A Technical Overview of Crude Tire Oil Price: Specifications and Applications

Types of Crude Tire Oil & Price Ranges

Understanding the different types of crude tire oil is essential for buyers, suppliers, and recyclers in the waste-to-energy and industrial feedstock sectors. The crude tire oil price varies significantly based on several key factors including the production method, refinement level, quality control, and geographical origin. These variations not only affect cost but also determine suitability for specific industrial applications such as fuel blending, chemical synthesis, or lubricant production.

Below is a detailed breakdown of the primary types of crude tire oil available in the market, along with their typical price ranges (per metric ton) and key characteristics:

Scrap Tire Oil (STO)

The most basic form of tire-derived oil, typically obtained through initial pyrolysis of shredded scrap tires without further refinement.

Advantages

• Lowest production cost
• Widely available globally
• Contains recoverable hydrocarbons
• Suitable for preliminary fuel use

Limitations

• High impurity levels (ash, sulfur, solids)
• Inconsistent quality between batches
• Limited to low-grade industrial burners

Price Range: $50 – $200 per ton

Best for: Energy recovery, cement kilns, or as a feedstock for further refining

Reclaimed Oil

Produced through controlled pyrolysis with basic filtration and sedimentation to improve consistency and reduce particulates.

Advantages

• Better clarity and stability than STO
• Reduced sediment content
• More predictable combustion
• Improved safety handling

Limitations

• Higher processing labor and safety costs
• Still contains some contaminants
• Requires storage precautions

Price Range: $100 – $250 per ton

Best for: Industrial boilers, small-scale power generation, and pre-refined feedstock

Expeller Oil

Extracted using mechanical pressing (expeller process), often combined with mild thermal treatment for improved yield and purity.

Advantages

• Cleaner output with stable viscosity
• Lower sulfur and moisture content
• Consistent batch-to-batch quality
• Environmentally safer handling

Limitations

• Moderate yield efficiency
• Higher equipment investment
• Geographically limited production

Price Range: $150 – $300 per ton

Best for: Mid-tier fuel applications, heating systems, and cleaner combustion environments

SOL Oil (Steam Solvent-Extracted)

High-purity oil derived using steam distillation and solvent extraction techniques, resulting in superior clarity and performance.

Advantages

• High thermal efficiency
• Low residue and emissions
• High demand in specialty industries
• Versatile for chemical feedstocks

Limitations

• Energy-intensive production
• Sensitive to market volatility
• Requires advanced refining infrastructure

Price Range: $300 – $600 per ton

Best for: Petrochemical blending, industrial solvents, and high-efficiency fuel systems

Specialty & Purified Tire Oils

Highly refined variants that undergo additional purification, chemical treatment, or custom packaging for targeted applications.

Advantages

• Ultra-low impurities and consistent specs
• Suitable for lubricant base oils
• Potential for low-emission fuel formulations
• High value in niche markets

Limitations

• Very high processing costs
• Limited global supply
• Requires stringent quality certification

Price Range: $600 – $1,200 per ton

Best for: Lubricant manufacturing, premium fuel additives, and chemical synthesis

Expert Tip: When sourcing crude tire oil, always request a certificate of analysis (COA) to verify sulfur content, flash point, viscosity, and water percentage—these factors significantly impact usability and resale value in regulated markets.

As global demand for sustainable energy sources grows, crude tire oil is gaining attention as a viable alternative fuel and chemical resource. However, buyers must carefully evaluate both price and quality to ensure compatibility with their intended application. Investing in higher-grade oils may offer long-term savings through improved efficiency and reduced maintenance costs.

Industrial Applications of Crude Tire Oil

Crude tire oil, derived from the pyrolysis of waste tires, is a versatile byproduct with growing significance in sustainable industrial practices. Despite being a lower-grade fuel, its high calorific value and rich chemical composition make it suitable for a wide range of applications across multiple sectors. Its use not only supports energy recovery but also contributes to circular economy goals by repurposing waste materials into valuable resources.

Key Industrial Applications

Fuel for Energy Generation

With a calorific value comparable to conventional fossil fuels (approximately 40–42 MJ/kg), crude tire oil is widely used as an alternative fuel in high-temperature industrial processes. It is particularly effective in cement kilns, industrial boilers, and thermal power plants where consistent heat is required.

