Mineral-based hydraulic fluid

This toxicological profile discusses only three classes of hydraulic fluids mineral oil hydraulic fluids, polyalphaolefin hydraulic fluids, and organophosphate ester hydraulic fluids. The classes are based on the major chemicals found in the hydraulic fluids. However, hydraulic fluids are often complex mixtures of many chemical components. A particular hydraulic fluid can differ in... 

No studies were located that examined the toxicokinetics of mineral oil, organophosphate ester, or polyalphaolefin hydraulic fluids in humans or animals, with the exception of a study examining absorption in rats after exposure to a hydraulic fluid containing 99.9% cyclotriphosphazene (Kinkead and Bashe 1987) and the absorption and metabolism of Reolube HYD46, another organophosphate hydraulic fluid (Ciba-Geigy 1985). This section, therefore, discusses available information on the toxicokinetics of major components of these classes of hydraulic fluids or of materials that maybe expected to display similar toxicokinetic properties based on similar physical and chemical characteristics. It should be emphasized that many hydraulic fluids are complex mixtures of chemicals that may include some chemicals which may not share toxicokinetic properties with the major components. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding absorption in humans or animals after inhalation exposure to polyalphaolefin hydraulic fluids or their major components. Based on physicochemical similarities with mineral oils (i.e., long-chain aliphatic hydrocarbons are predominant... 

Based on physical and chemical similarities between mineral oil and polyalphaolefins, oil accumulation in the lung (and subsequent lipoid pneumonia) may occur following the ingestion of polyalphaolefin hydraulic fluids due to aspiration, and that distribution of polyalphaolefins to the liver and fatty tissues may occur to some degree (see discussion for distribution of mineral oil hydraulic fluids). 

Mineral Oil Hydraulic Fluids. No human studies examining dermal end points were located. In animals, no information on dermal effects following inhalation or oral exposure were located. A number of mineral oil hydraulic fluids have been tested for acute dermal toxicity in rabbits. Signs of skin irritation have been observed following application of a naphthenic petroleum-based hydraulic fluid designated as MIL-H-5606... 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. The developmental toxicity data base is generally inadequate. No studies were located regarding developmental toxicity after exposure by any route to mineral oil hydraulic fluids or polyalphaolefin hydraulic fluids. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. The data bases regarding the toxicity of mineral oil and polyalphaolefin hydraulic fluids are very limited. Further toxicity testing may elucidate biomarkers of exposure for these classes of hydraulic fluids. 

Table 3-3 contains information regarding the chemical identity of principal components of hydraulic fluids. Trade names are included when the component constitutes 100% (or nearly 100%) of the product. Information has also been included for several representative types of mineral oil. It should be noted, however, that the term "mineral oil" encompasses a wide variety of petroleum-based products. Several phosphate esters used as hydraulic fluid additives are also included in Table 3-3. 

In the sections that follow, the data needs issues for the mineral oil and polyalphaolefin hydraulic fluids will be discussed first. This will be followed in each section by a discussion of issues regarding organophosphate ester-based products. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. Limited information about environmentally important physical and chemical properties is available for the mineral oil and water-in-oil emulsion hydraulic fluid products and components is presented in Tables 3-4, 3-5, and 3-7. Much of the available trade literature emphasizes properties desirable for the commercial end uses of the products as hydraulic fluids rather than the physical constants most useful in fate and transport analysis. Since the products are typically mixtures, the chief value of the trade literature is to identify specific chemical components, generally various petroleum hydrocarbons. Additional information on the properties of the various mineral oil formulations would make it easier to distinguish the toxicity and environmental effects and to trace the site contaminant s fate based on levels of distinguishing components. Improved information is especially needed on additives, some of which may be of more environmental and public health concern than the hydrocarbons that comprise the bulk of the mineral oil hydraulic fluids by weight. For the polyalphaolefin hydraulic fluids, basic physical and chemical properties related to assessing environmental fate and exposure risks are essentially unknown. Additional information for these types of hydraulic fluids is clearly needed. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. No literature was identified dealing with the bioavailability of chemicals in this category of hydraulic fluids. Because of this wide variation and the lack of any information in mammalian species, it is difficult to estimate bioavailability to humans. Additional research on the bioavailability of this category of hydraulic fluids would be valuable but may not be as high a priority as research on bioavailability issues for the phosphate ester-based hydraulic fluids. 

The most common hydraulic fluids are generally of three types mineral oil, polyalphaolefln (PAO, synthetic oil), or organophosphate ester-based with a... 

Mineral oil and PAO-based hydraulic fluids are generally not toxic. They are expected to be absorbed only to a limited extent by lungs, skin, and the GI tract. 

Hydraulic fluids are not likely to cause chronic toxicity or cancer as currently manufactured and used. Only one epidemiology study has been conducted for a mineral oil-based fluid, and there were no associations between exposure and cancer. The mineral oils used in hydraulic fluids are highly refined and not mutagenic or carcinogenic in animals. The same would be expected for PAOs. 

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