Soil, often taken for granted as the inert ground beneath our feet, is a complex and living ecosystem. It’s the foundation of our food supply, a filter for our water, and a home to countless organisms. However, this essential resource can also become a silent threat when contaminated, posing significant risks to human health. Avoiding contaminated soil isn’t just a gardening tip; it’s a critical aspect of public health, environmental stewardship, and personal well-being.
This comprehensive guide delves deep into the multifaceted issue of soil contamination, offering a definitive, actionable roadmap to protect yourself and your loved ones from its hidden dangers. We’ll explore the various sources of contamination, the health risks they present, and, most importantly, provide concrete strategies and practical examples to minimize your exposure.
The Unseen Threat: Understanding Soil Contamination and Its Health Impacts
Before we can effectively avoid contaminated soil, we must first understand what it is, where it comes from, and why it matters to our health. Soil contamination occurs when harmful substances are introduced into the soil at concentrations that are detrimental to human health or the environment. These substances, known as contaminants, can be naturally occurring or, more commonly, introduced through human activities.
Common Contaminants and Their Sources
The array of potential soil contaminants is vast, but some are more prevalent and pose greater health risks than others. Understanding their origins is the first step in prevention.
1. Heavy Metals:
- Lead (Pb): A notorious neurotoxin, lead can accumulate in the body over time, affecting the brain, kidneys, and nervous system, especially in children.
- Sources: Historically, leaded gasoline and lead-based paint were major contributors. Industrial emissions (smelters, battery manufacturing), old orchards (from lead arsenate pesticides), and even some pottery glazes can also be sources. Older homes often have lead paint chips that flake into the surrounding soil.
- Arsenic (As): Both an acute and chronic poison, arsenic is a known human carcinogen linked to skin, bladder, and lung cancers. It can also cause neurological and cardiovascular problems.
- Sources: Naturally occurring in some geological formations. Human-induced sources include historical pesticide use (especially in orchards and cotton fields), mining activities, wood preservatives (chromated copper arsenate – CCA treated wood), and industrial waste.
- Cadmium (Cd): A toxic heavy metal that primarily affects the kidneys, lungs, and bones. Long-term exposure can lead to “itai-itai” disease, characterized by bone pain and fractures.
- Sources: Industrial activities (mining, smelting, battery production), certain fertilizers (superphosphate), and some pigments. It’s also found in cigarette smoke.
- Chromium (Cr): While essential in trace amounts, hexavalent chromium (Cr VI) is highly toxic and a known carcinogen, primarily associated with lung cancer when inhaled.
- Sources: Industrial processes like electroplating, leather tanning, and stainless steel production.
2. Petroleum Hydrocarbons:
- Benzene, Toluene, Ethylbenzene, Xylenes (BTEX): These volatile organic compounds (VOCs) are found in petroleum products. Benzene is a known carcinogen, while others can cause neurological effects, respiratory irritation, and liver/kidney damage.
- Sources: Leaking underground storage tanks (gas stations, old industrial sites), spills from pipelines, improper disposal of motor oil, and industrial solvent use.
- Polycyclic Aromatic Hydrocarbons (PAHs): A group of organic compounds formed during the incomplete combustion of organic matter. Many PAHs are known or suspected carcinogens.
- Sources: Vehicle exhaust, industrial emissions (coal burning, asphalt production), wood smoke, and creosote-treated wood.
3. Pesticides and Herbicides:
- Organochlorine Pesticides (e.g., DDT, Chlordane, Dieldrin): Though many are banned or restricted, their persistence means they can still be found in soil decades later. They are linked to neurological damage, reproductive issues, and certain cancers.
- Sources: Historical agricultural use, termite control around older homes.
- Organophosphates and Carbamates: More acutely toxic, these can affect the nervous system.
- Sources: Current agricultural and residential pest control.
- Herbicides (e.g., Atrazine, Glyphosate): While often considered less toxic than some pesticides, long-term exposure to certain herbicides is being investigated for links to various health issues.
- Sources: Agricultural and residential weed control.