Its combustion produces significant thermal energy, reducing reliance on coal and heavy fuel oil. Many cement manufacturers have adopted crude tire oil due to its ability to sustain high kiln temperatures while lowering operational costs and carbon footprint when managed with proper emission controls.

Manufacturing of Recovered Oils

Through refining processes such as distillation, filtration, and hydrogenation, crude tire oil can be upgraded into higher-value lubricating oils and specialty products. These include industrial lubricants, gear oils, and sealants used in heavy machinery and automotive applications.

Refined tire-derived oils offer competitive performance at lower costs compared to virgin petroleum-based lubricants, making them attractive for industries focused on cost-efficiency and sustainability.

Road Construction Material

Due to its high viscosity and adhesive properties, crude tire oil—especially after partial refining—can be blended into asphalt mixes or converted into modified bitumen and road tars. This enhances the flexibility, durability, and weather resistance of road surfaces.

Tire-oil-modified asphalt reduces cracking, improves skid resistance, and extends pavement life, particularly in regions with extreme temperature fluctuations. It also allows for thinner road layers, reducing material usage and construction costs.

Carbon Black Production

Crude tire oil serves as a critical feedstock in the production of recovered carbon black (rCB), a reinforcing agent used in rubber, plastics, and coatings. Approximately 40% of global carbon black production relies on tire-derived oil, making it the largest industrial consumer of this resource.

rCB enhances tensile strength, UV resistance, and wear performance in tires, hoses, belts, and plastic components. Using tire oil for carbon black reduces the need for virgin fossil-based feedstocks and lowers greenhouse gas emissions.

Chemical Industry Feedstock

Crude tire oil contains a significant concentration of aromatic hydrocarbons such as benzene, toluene, and xylene (BTX), which are foundational chemicals in the petrochemical industry. These compounds are extracted and purified for use in manufacturing plastics, synthetic fibers, resins, dyes, solvents, and pharmaceuticals.

By serving as a secondary source of BTX, tire oil reduces dependency on crude oil refining and supports more sustainable chemical manufacturing pathways.

Agricultural Applications

In certain regions, lower-grade crude tire oil has been explored for use in agricultural formulations, including as a base for herbicides and pesticides. Its hydrophobic nature and phytotoxic properties can inhibit weed growth when applied in controlled conditions.

However, due to potential environmental and soil contamination risks, such applications are limited and highly regulated. Research is ongoing to develop safer, bio-compatible derivatives for sustainable agricultural use.

Production of Energy-Dense Briquettes

Crude tire oil can be combined with shredded tire rubber and other biomass materials to form solid fuel briquettes or pellets. These briquettes have a high energy density and burn efficiently in industrial furnaces and power plants.

This method offers a safe and compact way to utilize both liquid and solid tire waste, minimizing storage challenges and improving combustion efficiency. It’s especially useful in areas lacking access to natural gas or grid electricity.

Feedstock for Further Pyrolysis

Residual crude tire oil can be reprocessed through secondary pyrolysis or catalytic cracking to yield lighter hydrocarbons, syngas, or even synthetic diesel. This enables multi-stage resource recovery, maximizing energy output and minimizing waste.

Advanced processing technologies are increasingly being deployed to upgrade tire oil into drop-in biofuels compatible with existing diesel engines and infrastructure.

Environmental and Economic Considerations

Important: While crude tire oil offers numerous industrial benefits, its use must be carefully managed to avoid environmental contamination and health risks. Combustion should occur in facilities equipped with emission control systems (e.g., scrubbers, filters). Unregulated or improper use—especially in agriculture or open burning—can release harmful pollutants such as PAHs, dioxins, and heavy metals. Always adhere to local environmental regulations and industry best practices.

Product Specifications and Features of Crude Tire Oil

Crude tire oil, derived from the pyrolysis of waste tires, is a versatile hydrocarbon-rich liquid with growing applications in energy, manufacturing, and construction. Understanding its technical properties and proper usage methods is essential for maximizing efficiency, safety, and environmental compliance. This guide provides a comprehensive overview of the key specifications, applications, and handling practices associated with crude tire oil.

Viscosity

Viscosity determines how easily crude tire oil flows and is critical for fuel injection, pumping, and atomization processes. It is typically measured using Saybolt Universal Viscosity (SUV) or Kinematic Viscosity (cSt) at standardized temperatures (e.g., 40°C or 100°C).

