B (“possibly carcinogenic to humans”).

Common carcinogens include asbestos, methyl chloromethyl ether, 4-Nitrobiphenyl, benzidine, benzene, cadmium, methylene chloride, vinyl chloride, inorganic arsenic, formaldehyde, ethylene oxide, and coke oven emissions.

Reproductive Toxins

Reproductive toxins are substances known to cause genetic damage (mutagens), chromosomal damage, and/or lethal and physical defects in developing fetuses or embryos. OHSA currently regulates four agents as reproductive toxins, including dibromochloropropane (DBCP), lead, ionizing radiation, and ethylene oxide.

Chemicals with a High Degree of Acute Toxicity

Chemicals with a high degree of toxicity, also known as acutely hazardous materials, are ones that can cause a rapid harmful effect even after a single and brief exposure. The effect can be local to specific tissues and organs or widespread throughout the body (systemic). In severe cases, chemicals with a high degree of toxicity can be fatal.

Several classifications of this category exist based on animal testing. These classifications include "highly toxic" and "toxic."

"Highly toxic" chemicals are categorized by the following routes of exposure (oral, skin contact, or inhalation):

  • Having a median lethal dose (LD50) of 50 milligrams or less per kilogram of body weight when administered orally.
  • Having an LD50 of 200 mg or less per kg of body weight when administered by continuous contact for 24 hours, or less if death occurs within 24 hours.
  • Having a median lethal concentration (LC50) in air of 200 parts per million (ppm) by volume or less of gas or vapor, or 2 mg per liter or less of mist, fume, or dust by continuous inhalation for one hour.

"Toxic" chemicals have an oral LD50 of 50 to 500 mg/kg, skin contact LD50 of 200 to 1,000 mg/kg, vapor inhalation LC50 of 200 to 2,000 ppm, and dust, mist, or fume inhalation LC50 of 2 to 20 mg/liter.

Hydrogen cyanide, hydrogen sulfide, nitrogen dioxide, chlorine, diobrane gas, hydrogen fluoride, nickel carbonyl, ozone, phosgene, sodium azide, sodium cyanide, and arsine are common examples of chemicals with a high degree of acute toxicity.

What Industries Work With PHS?

A wide range of industries work with PHS. This includes laboratory, manufacturing, industrial, cleanroom, fire, plumbing, oil and gas, environmental remediation, power, healthcare, waste-water (blackwater), refining, pulp and paper, HVAC, and pharmaceutical. Workers within each industry must understand the specific safety and handling procedures for these substances, and employers must ensure that appropriate steps are taken to protect employees.

Information about PHS can be found within resources including:

  • Safety Data Sheets (SDS)
  • OSHA Laboratory Standard
  • Registry of Toxic Effects of Chemical Substances (RTECS)

As an employer, it's your responsibility to ensure access to this information is readily available for your employees.

Important Handling, Storage, and Safety Information About PHS

Knowing which types of PHS may be present in your occupational environment is an essential first step in protecting employees and reducing the risk of injury, disability, or even lethal harm. In addition, industries need to have clear safety procedures and measures in place to promote safer handling and storage.

Here are some important guidelines to consider if your industry is involved in handling and storing particularly hazardous substances:

  • When possible, potentially hazardous chemicals must be used and handled in specific and clearly identified areas. Storage areas for PHS must also be clearly defined and identified with hazard warning signs.
  • Ensure that all areas where PHS are handled have appropriate ventilation and lighting. Many hazardous substances require the use of explosive-proof electrical equipment.
  • Storage areas for PHS must be locked and secured when employees are not present.
  • Clear labeling must be used for any and all containers used for these materials—even if they contain only small quantities of the substance.
  • When necessary and able, containment devices like fume hoods should be used.
  • Personal protective equipment (PPE) must also be used whenever handling these substances.
  • Clear procedures for decontamination and clean-up of spills must be developed and strictly followed. Personnel should know what to do if they experience accidental ingestion, inhalation, or skin or eye contact. Employers should assume that any form of physical contact with PHS requires medical attention, and first responders or medical professionals should be provided with the substance's safety data information. Vomiting should not be induced for most types of PHS.
  • Only personnel who are trained to work with PHS should be permitted to handle this material or perform job duties that would potentially expose them to the substance, and only within designated areas.
  • In certain settings, such as laboratories, prior approval from a supervisor is required for the procurement and use of select PHS.
  • Only the minimum required amount of a given PHS should be used.
  • Establish a zero-tolerance policy for eating, drinking, chewing gum, or using cosmetics or utensils when handling PHS.
  • Ensure personnel thoroughly wash hands and arms immediately before and after handling any PHS and always maintain appropriate industrial hygiene standards.

Common Types of PPE Used for Particularly Hazardous Substances

Personal protective equipment (PPE) is essential for reducing the risk of employees who handle PHS. No matter what type of PPE your employees need, the equipment should be manufactured to meet industry standards and regulations for protection. Ideally, you'll also offer your employees PPE that is comfortable to wear and durable enough to avoid tears, rips, and other types of damage which could impair the integrity of the equipment and increase the risk of exposure.

Common PPE required for use of chemical hazards includes:

  • Safety goggles (for PHS, goggles that fit tightly against the face are often required, although detachable side shields worn on prescription eyeglasses may also be utilized).
  • Aprons
  • Jumpsuits
  • Lab coats
  • Long pants
  • Gloves
  • Face shields
  • Face masks
  • Full or half-face respirators
  • Closed-toe shoes
  • Shoe covers

Information about the specific type and material of PPE needed for chemical hazards can be found on the substance' SDS. For example, PPE for individuals handling the PHS ammonia should contain anti-static properties to minimize the risk of injury.

All employees must also be trained in how to properly don and doff PPE. In the case of equipment such as respirators, employees should be fitted to ensure appropriate use.

In many situations, disposable PPE for chemical hazards is required and preferable. This is because disposable protective equipment can promote enhanced containment and reduce the risk of contamination. For example, employees can safely dispose PPE onsite instead of having to transfer it or clean it.


Protecting employees from particularly hazardous substances is a top priority for employers within a range of industries, including pharmaceutical, laboratory, and manufacturing. PHS includes a large list of chemicals that are suspected or known to cause cancer, reproductive toxicity, or acute toxicity. In some cases, severe or even lethal injuries can occur after even a single and short-duration exposure.

As an employer, it is imperative that you establish and maintain strict safety and handling procedures for your employees who may interact with PHS within their typical and expected job duties. Employees must always be provided with appropriate PPE for hazardous substances and know how to don, doff, clean, store, and/or dispose of this PPE correctly.

Do you need help procuring the correct PPE for your employees who handle PHS? Contact International Enviroguard today to learn about our high-quality disposable PPE solutions.

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