What You Should Know About Lubricant Toxicity

Michael C. Brown, Noria Corporation

What You Should Know About Lubricant Toxicity

The world of lubrication is filled with many and varied lubricant types, and not all of them should be treated in a cavalier manner. In fact, most lubricants should be handled with care and proper personal protective equipment (PPE). The base oils and additives that make up lubricants not only can have catastrophic effects on the environment, but they can also be toxic to your health.


Additive Type


Typical Compounds


Anti-wear and EP Agents

Reduce friction and wear, and prevent scoring and seizure

Zinc dithiophosphates, organic phosphates, acid phosphates, organic sulfur and chlorine compounds, sulfurized fats, sulfides and disulfides

Chemical reaction with metal surface to form a film with lower shear strength than the metal, thereby preventing metal-to-metal contact

Corrosion and Rust Inhibitors

Prevent corrosion and rusting of metal parts in contact with the lubricant

Zinc dithiophosphates, metal phenolates, basic metal sulfonates, fatty acids and amines

Preferential adsorption of polar constituent on metal surface to provide protective film or neutralize corrosive acids


Keep surfaces free of deposits

Metallo-organic compounds of sodium, calcium and magnesium-phenolates, phosphonates and sulfonates

Chemical reaction with sludge and varnish precursors to neutralize them and keep them soluble


Keep insoluble contaminants dispersed in the lubricant

Alkylsuccinimides, alkylsuccinic esters and Mannich reaction products

Contaminants are bonded by a polar attraction to dispersant molecules, prevented from agglomerating and kept in suspension due to the solubility of the dispersant

Friction Modifiers

Alter the coefficient of friction

Organic fatty acids and amides, lard oil, high-molecular-weight organic phosphorus and phosphoric acid esters

Preferential adsorption of surface-active materials

Pour Point Depressants

Enable lubricant to flow at low temperatures

Alkylated naphthalene and phenolic polymers, polymethacrylates, maleate/fumerate copolymer esters

Modify wax crystal formation to reduce interlocking

Seal Swell Agents

Swell elastomeric seals

Organic phosphates and aromatic hydrocarbons

Chemical reaction with elastomer to cause slight swell

Viscosity Modifiers

Reduce the rate of viscosity change with temperature

Polymers and copolymers of olefins, methacrylates, dienes or alkylated styrenes

Polymers expand with increasing temperature to counteract oil thinning


Prevent lubricant from forming a persistent foam

Silicone polymers, organic copolymers

Reduce surface tension to speed collapse of foam


Retard oxidative decomposition

Zinc dithiophosphates, hindered phenols, aromatic amines, sulfurized phenols

Decompose peroxides and terminate free-­radical reactions

Metal Deactivators

Reduce catalytic effect of metals on oxidation rate

Organic complexes containing nitrogen or sulfur, amines, sulfides and phosphites

Form inactive film on metal surfaces by complexing with metallic ions

Base Oil Types

Base oils are made up of five different groups, as designated by the American Petroleum Institute (API). These groups help identify base stocks in finished oil formulations to ensure the oil’s performance criteria are met.

Group I includes base oils that are acid-treated, solvent-refined and aromatic. These are lubricants with sufficient evidence of carcinogenicity to humans. Group I oils contain compounds called polycyclic aromatic hydrocarbons (PAHs), which can exist in more than 100 different combinations. PAHs occur naturally in the environment but can also be man-made. They are found in tar, coal and various edible oils. PAHs are impurities that have been left behind after the refining process and are the reason Group I oils are considered carcinogenic.

A polycyclic aromatic hydrocarbon structure

Group ll oils are described as being mildly hydrotreated. While no human data exists for these lubricants, animal data has indicated possible or probable carcinogenicity. Mild hydrotreating helps reduce the amount of carcinogenic PAHs but does not necessarily eliminate them. Increasing the temperature and pressure of hydroprocessing can eliminate carcinogenic compounds.

Group lll base oils are manufactured using the hydrotreatment process but are subjected to higher temperatures or processing times. These highly hydroprocessed or non-conventional oils have improved oxidation stability and low-temperature performance but still contain some impurities that cannot be removed. These lubricants are not classifiable as being carcinogenic to humans. They include base oils that are severely hydrotreated.

The API has classified synthetic engine oils made with polyalphaolefins (PAOs) as a special class of base stock. The term “synthetic” was originally used to refer to Group IV (PAOs) and Group V base stocks. Group IV is used to designate PAO synthetics. All other base stocks, including other synthetics and natural esters (vegetable oils) default into Group V.