• Low-viscosity oils (< 5 cSt) are ideal for direct combustion in burners and engines due to better atomization
• High-viscosity oils (> 10 cSt) may require preheating or blending with lighter fuels for efficient use
• Consistent viscosity ensures stable performance in industrial burners and boilers

Technical Insight: Blending with diesel or biofuels can reduce viscosity for improved combustion efficiency.

Sulfur Content

Sulfur content, measured in parts per million (ppm), significantly impacts environmental compliance and equipment longevity. High sulfur levels contribute to SO₂ emissions and corrosion in engines and exhaust systems.

• Typical sulfur content ranges from 5,000–15,000 ppm, depending on tire source and pyrolysis conditions
• Oils with sulfur > 1% may require desulfurization before use in sensitive applications
• Low-sulfur variants (< 1,000 ppm) are preferred for cleaner combustion and regulatory compliance

Regulatory Note: Many countries limit sulfur in industrial fuels to under 500–3,500 ppm; verify local standards before use.

Aromatic Hydrocarbons

Crude tire oil is rich in aromatic compounds such as benzene, toluene, and xylene (BTX), which enhance its value as a chemical feedstock but pose environmental and health concerns if not properly managed.

• Aromatics can constitute 25–40% of the oil, contributing to high energy density
• These compounds are valuable in petrochemical synthesis but require careful handling due to toxicity
• Long-term exposure risks include respiratory and carcinogenic effects—use proper PPE and ventilation

Safety Tip: Store and process in sealed systems with vapor recovery to minimize emissions.

Boiling Ranges

The boiling profile of crude tire oil defines its distillable fractions and guides refining strategies. Distillation separates the oil into light, middle, and heavy fractions based on boiling points.

• Initial boiling point: ~150°C – indicates presence of light naphtha and solvents
• Final boiling point: ~350°C – marks the end of recoverable fuel-range hydrocarbons
• Key fractions: Naphtha (150–200°C), diesel/gas oil (200–300°C), heavy residue (>300°C)

Refining Advantage: Fractional distillation enables targeted recovery for fuel, lubricant, or chemical production.

Density

Density, measured via hydrometer or pycnometer (typically in g/cm³ or API gravity), influences energy content, storage, and separation efficiency during processing.

• Average density: 0.88–0.95 g/cm³ (slightly heavier than diesel)
• Higher density correlates with greater calorific value but may affect atomization
• Used to calculate volume-to-energy conversion and blending ratios

Practical Use: Density helps determine storage tank capacity and fuel metering settings.

Flash Point

The flash point is the lowest temperature at which the oil emits sufficient vapor to ignite when exposed to a flame. It is a critical safety parameter for storage and handling.

• Typical flash point: 60–85°C, classifying it as a combustible liquid (not flammable)
• Higher flash points reduce fire risk during transport and storage
• Must be stored away from ignition sources and in well-ventilated areas

Safety Standard: Follow OSHA and NFPA guidelines for combustible liquid storage.

Carbon Black Precursor

Due to its high aromatic and carbon content, crude tire oil serves as a valuable feedstock for producing carbon black—a key material in rubber, ink, and pigment industries.

• Residue from distillation can be further processed via thermal cracking to yield high-surface-area carbon black
• Reduces reliance on fossil-based feedstocks and supports circular economy goals
• Yields up to 30–40% carbon-rich residue suitable for upgrading

Sustainability Benefit: Converts waste into a high-value industrial material.

Heat Value (Calorific Energy)

The heat value indicates the energy released during complete combustion, typically measured in kcal/kg or MJ/kg. This determines its effectiveness as a fuel substitute.

• Lower heating value (LHV): ~8,500–9,500 kcal/kg (~35–40 MJ/kg)
• Comparable to heavy fuel oil (HFO) and superior to coal in some cases
• Used in cement kilns, power plants, and industrial boilers as a cost-effective alternative

Economic Advantage: Offers up to 30% cost savings over diesel in high-temperature industrial applications.

Applications and Usage Guidelines

Crude tire oil can be utilized across multiple industries, but proper processing and safety protocols are essential for optimal performance and regulatory compliance.

