A new report warns that over 62 million Americans, representing roughly one in five people, may be exposed to potentially dangerous levels of nitrates in their tap water. Nitrates, originating from agricultural fertilizers, pose health risks when they leach into groundwater and public water systems.
Understanding Nitrate Contamination
Nitrates are compounds of nitrogen and oxygen naturally found in air, water, soil, and plants. The contamination becomes a health concern when nitrogen-rich fertilizers used in agriculture leach into groundwater, streams, and rivers, eventually entering public water supplies miles downstream.
- Invisible Threat: Nitrates are tasteless and odorless, making them difficult to detect without testing.
- Health Concerns: The Environmental Working Group (EWG) report links low concentrations of nitrates to potential health issues, including:
- Thyroid disease
- Gastric, kidney, bladder, and colon cancers
- Preterm births and birth defects
Current Guidelines vs. Emerging Science
The federal safety guideline for nitrates, established in 1962, sets the limit at 10 milligrams per liter (mg/L). However, the report highlights that numerous peer-reviewed studies suggest potential health associations at much lower levels:
- 5 mg/L
- 3 mg/L
- As low as 2 mg/L
Researchers utilized the EWG tap water database, which aggregates data from nearly 50,000 public water systems across all 50 states, mapping exposure down to 3 mg/L.
Scope of Contamination Findings
According to the EWG report, the contamination levels are widespread and concerning:
- High Exposure: More than 6,000 community water systems, serving over 62.1 million people, tested at or above the 3 mg/L threshold.
- Cancer Links: Over 3,200 of those systems tested at or above 5 mg/L, a level associated with colorectal and ovarian cancer.
- Major Cities Affected: The Los Angeles Department of Water and Power, serving nearly 4 million people, tested above 3 mg/L on 255 separate occasions. Other major cities flagged included Phoenix, Philadelphia, Las Vegas, San Jose, and Columbus.
- Groundwater Risks: The highest contamination levels (e.g., 50 mg/L) were found in groundwater systems, often sourced from local wells, with the primary sources cited being livestock manure and nitrogen-rich fertilizers.
Industry and Expert Responses
- Industry Perspective: A spokesperson for The Fertilizer Institute noted that attributing high nitrate levels solely to fertilizer use oversimplifies the issue, citing other sources like organic matter mineralization, septic systems, and atmospheric nitrogen deposition.
- Expert Commentary: Experts emphasize that contamination can travel far downstream from agricultural areas, affecting both small rural towns and large metropolitan areas.
Recommendations for Consumers
Since current regulations may not align with the latest scientific findings, experts advise consumers to take proactive measures:
- Testing: Consumers can use the EWG's searchable zip code database to check local nitrate levels.
- Filtration: The recommended solution for peace of mind is a reverse osmosis (RO) system installed on the cold-water kitchen tap. This system can capture up to 99% of contaminants.
- Caution: Experts advise against relying solely on bottled water, as its regulation is less comprehensive than tap water standards.