4. Industrial Chemicals:
- Polychlorinated Biphenyls (PCBs): Persistent organic pollutants (POPs) that are highly toxic, affecting the immune, reproductive, nervous, and endocrine systems, and are probable human carcinogens.
- Sources: Old electrical equipment (transformers, capacitors), hydraulic fluids, and some building materials.
- Volatile Organic Compounds (VOCs) – beyond BTEX: Solvents like trichloroethylene (TCE) and perchloroethylene (PCE) are used in dry cleaning and industrial degreasing. They are known to cause liver damage, kidney damage, and neurological effects, and some are carcinogens.
- Sources: Industrial spills, leaking storage tanks, improper disposal of solvents, and contaminated groundwater migrating into soil.
5. Asbestos:
- Asbestos Fibers: Inhalation of asbestos fibers can cause serious lung diseases, including asbestosis, lung cancer, and mesothelioma.
- Sources: Demolition of old buildings containing asbestos (insulation, roofing, floor tiles), mining operations, and manufacturing processes involving asbestos.
Pathways of Exposure: How Contaminants Reach Us
Understanding the contaminants themselves is crucial, but equally important is comprehending the ways they can enter our bodies. There are several primary exposure pathways from contaminated soil:
- Ingestion (Accidental or Intentional): This is perhaps the most common pathway, especially for children. Dirt can be accidentally swallowed during outdoor play, gardening, or eating unwashed produce grown in contaminated soil. Hand-to-mouth contact after touching contaminated soil is a significant route.
- Example: A child playing in a backyard with lead-contaminated soil then putting their hands in their mouth. A gardener eating a tomato directly from the vine without washing it, where soil particles might cling.
- Inhalation (Dust and Vapors): When contaminated soil is dry, dust particles containing contaminants can become airborne and be inhaled. Volatile organic compounds (VOCs) can vaporize from the soil and be inhaled as gases.
- Example: Construction workers excavating a contaminated site inhaling dust. Residents near a landfill inhaling VOCs emanating from the soil. Dry, windy conditions after tilling a garden can create airborne lead-containing dust.
- Dermal Contact (Skin Absorption): While less common for most contaminants, some chemicals can be absorbed through direct skin contact, particularly if there are cuts or abrasions.
- Example: Working barehanded in soil heavily contaminated with certain pesticides or industrial solvents.
- Food Chain Contamination: Contaminants can be taken up by plants grown in contaminated soil, then consumed by humans or animals. Animals that graze on contaminated land can accumulate contaminants in their tissues, which are then consumed by humans.
- Example: Vegetables grown in lead-contaminated garden beds absorbing lead into their edible parts. Livestock grazing on pastures contaminated with arsenic, leading to arsenic accumulation in their meat.
- Water Contamination: Rainwater percolating through contaminated soil can carry contaminants into groundwater or surface water, which may then be used for drinking, irrigation, or recreation.
- Example: A leaky underground storage tank contaminating soil, which then leaches benzene into the local drinking water well.
Vulnerable Populations: Who is Most at Risk?
While anyone can be affected by soil contamination, certain populations are particularly vulnerable due to physiological differences, behavioral patterns, or proximity to contaminated sites.
- Children: More susceptible due to their smaller body size, higher metabolic rates, developing organ systems, and increased hand-to-mouth activity. They absorb certain contaminants more readily and are more likely to play directly in soil.
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Pregnant Women: Exposure to certain contaminants can harm the developing fetus, leading to developmental issues, birth defects, or even miscarriage.
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Elderly: May have compromised immune systems or pre-existing health conditions that make them more vulnerable to the effects of contaminants.
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Workers in Contaminated Environments: Construction workers, agricultural workers, and industrial workers are often exposed to higher concentrations of contaminants through their occupation.
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Residents Near Contaminated Sites: People living adjacent to industrial facilities, landfills, or busy roadways may experience chronic low-level exposure.
Proactive Prevention: Strategies to Avoid Contaminated Soil
Avoiding contaminated soil requires a proactive, multi-layered approach that combines awareness, informed decision-making, and practical protective measures.
