Arsenic shows up in a surprisingly wide range of everyday things: rice, drinking water, seafood, fruit juice, soil, and even older wooden decks and playsets. Some of these sources carry more risk than others, and the type of arsenic matters. Inorganic arsenic is the form linked to serious health problems, while organic arsenic (found mainly in seafood) is largely nontoxic.
Rice and Rice Products
Rice is one of the most significant dietary sources of inorganic arsenic for most people. Rice plants are unusually efficient at absorbing arsenic from flooded paddy soil, and the element concentrates in the grain. An FDA risk assessment found average inorganic arsenic levels of 92 parts per billion (ppb) in white rice and 154 ppb in brown rice. Brown rice contains more because arsenic accumulates in the outer bran layer, which is stripped away to make white rice.
The type of rice matters too. White basmati averaged just 62 ppb of inorganic arsenic, while brown basmati came in at 133 ppb. Infant rice cereals are a particular concern because babies eat more rice relative to their body weight. The FDA found 104 ppb in dry white-rice infant cereal and 119 ppb in brown-rice infant cereal, and has set an action level of 100 ppb for these products. If you want to reduce exposure, choosing white basmati rice, rinsing rice thoroughly, and cooking it in excess water (then draining) can all help lower arsenic levels in the cooked grain.
Drinking Water
Groundwater is a major route of arsenic exposure worldwide. Arsenic occurs naturally in over 200 minerals, and the most common source mineral is arsenopyrite, an iron-arsenic compound found in many types of rock. When iron and aluminum oxides in underground sediments dissolve under the right chemical conditions, arsenic is released into the water. Bacteria in the sediment accelerate this process. The deeper the sediment layer, the higher the arsenic concentration tends to be.
In the United States, the EPA sets the maximum allowable arsenic level in public drinking water at 10 ppb. That standard took effect in 2001, replacing an older limit of 50 ppb. Private wells are not covered by this regulation, which is why testing is important if your household relies on well water, especially in regions with known arsenic-rich geology like parts of the American Southwest, New England, and the Upper Midwest.
Seafood and Seaweed
Fish and shellfish can contain high total arsenic levels, but nearly all of it is in organic forms that your body doesn’t absorb or metabolize the same way. The dominant compound in most finfish is arsenobetaine, which is nontoxic and passes through the body unchanged. Crustaceans like shrimp and crab are similar. For this reason, the arsenic in a piece of salmon or a serving of shrimp is not considered a health concern comparable to the arsenic in rice or water.
Seaweed is the exception. Marine algae accumulate arsenic from seawater at high concentrations, typically 20 to 100 milligrams per kilogram of dry weight. Most seaweed stores arsenic as organic sugar compounds, but one variety, hijiki (a brown algae), contains mostly inorganic arsenic. Several countries have issued warnings about hijiki consumption for this reason. Bivalves like mussels and clams can also contain elevated inorganic arsenic at certain sites, though this varies by location.
Pressure-Treated Wood
For decades, the most common wood preservative in the U.S. was chromated copper arsenate, or CCA. It protected lumber from insects and rot, and was used extensively for residential decks, playsets, picnic tables, and fences. In 2003, manufacturers voluntarily stopped producing CCA-treated wood for homeowner use, but existing structures were not required to be removed.
If your home has a deck or playset built before 2004, it may contain CCA-treated wood. The EPA recommends applying a penetrating stain or sealant regularly to reduce arsenic leaching from the surface. You should never burn CCA-treated wood, since the smoke and ash release arsenic into the air. CCA is still approved for nonresidential applications like utility poles, marine pilings, and highway structures.
Soil and Agricultural Land
Background arsenic in most soils ranges from 3 to 10 milligrams per kilogram, but levels can be much higher in certain areas. Soils near old orchards are one common hotspot: lead arsenate was widely used as a pesticide on apple and cherry orchards from the late 1800s through the mid-1900s, and it wasn’t officially banned in the U.S. until 1988. That arsenic persists in the topsoil decades later. Areas with high iron oxide content in the soil also tend to have elevated arsenic.
Organic arsenical herbicides were used on cotton fields, golf courses, and sod farms into the 2000s, and some uses continued until 2013. Arsenic is also still used in glass manufacturing and semiconductor production.
How Arsenic Affects the Body
Inorganic arsenic disrupts how your cells produce energy. It enters the mitochondria, the structures inside cells responsible for generating fuel, and shuts down multiple enzymes involved in that process. The result is reduced energy output at the cellular level: lower levels of the molecule cells use as their primary energy currency, a weakened ability to burn nutrients efficiently, and increased “leakage” in the energy production chain. Cells are forced to switch to a less efficient backup energy pathway.
Chronic exposure to inorganic arsenic through drinking water is linked to increased risk of bladder cancer and skin cancer. Cancers of the lung, liver, kidney, and digestive tract have also been associated with long-term exposure. Skin changes, including darkened patches and small hard spots on the palms and soles, are among the earliest visible signs of ongoing arsenic exposure.
How Exposure Is Measured
If arsenic exposure is suspected, a urine test is the most useful measure. Normal total urinary arsenic falls below 50 micrograms per liter for the general population, and levels above 100 micrograms per liter are considered clearly abnormal. Blood testing is less helpful because arsenic clears from the bloodstream quickly. Normal blood arsenic in unexposed people is less than 1 microgram per deciliter. If you eat a lot of seafood, mention that before testing, since the nontoxic organic arsenic from fish can temporarily inflate your total urinary arsenic reading.