Subchronic and developmental toxicity of aromatic extracts.

Aromatic extracts (AEs; distillate AEs [DAEs] and residual AEs [RAEs]) are complex, highly viscous liquid petroleum streams with variable compositions derived by extraction of aromatic compounds from distillate and residual petroleum fractions from a vacuum distillation tower, respectively. The DAEs generally contain significant amounts of polycyclic aromatic compounds (PACs) and are carcinogenic. The RAEs typically contain lower concentrations of biologically active PACs. The PACs in refinery streams can cause effects in repeated-dose and developmental toxicity studies. In a 13-week dermal study, light paraffinic DAE had several dose-related effects involving multiple organs; no-observed-effect level was <5 mg/kg/d, with no overt toxicity. Predicted dose-responses at 10% (PDR10s), modeled doses causing a 10% effect on sensitive end points based on PAC content, ranged from 25 to 78 mg/kg/d for untested paraffinic DAEs. The no observed adverse effect level (NOAEL) for developmental toxicity for light paraffinic DAE was 5 mg/kg/d. Statistically significant developmental effects at higher doses were associated with maternal effects. The PDR10s for developmental toxicity of paraffinic DAEs ranged from 7 to >2000 mg/kg/d, reflecting differences due to variation in PACs. The NOAELs for RAEs were 500 mg/kg for 90-day studies and 2000 mg/kg for developmental toxicity. Reproductive toxicity is not considered to be a sensitive end point for AEs based on the toxicity tests with DAEs, RAEs, and other PAC-containing petroleum substances. In vivo micronucleus tests on heavy paraffinic DAE, RAEs, and a range of other petroleum substances have been negative. The exception to this general trend was a marginally positive response with light paraffinic DAE. Most DAEs are considered unlikely to produce chromosomal effects in vivo.

Acute, subchronic, and developmental toxicological properties of lubricating oil base stocks.

Lubricating oil base stocks (LOBs) are substances used in the manufacture of finished lubricants and greases. They are produced from residue remaining after atmospheric distillation of crude oil that is subsequently fractionated by vacuum distillation and additional refining steps. Initial LOB streams that have been produced by vacuum distillation but not further refined may contain polycyclic aromatic compounds (PACs) and may present carcinogenic hazards. In modern refineries, LOBs are further refined by multistep processes including solvent extraction and/or hydrogen treatment to reduce the levels of PACs and other undesirable constituents. Thus, mildly (insufficiently) refined LOBs are potentially more hazardous than more severely (sufficiently) refined LOBs. This article discusses the evaluation of LOBs using statistical models based on content of PACs; these models indicate that insufficiently refined LOBs (potentially carcinogenic LOBs) can also produce systemic and developmental effects with repeated dermal exposure. Experimental data were also obtained in ten 13-week dermal studies in rats, eight 4-week dermal studies in rabbits, and seven dermal developmental toxicity studies with sufficiently refined LOBs (noncarcinogenic and commonly marketed) in which no observed adverse effect levels for systemic toxicity and developmental toxicity were 1000 to 2000 mg/kg/d with dermal exposures, typically the highest dose tested. Results in both oral and inhalation developmental toxicity studies were similar. This absence of toxicologically relevant findings was consistent with lower PAC content of sufficiently refined LOBs. Based on data on reproductive organs with repeated dosing and parameters in developmental toxicity studies, sufficiently refined LOBs are likely to have little, if any, effect on reproductive parameters.

A consistent and transparent approach for calculation of Derived No-Effect Levels (DNELs) for petroleum substances.

The REACH legislation introduced Derived No-Effect Levels (DNELs) which are defined as 'the levels of exposure above which humans should not be exposed'. DNELs were required for several categories of petroleum substances and CONCAWE developed a consistent approach for their derivation. First, the No-Observed Effect Level from a relevant study was corrected for pattern and route of exposure to obtain a modified Point-of-Departure (POD(modified)). Subsequently, the DNEL was calculated by dividing the POD(modified) by Assessment Factors (AFs) to adjust for inter- and intraspecies differences. If substance-specific information allowed, Informed Assessment Factors (IAFs), developed by CONCAWE were utilised. When little or no substance-specific information on those differences was known, default AFs from the guidance provided by ECHA were used. Some hazard endpoints did not lend themselves to calculation of DNELs (e.g. aspiration, dermal irritation, mutagenicity). DNEL calculation was considered not appropriate if adverse effects were not observed in tests conducted at a limit dose or if meaningful dose-response curves could not be developed. However, DNELs were calculated when hazards were identified, regardless of whether or not risk characterisation was required under REACH. Examples for gasoline, Lubricating Base Oils, gas oils and bitumen are provided to illustrate CONCAWE's approach.

Respiratory toxicology of mineral oils in laboratory animals.

Early subchronic and chronic inhalation toxicology studies on various petroleum mineral oils and formulated lubricants supported the ACGIH TLV of 5 mg/m(3) for mineral oil mist. Additional subchronic studies with aerosolized mineral base oils and lubricants during the last 15 years demonstrated that exposures to aerosols of mineral base oils (often >100 mg/m(3)) resulted mainly in concentration-related accumulation in the lung of alveolar macrophages laden with oil droplets. Inflammatory cells were observed with higher aerosol concentrations, consistent with the clinical literature from highly exposed workers. These pulmonary changes appeared to be a nonspecific response to the presence of deposited aerosol. Studies on sensory irritation during exposures of lab animals to mineral oils indicate possible effects only with very high aerosol concentrations. Coupled with changes in refining to remove carcinogenic polynuclear aromatic hydrocarbons from mineral oils several decades ago, this information indicates that current aerosols of mineral oils have a profile of low toxicity from acute to long-term exposures. Available information suggests that additives in some formulated products and/or maintenance of mineral-based metalworking fluids may play a much more significant role in potential health effects.