• Fuel for Energy Generation: Can be directly injected or atomized in industrial furnaces, boilers, and kilns. Preheating (60–80°C) improves flow and combustion efficiency. Best used in dedicated systems with emission controls.
• Lubricant Production: Requires fractional distillation to isolate high-viscosity fractions. Aromatics are removed via solvent extraction, followed by additive blending (e.g., anti-wear, detergents) to meet API standards.
• Road Construction: Used as a bitumen modifier or rejuvenator in asphalt. Mixed with aggregates and conventional binders to enhance flexibility and reduce cracking. Requires minimal processing and improves pavement durability.
• Carbon Black Feedstock: Distillation separates naphtha, gas oil, and aromatic fractions. The heavy residue undergoes controlled pyrolysis to produce industrial-grade carbon black for tires, inks, and coatings.
• Chemical Industry Feedstock: Refined via catalytic cracking or hydrotreating to extract BTX compounds. These serve as raw materials for plastics, solvents, and synthetic fibers.
• Agricultural Uses: Light fractions can be formulated into herbicidal or pesticidal emulsions. However, due to potential toxicity and environmental persistence, this application is limited and regulated in many regions.

Professional Recommendation: Always conduct a full quality analysis (including viscosity, sulfur, flash point, and aromatics) before large-scale use. For fuel applications, consider blending with diesel or biodiesel to improve combustion and reduce emissions. In chemical and lubricant production, invest in proper refining infrastructure to meet industry specifications and ensure product consistency.

Additional Considerations

• Environmental Compliance: Ensure emissions (SO₂, NOₓ, particulates) meet local regulations when used as fuel. Consider scrubbers or catalytic converters.
• Storage Requirements: Store in sealed, corrosion-resistant tanks away from direct sunlight and ignition sources. Use secondary containment to prevent spills.
• Handling Safety: Use PPE (gloves, goggles, respirators) during transfer and processing. Avoid skin contact and inhalation of vapors.
• Quality Variability: Composition varies based on tire type and pyrolysis conditions. Regular testing is essential for consistent performance.
• Regulatory Status: Classified as a secondary fuel or chemical intermediate—verify local classification and permitting requirements.

Quality and Safety Considerations of Crude Tire Oil

Crude tire oil, derived from the pyrolysis of waste tires, presents a promising alternative energy source. However, its quality and safety profile can vary significantly based on processing methods and feedstock. Understanding these factors is essential for safe handling, effective utilization, and compliance with environmental regulations. This guide outlines key quality indicators, safety protocols, and best practices for managing crude tire oil.

Safety Warning: Crude tire oil may contain hazardous substances such as polycyclic aromatic hydrocarbons (PAHs), heavy metals, and sulfur compounds. Always handle with appropriate personal protective equipment (PPE) and in well-ventilated or fume-controlled environments to minimize health risks.

Key Quality Indicators of Crude Tire Oil

• Purity and Contaminant Levels: High-quality crude tire oil should have minimal contamination from metals (e.g., zinc, lead), inorganic residues (ash content), or non-oil organic matter. Impurities reduce combustion efficiency and can damage equipment. Purity can be assessed through laboratory analysis including elemental testing, distillation profiles, and ash content measurement.
• Viscosity: Viscosity affects flow characteristics and suitability for use in engines or burners. Low-quality oil often exhibits abnormally high or inconsistent viscosity due to polymer residues or incomplete cracking. Kinematic viscosity (measured at 40°C and 100°C) is a standard metric—values outside typical ranges (e.g., 3–8 cSt at 40°C) may indicate poor processing or degradation.
• Odor Profile: Freshly processed tire oil typically has a distinct rubber-like aroma. Strong, pungent odors—especially those resembling rotten eggs (hydrogen sulfide) or chemical solvents—may indicate the presence of sulfur compounds, halogens, or unstable hydrocarbons. These require further refining to ensure safe and efficient use.
• Color and Clarity: Color is a preliminary indicator of refinement. Crude tire oil that is dark black or opaque often contains high levels of carbon particles, soot, or unprocessed residues, signaling lower quality. Higher-grade oils tend to be amber, brown, or reddish-brown and relatively clear. Discoloration or sedimentation over time may suggest instability or contamination.