1. Know Your Land: Site Assessment and History
The single most crucial step is to understand the history and current condition of the land you inhabit or plan to use. This principle applies whether you’re buying a home, starting a garden, or choosing a park for your children.
- Research Property History (Homebuyers/Renters):
- Check Environmental Records: Inquire with local environmental protection agencies or health departments for records of spills, former industrial uses, or reported contamination on or near the property. Websites like the EPA’s Superfund site list can be helpful, though not exhaustive.
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Investigate Previous Land Use: Was the property historically an industrial site, a gas station, an orchard, or near a major road? Old maps, city directories, and historical aerial photographs can provide clues. Former agricultural land might have pesticide residues; industrial sites could have a range of contaminants.
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Example: Before buying an older home, research if it was built on an old factory site or if it was part of a neighborhood where lead smelting occurred historically. This could indicate potential heavy metal contamination in the soil.
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Soil Testing (Gardening, Construction, Play Areas):
- Professional Soil Analysis: This is the most definitive way to determine if your soil is contaminated. Collect samples from various parts of your property, especially areas designated for gardening or children’s play. Send them to a reputable environmental testing laboratory. Specify what contaminants you are concerned about (e.g., heavy metals, pesticides, petroleum hydrocarbons).
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Interpretation of Results: A professional lab will provide a detailed report with contaminant concentrations and compare them to regulatory screening levels or health-based guidelines. They can advise on whether remediation is necessary or if certain activities are safe.
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Example: If you’re planning a vegetable garden, get a soil test for lead, arsenic, and any pesticides that might have been used historically in your region. If lead levels are above action limits (e.g., 400 ppm for play areas or 100 ppm for vegetable gardens), you know to take mitigating steps.
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Observe Visual Clues: While not a substitute for testing, visual cues can sometimes indicate potential contamination.
- Unusual Odors: Chemical, oily, or pungent smells.
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Stained Soil: Discoloration, oil sheens.
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Lack of Vegetation: Areas where plants struggle to grow or look unhealthy without an obvious reason.
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Unusual Debris: Buried drums, old batteries, industrial waste.
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Example: Noticing an oily sheen on the soil surface near an old shed might indicate a petroleum spill, warranting further investigation.
2. Smart Gardening Practices: Growing Healthy Food Safely
For those who enjoy home gardening, avoiding soil contamination is paramount to ensure the produce you grow is safe to eat.
- Elevated Garden Beds and Raised Containers:
- Barrier Protection: Construct raised beds with a physical barrier (e.g., landscape fabric, heavy-duty plastic liner) at the bottom to prevent plant roots from accessing potentially contaminated native soil.
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Imported Clean Soil: Fill raised beds and containers with certified clean soil, a mixture of compost, and high-quality topsoil from a reputable supplier. Ensure the supplier can provide documentation of the soil’s purity.
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Example: If your urban backyard soil tests high for lead, build raised garden beds 12-18 inches high, line them, and fill them with a 50/50 mix of certified organic compost and new, tested topsoil. This creates a safe growing environment.
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Strategic Plant Selection:
- Root Crops vs. Fruiting/Leafy Crops: Root vegetables (carrots, potatoes) and leafy greens (lettuce, spinach) are more likely to absorb contaminants from the soil than fruiting plants (tomatoes, peppers) or above-ground parts of plants.
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Consider Phytoremediation Potential (Caution!): Some plants are known to hyperaccumulate certain heavy metals. While this can be used for environmental cleanup, these plants should never be consumed if grown in contaminated soil.
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Example: In an area with marginally elevated lead, prioritize growing tomatoes, corn, or beans in ground plots rather than carrots or kale. For root crops or leafy greens, strictly use raised beds with clean soil.
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Thorough Washing of Produce:
- Remove All Soil Residue: Always wash all homegrown fruits and vegetables thoroughly under running water, even if they look clean. Use a vegetable brush for root crops. Peeling root vegetables can further reduce potential contaminant exposure.