Of the refining steps used in preparing lubricating oil base stocks from petroleum, only effective solvent extraction, severe hydrogenation or exhaustive fuming sulfuric acid treatment appear to be adequate in eliminating PAHs. Newly synthesized PAOs (Group IV base stocks) do not contain PAHs.

With few exceptions, Group V synthetic oils are chemically engineered base stocks that do not fall into any of the previous categories. They are typically esters, polyglycols and silicone. In this group, most of the attention has been placed on phosphate esters, which have shown the most potential to harm humans. Allergic reactions have been associated with products containing triphenyl phosphate, and a number of health effects have been observed in laboratory animals ingesting phosphate-ester flame retardants.

7 PAHs on the EPA’s Priority Chemical List

  1. Acenaphthene
  2. Acenaphtylene
  3. Anthracene
  4. Benzo(ghi)perylene
  5. Fluorene
  6. Phenanthrene
  7. Pyrene


Additives are chemical substances that are mixed within lubricants to enhance their performance. There are many different types of additives, and most have the potential to harm the human body. Some of the more popular additives are shown in the table above. The best way to combat additives is to minimize your exposure to them. Always limit contact between your skin and the lubricant.

62% of plants have not taken any steps to address the toxicity and safety concerns in lubricant formulations, based on a recent poll at MachineryLubrication.com


A lubricant’s material safety data sheet (MSDS) can enable you to understand the risks to humans, animals and the environment. Each section of the MSDS is numbered and should include the information needed to determine if the lubricant is toxic, as detailed below:

Section 1 - The identification section identifies the chemical on the MSDS as well as the recommended uses. It also provides essential contact information for the supplier.

Section 2 - Hazard(s) identification includes the chemical’s hazards and the appropriate warning information associated with those hazards.

Section 3 - The composition/information on ingredients section identifies the ingredient(s) included in the product, such as stabilizing additives and impurities. It also contains information on substances, mixtures and all chemicals where a trade secret is claimed.

Section 4 - The first-aid measures describe the initial care that should be given by untrained responders to an individual who has been exposed to the chemical.

Section 5 - The fire-fighting measures provide recommendations for fighting a fire caused by the chemical, including suitable extinguishing techniques, equipment and chemical hazards from fire.

Section 6 - The accidental release measures offer recommendations on the appropriate response to spills, leaks or releases, including containment and cleanup practices to prevent or minimize exposure to people, properties or the environment. This section may also include recommendations distinguishing between responses for large and small spills when the spill volume has a significant impact on the hazard.

Section 7 - The handling and storage section provides guidance on the safe handling practices and conditions for safe storage of chemicals, including incompatibilities.

Section 8 - The exposure controls/personal protection section indicates the exposure limits, engineering controls and personal protective equipment (PPE) measures that can be used to minimize worker exposure.

Section 9 - The physical and chemical properties section identifies physical and chemical properties associated with the substance or mixture.

Section 10 - The stability and reactivity section describes the chemical’s reactivity hazards and stability information. It is broken into three parts: reactivity, chemical stability and other.

Section 11 - The toxicological information identifies toxicological and health effects information or indicates that such data is not available. This includes routes of exposure, related symptoms, acute and chronic effects, and numerical measures of toxicity.

Section 12 - The ecological information provides information to evaluate the environmental impact of the chemical if it were released to the environment.

Section 13 - The disposal considerations offer guidance on proper disposal practices, recycling and reclamation of the chemical or its container, as well as safe handling practices.

Section 14 - The transport information includes classification information for shipping and transporting hazardous chemicals by road, air, rail or sea.

Section 15 - The regulatory information identifies the safety, health and environmental regulations specific for the product which are not indicated elsewhere on the MSDS.

Section 16 - The other information section indicates when the MSDS was prepared or when the last known revision was made. It might also state where the changes have been made to the previous version. You may wish to contact the supplier for an explanation of the changes.

Be sure to read the MSDS for all the lubricants you handle and heed the warnings and recommendations. In many cases, the amount of exposure to a chemical will determine the risks. Some chemicals can build up in the body, with their effects not evident until many years later.

To protect yourself from these potentially hazardous materials, create a barrier between you and the lubricant. Wear gloves and safety glasses as well as oil- or chemical-resistant boots. If possible, keep all exposed skin covered. Also, if the oil is misting, wear a mask or some sort of breathing apparatus. By using basic common sense and being informed about the risks, you can avoid many of the problems associated with lubricant handling.

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About the Author

Michael C. Brown is an industrial services technician with Noria Corporation. He has more than 20 years of experience in heavy manufacturing and holds Machine...