Safety and Handling Best Practices

• Personal Protective Equipment (PPE): Always wear chemical-resistant gloves, safety goggles, and an organic vapor respirator when handling crude tire oil. Skin contact and inhalation of fumes can lead to irritation, respiratory issues, or long-term health effects due to toxic components.
• Safe Storage Protocols: Store crude tire oil in sealed, non-reactive containers made of steel or high-density polyethylene (HDPE). Keep containers in a cool, dry, well-ventilated area away from direct sunlight and ignition sources. Clearly label all containers with contents and hazard warnings. Regularly inspect storage zones for leaks, corrosion, or tampering.
• Spill and Leak Management: Have spill containment kits (absorbents, neutralizers, disposal bags) readily available. In case of a spill, isolate the area, prevent entry into drains or soil, and clean using appropriate absorbent materials. Follow local environmental regulations for disposal of contaminated materials.
• Ventilation and Fire Safety: Use crude tire oil only in areas with adequate ventilation or fume extraction systems. Due to its flammable nature (flash point typically between 60–80°C), keep away from open flames, sparks, and hot surfaces. Maintain fire extinguishers (Class B) nearby.

Waste Management and Environmental Compliance

Residues from crude tire oil—including sludge, filters, and contaminated cleaning materials—are often classified as hazardous waste. Proper disposal is critical to prevent soil and water contamination. Follow these guidelines:

• Never pour waste oil or byproducts down drains or onto the ground.
• Collect all waste in labeled, leak-proof containers designated for hazardous materials.
• Partner with licensed waste management companies for treatment or disposal in accordance with local, state, and federal regulations (e.g., EPA, OSHA).
• Keep detailed records of waste generation, storage, and disposal for audit and compliance purposes.

Expert Tip: Before large-scale use, conduct a small-batch trial of crude tire oil in your intended application (e.g., burner, generator). Monitor performance, emissions, and equipment wear to assess compatibility and refine processing or blending strategies.

Additional Recommendations

• Request a Certificate of Analysis (CoA) from suppliers to verify quality claims.
• Consider upgrading crude oil through filtration, distillation, or hydrotreating to improve quality and safety.
• Educate staff on Material Safety Data Sheets (MSDS/SDS) for crude tire oil used on-site.
• Regularly inspect stored oil for phase separation, sediment, or odor changes that may indicate degradation.
• Explore blending with diesel or other fuels to improve combustion characteristics, if permitted.

Crude tire oil offers economic and environmental benefits when processed and handled responsibly. Prioritizing quality assessment and safety protocols ensures not only operational efficiency but also protects human health and the environment. When in doubt about oil quality or safety, consult a qualified chemist or environmental specialist before proceeding with use or disposal.

Frequently Asked Questions About Crude and Refined Tire Oil

Crude tire oil, derived from the pyrolysis of waste tires, contains impurities and unstable compounds that must be refined before it can be safely and effectively used. The standard refining and processing techniques include:

• Distillation: Separates components based on boiling points, removing lighter fractions and concentrating usable fuel oils.
• Solvent Refining: Uses solvents to extract undesirable compounds such as sulfur, nitrogen, and particulates, improving stability and combustion efficiency.
• Hydroprocessing: Involves reacting the oil with hydrogen under high pressure and temperature to remove impurities and saturate hydrocarbons, enhancing fuel quality.
• Pyrolysis: Though primarily a production method, secondary pyrolysis can further break down heavy residues into more valuable lighter oils.
• Hydrotreating: A specific form of hydroprocessing focused on reducing sulfur, nitrogen, and oxygen content to meet environmental and fuel standards.
• Chemical Additive Blending: Improves performance characteristics such as viscosity, oxidation resistance, and ignition quality for specific applications.

These processes are often combined in stages to produce a cleaner, more stable, and higher-value end product suitable for industrial or energy use.

Assessing the quality of tire-derived oil is crucial for safety, efficiency, and regulatory compliance. Key indicators of high-quality tire oil include:

• Refining/Processing Methods Used: Oils processed through hydrotreating or hydroprocessing generally have lower sulfur and higher stability than those only distilled.
• Purity and Blend: High-quality oil has minimal water, ash, and particulate content, with a consistent hydrocarbon composition.
• Chemical Analysis and Standard Conformity: Lab tests should confirm compliance with international standards (e.g., ISO, ASTM) for flash point, viscosity, sulfur content, and calorific value.
• Color and Odor: Clear, amber-to-light-brown color and a mild petroleum-like odor suggest good refining; dark color or strong foul smell may indicate contamination or incomplete processing.
• Genuine Brands and Certification: Reputable suppliers provide documentation, batch testing reports, and traceability, ensuring transparency and reliability.