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Example: After harvesting carrots from your garden, scrub them vigorously with a stiff brush under cold water, then peel them before cooking.
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Composting Wisely:
- Avoid Contaminated Inputs: Do not compost materials that might introduce contaminants, such as pressure-treated wood scraps, pet waste from animals treated with certain medications, or municipal sludge (unless certified clean).
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Create Your Own Clean Compost: Focus on creating compost from known clean sources like yard waste (leaves, grass clippings from untreated areas), fruit and vegetable scraps, and untreated wood chips.
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Example: Instead of adding sawdust from a demolition site to your compost, use only leaves and grass clippings from your own chemical-free lawn and kitchen vegetable scraps.
3. Protecting Play Areas and Outdoor Spaces
Children are particularly vulnerable to soil contaminants, making their play areas a priority for protection.
- Designated Play Surfaces:
- Use Clean Coverings: Create play areas with surfaces that minimize direct soil contact, such as wood chips, rubber mulch, or sand that has been certified as clean. Ensure these materials are free of contaminants like treated wood (creosote, CCA) or recycled tire rubber (PAHs).
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Example: Instead of letting children play directly on bare soil in an older backyard, install a sandpit with certified clean play sand or lay down a thick layer of untreated wood chips in a designated play zone.
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Maintain Vegetative Cover:
- Reduce Dust and Erosion: A healthy lawn or groundcover helps to bind soil particles, reducing the amount of airborne dust and limiting direct skin contact.
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Example: Ensure bare patches in the yard are reseeded with grass or covered with mulch to prevent soil from becoming airborne dust that children might inhale or ingest.
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Regular Handwashing for Children:
- Post-Play Hygiene: Emphasize and enforce thorough handwashing with soap and water immediately after outdoor play. This is the single most effective way to prevent incidental ingestion of soil particles.
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Example: Keep a bucket of water and soap or hand sanitizer near the backdoor for immediate hand cleaning after children come in from playing outside.
4. Safe Practices During Construction and Renovation
Disturbing soil, especially in older properties or industrial areas, can release dormant contaminants into the air and expose workers and residents.
- Dust Control Measures:
- Wetting Soil: Lightly wet down soil before and during excavation or demolition to minimize airborne dust.
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Containment: Use tarps, plastic sheeting, and temporary barriers to contain dust and prevent it from spreading to other areas.
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Example: When excavating for a new foundation on an older property, continuously mist the exposed soil with water and cover excavated piles with tarps at the end of the day.
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Personal Protective Equipment (PPE):
- Gloves and Respirators: Wear appropriate gloves (e.g., heavy-duty work gloves) to prevent dermal contact and N95 respirators (or higher protection, depending on contaminant) to filter out airborne dust particles.
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Example: If digging in an area suspected of lead contamination, wear robust gloves and an N95 mask, especially if the soil is dry and dusty.
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Proper Soil Disposal:
- Test Before Disposal: Do not dispose of excavated soil without first testing it, especially if contamination is suspected. Contaminated soil must be handled and disposed of by licensed waste management facilities according to local, state, and federal regulations.
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Prevent Spreading: Ensure contaminated soil is not tracked off-site or mixed with clean soil.
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Example: If removing soil from a former industrial site, sample it thoroughly. If lead or petroleum contaminants are detected above regulatory limits, arrange for its disposal at a hazardous waste landfill.
5. Managing Runoff and Water Contamination
Soil contamination can migrate through water, impacting adjacent areas and water sources.
- Erosion Control:
- Vegetation and Landscaping: Use groundcovers, retaining walls, and proper grading to prevent soil erosion, which can transport contaminated soil particles.
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Example: On a sloped property near a former industrial site, plant dense groundcover or install terraces to stabilize the soil and prevent contaminated runoff from entering a nearby stream.
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Stormwater Management:
- Permeable Surfaces: Promote infiltration of rainwater into the ground using permeable pavers or rain gardens to reduce surface runoff that can pick up contaminants.
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Avoid Direct Discharge: Prevent direct discharge of contaminated runoff into storm drains or natural water bodies.
