Ohio VAP Groundwater Standards - Pesticides and PCBs

Overview

These are the Ohio VAP unrestricted potable use standards (UPUS) for pesticides, herbicides, and polychlorinated biphenyls (PCBs) in groundwater from the CIDARS database, effective February 16, 2025.

The UPUS is the lower of the risk-based groundwater concentration and the federal Safe Drinking Water Act MCL. Unlike SVOCs and PAHs, many pesticides have federal MCLs because they are common drinking water contaminants in agricultural areas.

PCBs in Groundwater

PCBs are hydrophobic and strongly adsorb to soil organic matter, so they are not commonly found dissolved in groundwater at high concentrations. When PCBs are detected in groundwater, it usually indicates a nearby source area with very high concentrations or the presence of PCB-containing oils (NAPL) in the subsurface.

The Total PCB UPUS is 0.5 µg/L (the MCL), but individual Aroclor risk-based values are lower - most at 0.079 µg/L. When comparing analytical results, note whether your lab reports individual Aroclors or Total PCBs, as this determines which standard applies.

Aroclor 1016 is an outlier with a UPUS of 1.4 µg/L (non-cancer risk-based) - significantly higher than other Aroclors because it has lower chlorine content and lower toxicity.

Key Pesticide Groups

Organochlorines

These are the most restrictive pesticide standards in groundwater due to their carcinogenicity and persistence:

• Aldrin - UPUS of 0.0092 µg/L (9.2 ppt). No MCL exists; the UPUS is entirely risk-based. This is one of the lowest standards in CIDARS.
• Dieldrin - UPUS of 0.018 µg/L (18 ppt). Aldrin converts to dieldrin in the environment.
• Chlordecone (Kepone) - UPUS of 0.035 µg/L. Historical manufacturing contamination, primarily in Virginia but can be found at pesticide distribution facilities.
• Alpha-HCH - UPUS of 0.072 µg/L. A byproduct of lindane manufacturing.
• DDT - UPUS of 2.3 µg/L. No MCL. Despite being banned since 1972, DDT and its breakdown products (DDE, DDD) persist in soil and can leach to groundwater at heavily contaminated sites.

Compounds with MCLs

These pesticides have federal drinking water standards:

Note that for chlordane, the risk-based value (0.2 µg/L) is lower than the MCL (2 µg/L). The MCL still controls as the UPUS, but this indicates that the health-based risk threshold is more restrictive than the enforceable standard.

Practical Notes

• Agricultural history matters. If a property has historical agricultural use, pesticide sampling should include the full organochlorine suite (aldrin, dieldrin, DDT/DDE/DDD, chlordane, heptachlor, toxaphene, lindane) plus common herbicides (atrazine, 2,4-D, simazine).
• PCB detection limits. Individual Aroclor UPUS values of 0.047-0.079 µg/L require low-level analytical methods. EPA Method 8082 can typically achieve these limits, but confirm with your laboratory.
• Pesticide degradation products should be included in your analytical program. DDT breaks down to DDE and DDD. Aldrin converts to dieldrin. Heptachlor converts to heptachlor epoxide. The breakdown products are often more persistent than the parent compound.
• Atrazine is the most commonly detected pesticide in Ohio groundwater, particularly in agricultural areas of western and northwestern Ohio. Its UPUS of 3 µg/L equals the MCL.
• Glyphosate requires a separate analytical method (EPA Method 547) - it is not included in standard pesticide screens. If glyphosate is a potential contaminant, it must be specifically requested from the lab.