Regular third-party testing and adherence to environmental regulations further validate quality and suitability for intended applications.

Once properly refined, tire oil becomes a versatile resource with multiple industrial and commercial applications:

• Fuel: Used as a substitute for diesel or heavy fuel oil in industrial boilers, kilns, and power generators due to its high calorific value.
• Carbon Black Precursor: Can be further processed to recover carbon black, a valuable material used in rubber, plastics, and ink manufacturing.
• Road Construction: Serves as a bitumen modifier or binder in asphalt production, improving flexibility and durability.
• Agricultural Industry: Used in certain farm equipment fuels or as a feedstock for producing agricultural chemicals.
• Chemicals Manufacturing: Acts as a raw material for synthesizing solvents, lubricants, and other petrochemical derivatives.
• Lubricants: After advanced refining, can be formulated into industrial lubricants and greases.

These applications contribute to waste tire recycling and support circular economy initiatives by transforming waste into valuable energy and materials.

Crude tire oil is flammable and may contain hazardous compounds, so proper storage is essential to ensure safety and environmental protection. Best practices include:

• Safe and Sound Containers: Use sealed, corrosion-resistant tanks made of steel or approved plastics, clearly labeled and stored away from ignition sources.
• Housekeeping: Maintain clean, spill-free storage areas with secondary containment (e.g., bunds or drip trays) to prevent soil and water contamination.
• Regular Maintenance Schedules: Inspect tanks, valves, and pipelines routinely for leaks, corrosion, or structural damage.
• Emergency Procedures: Implement spill response plans, fire suppression systems, and employee training for handling accidents or leaks.

Storage facilities should comply with local environmental and occupational safety regulations (e.g., OSHA, EPA) to minimize risks to health, safety, and the environment.

The market price of crude tire oil fluctuates based on several interrelated economic and technical factors:

• Quality: Higher API gravity, lower sulfur, and reduced water content increase value due to better combustion and easier refining.
• Quantity: Bulk purchases often receive discounts, while small batches may carry a premium.
• Market Demand and Supply: Prices rise with increased demand from refineries or energy sectors and drop when supply exceeds demand.
• Geopolitical Issues: Trade restrictions, sanctions, or instability in oil-producing regions can indirectly affect alternative fuel pricing, including tire oil.
• Transportation and Logistics: Proximity to processing plants or ports influences delivery costs and final pricing.
• Regulatory Environment: Stricter environmental standards may increase processing costs, affecting market price.

Understanding these dynamics helps buyers and sellers negotiate fair prices and plan sustainable operations.

The repetition of the quality assessment question (Q2 and Q6) highlights the critical importance of consistent quality evaluation in the tire oil industry. Given the variability in pyrolysis processes and feedstock sources, ensuring product reliability is paramount. Buyers, processors, and regulators must prioritize verification through:

• Batch-specific testing reports
• Third-party certification
• Supplier audits and traceability systems

Establishing standardized quality benchmarks helps build trust in tire-derived oil as a viable alternative fuel and chemical feedstock.

Yes, beyond traditional applications, ongoing research and development are expanding the potential of refined tire oil:

• Biofuel Blending: Mixed with biodiesel or ethanol to create hybrid renewable fuels.
• Marine Fuel: Being tested as a lower-cost alternative to bunker fuel in shipping (subject to emissions regulations).
• Plastic Upcycling: Used as a feedstock in chemical recycling processes to produce new polymers.
• Nanomaterial Production: Advanced processing enables extraction of carbon nanotubes or graphene-like materials from recovered carbon.

These innovations aim to improve sustainability, reduce landfill waste, and unlock higher economic value from end-of-life tires.

Long-term storage of crude tire oil is possible but requires careful management:

• Store in airtight, UV-protected tanks to prevent oxidation and degradation.
• Maintain stable temperatures to avoid phase separation or sludge formation.
• Monitor for microbial growth or water accumulation, which can accelerate corrosion and reduce quality.
• Rotate stock using a "first-in, first-out" system to minimize aging effects.

While crude oil can be stored for several months, it is advisable to process or sell it promptly to maintain quality and reduce storage risks.