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Example: If you have an area of concern, consider a rain garden that can help filter stormwater runoff before it enters the municipal drainage system, potentially trapping some contaminants.
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Proper Waste Disposal:
- Hazardous Waste Collection: Never pour hazardous chemicals (e.g., old paints, solvents, motor oil) onto the ground or down storm drains. Utilize local hazardous waste collection programs.
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Septic System Maintenance: Regularly maintain septic systems to prevent leaks that can contaminate surrounding soil and groundwater.
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Example: Instead of pouring old paint thinner onto the ground, take it to your local household hazardous waste collection event.
6. Informed Consumer Choices and Advocacy
Beyond individual actions, contributing to broader solutions is vital.
- Support Sustainable Practices:
- Organic Agriculture: Choose organically grown produce when possible, as it minimizes exposure to pesticide residues in food and promotes healthier soil management practices.
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Eco-Friendly Products: Opt for household and garden products that are non-toxic and biodegradable, reducing the chemical burden on the environment.
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Example: When grocery shopping, prioritize certified organic produce, especially for items typically high in pesticide residues.
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Advocate for Stronger Regulations:
- Community Involvement: Participate in local planning and zoning meetings. Support policies that promote brownfield redevelopment, stricter industrial discharge limits, and proper waste management.
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Environmental Groups: Join or support environmental organizations working to identify and remediate contaminated sites and prevent future pollution.
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Example: Attend a public meeting to voice support for funding a local brownfield cleanup project, transforming a contaminated industrial site into a community park.
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Stay Informed:
- Reliable Sources: Follow updates from reputable health and environmental agencies (e.g., WHO, EPA, local health departments) regarding soil contamination issues in your area.
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Community Alerts: Pay attention to local news and community alerts about environmental hazards.
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Example: Regularly check your local health department’s website for any advisories regarding soil or water quality in your neighborhood.
7. Post-Exposure Measures and Health Monitoring
Despite best efforts, exposure can occur. Knowing what to do afterward is crucial.
- Immediate Hygiene:
- Wash Thoroughly: If you suspect contact with contaminated soil, wash all exposed skin with soap and water immediately. Remove and wash contaminated clothing separately.
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Example: After working in a garden where lead contamination is suspected, immediately remove your gardening clothes, put them in the wash, and thoroughly wash your hands and arms.
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Health Monitoring (If Exposure Suspected):
- Consult a Doctor: If you or a family member has had significant exposure to known or suspected contaminated soil, or if symptoms develop, consult a healthcare professional. They can advise on appropriate testing (e.g., blood lead level test) and monitoring.
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Inform Your Doctor: Provide your doctor with as much information as possible about the potential contaminant and exposure scenario.
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Example: If a child has been playing in an area later found to have high lead levels, discuss a blood lead test with your pediatrician, even if no symptoms are apparent.
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Remediation and Mitigation:
- Professional Cleanup: For serious contamination, professional remediation (e.g., soil removal, stabilization, capping) may be necessary. This is a specialized field and should only be undertaken by qualified environmental contractors.
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Containment: In some cases, capping contaminated soil with impermeable barriers (concrete, thick clay, or synthetic liners) can prevent exposure, though this does not remove the contaminants.
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Example: If a soil test reveals dangerously high levels of contaminants across a large area of your property, engage a licensed environmental consulting firm to assess remediation options.
A Healthier Future, Ground Up
Avoiding contaminated soil is an ongoing commitment to personal and public health. It demands vigilance, education, and a willingness to adopt protective measures. By understanding the sources of contamination, recognizing the pathways of exposure, and implementing the actionable strategies outlined in this guide, we can significantly reduce the risks associated with harmful substances in our environment.
From researching property history and testing your garden soil to adopting safe play practices for children and advocating for broader environmental protection, every step contributes to a healthier future. The soil beneath us is a vital resource; protecting it, and ourselves from its potential hazards, is an investment in our well-being and the health of generations to come. By making informed choices and taking decisive action, we cultivate not just gardens, but a healthier, safer world for all.