Results from NH APPLETREE soilSHOP events empower communities

In April and May, the NHDES APPLETREE program offered community members the opportunity to have soil from their gardens or outdoor play areas screened for lead during soilSHOP events in Concord and Nashua. The opportunity was also extended to community gardens across the state. A total of 136 soil samples were collected and screened between the various events and six community gardens. EPA Region 1 supported the events as a partner by providing environmental justice specialists in person and soil sample screening after events. As a bonus, soil screening for arsenic was provided in addition to lead. 

Lead and arsenic soil screening results were sorted into three risk categories depending on the contaminant concentration in parts per million (ppm) by weight (milligrams arsenic/lead per kilogram soil). Risk categories are color coded for easy interpretation and align with federal and state guidance. Concentrations of each contaminant were classified as low risk, potential risk or high risk in order to be protective of human health. See the tables in the Concord and Nashua soilSHOP event results documents for more details. 

Lead is a metal that can naturally be found in the environment but exists at higher levels due to human activity. Past use of lead paint and leaded gasoline are major sources of lead in urban settings. As plants only absorb small amounts of lead, most of the risk comes from ingesting or inhaling soil particles, eating unwashed or unpeeled vegetables grown in the soil or handling contaminated soil. Some plants, such as herbs, root vegetables and leafy greens, tend to accumulate more lead than others. Out of the 136 soil samples screened for lead, the vast majority fell into the low-risk category in our results guidance. Six samples screened in the potential risk category and three screened in the high-risk category. 

Arsenic is a naturally occurring metal-like element that can be found in the soil from both natural and human-related sources. In general, arsenic levels in New Hampshire soils typically run about 12 ppm or less (SHA, 1998). Although garden-related arsenic exposure is generally a minor source of a person’s total arsenic exposure, it is still good practice to reduce or limit your exposure if elevated levels of arsenic are present in the soil, especially for children. As most edible plants only absorb small amounts of arsenic, the majority of the risk would be from ingesting or inhaling soil particles, eating unwashed or unpeeled vegetables grown in the soil, handling soil or touching chromated copper arsenate (CCA) treated wood that may be used for raised beds. Therefore, washing and peeling fruits and vegetables can help reduce or eliminate that exposure. Out of the 136 soil samples screened for arsenic, 52 samples screened in the potential risk category and 29 screened in the high-risk category. 

Anonymous results are posted on the NHDES APPLETREE webpage. Results for community gardens have also been provided directly to community garden coordinators. Environmental health education accompanies these results and gives specific recommendations to reduce exposure. For example, children can be particularly vulnerable to ingestion and inhalation of lead and arsenic due to outdoor play on exposed soils and hand-to-mouth activities. To reduce children’s exposure to possible soil contaminants, we recommend preventing children from playing in or on contaminated soil, cleaning toys regularly and having children wash their hands and faces after they play in the yard. If possible, cover bare soil with grass or other material such as mulch. 

For soil that screened in the high-risk category for lead and/or arsenic, we recommend considering installing raised garden beds and filling them with clean topsoil and compost from contaminant-free sources. Although no longer available for residential use, older pressure treated wood may contain CCA, a group of pesticides commonly used up until the early 2000s, that contains chromium, copper and arsenic. Therefore, do not use CCA treated wood for a raised bed or in other areas of your yard or garden as the arsenic can leach from the treated wood onto the surface and into the surrounding soil. See additional tips and recommendations below to reduce your exposure to soil contaminants in the yard or garden. 

To reduce possible ingestion of soil contaminants from fruits and vegetables: 

• Clean your hands, cutting boards and kitchen tools with hot, soapy water and rinse well before and after handling your fruits and vegetables. 
• Soak garden produce in cool water and rinse thoroughly until the water runs clear. Commercial vegetable cleaning products are available in supermarkets to help free soil residues from your produce. These products work well with leafy vegetables. Vinegar can also be used for cleaning produce. 
• Scrub firm fruits and root crops with a vegetable-cleaning brush to remove dust and dirt before peeling or eating. 
• Peel root crops like beets, potatoes, carrots, rutabagas, radishes and turnips. 
• Wash berry fruits like raspberries, strawberries and blackberries and remove the “caps” (the tops of the berries where the stem and leaves attach). 

To reduce soil contaminant availability and uptake by plants: 

• Increase the organic matter in your soil by adding compost or manure from outside sources such as commercial garden centers. 
• Keep your soil at a near-neutral pH range (6-7). 
• Maintain adequate levels of plant nutrients by using a balanced commercial fertilizer. 

To reduce exposure to possible contaminants while working in the yard or garden:  

• Avoid eating or drinking while working in the yard or garden because contaminated soil and dust might get on your food, and you could accidentally swallow it. 
• Dampen soils with water before you garden to limit the amount of dust you inhale. 
• Avoid working in the yard on windy days, when dust can be stirred up and possibly increase your exposure. 
• Consider wearing a mask if you spend time in dusty areas. 
• Wear gloves and wash your hands after gardening. 
• Wash your work clothes to remove dust and dirt. 
• Take your shoes off at the door to avoid tracking soil into your home. 

Because soilSHOP screening results have limitations on interpretation, we have conducted follow up with concerned individuals and community gardens. For example, certain gardens were interested in resampling to confirm and better understand the relative distribution of lead and arsenic levels in amended soil and native soil at their locations. Thankfully, the established partnerships we have created through the soilSHOP process are enabling APPLETREE to continue to pursue this outreach. 

Are you interested in having the NHDES APPLETREE program host a soilSHOP event in your community? Contact Robert Thistle at Robert.Thistle@des.nh.gov to start planning today. 

References: 

Sanborn, Head & Associates, Inc. (SHA). (1998). Background Metals Concentration Study - New Hampshire Soils.