Drinking Water Quality

The US Environmental Protection Agency (USEPA) sets regulations for public drinking water systems. The EPA has National Primary Drinking Water Regulations (NPDWRs) and National Secondary Drinking Water Regulations (NSDWRs). Primary standards apply to public water systems and are legally enforceable limits of levels of contaminants in water that protect the health of the public. States have varying authority to enforce secondary standards for non-health related issues, like taste, color, and smell.


The Louisiana Department of Health’s (LDH’s) Safe Drinking Water Program (SDWP) enforces the drinking water regulations for the state and provides several ways to search water quality and regulatory information. For example, consumers can get information about boil water advisories, learn about regulations for lead in school drinking water, and read compliance reports at the SDWP Website: ldh.la.gov/safedrinkingwater. Compliance reports, called Consumer Confidence Reports (CCRs), are published yearly and provide summaries of drinking water data and violation history for each water system. CCRs are required to be distributed by the water systems to all customers.


Tracking Drinking Water Quality in Louisiana

The LDH Tracking network currently tracks the population served by these systems along with nine drinking water contaminants which are monitored in public drinking water. Each of the contaminants listed below is provided with a link to the Toxicological Profile or ‘ToxFAQs’ from the US Agency for Toxic Substances Disease Registry (US ATSDR) Toxic Substances Portal. In addition to general and background information, updated information is also included on how these contaminants may be linked to health effects. More information on each drinking water contaminant can additionally be found through resources at the USEPA listed at the bottom of this page.


Arsenic | Mean Arsenic Concentrations annually, by water system (Ug/L)

Arsenic (As) is a heavy metal that is very poisonous to the human body. Similar to other heavy metals such as Lead (Pb), Arsenic is a systemic poison that could affect many of the processes within the human body. Some studies have indicated exposure to arsenic in the womb to be associated with lower birth weights in children and an increased risk of infant mortality. Arsenic in drinking water is associated with an increased risk of bladder cancer and skin cancer among other serious health effects. Arsenic in drinking water could be naturally occurring due to mineral deposits but could also be introduced into the water supply through the industrial discharge and agricultural run-off.

Atrazine | Mean Atrazine Concentrations annually, by water system (Ug/L)

Atrazine is a widely-applied herbicide which may be applied in crop-production, golf courses and lawns to control certain weeds. It is banned in Europe but not in the US. Atrazine is toxic to coral reefs and endangered species, and poses a chronic risk to fish, amphibians, and aquatic invertebrates. In humans, the herbicide has been implicated in endocrine disruption (chemically, it interferes with hormone regulation, and is linked with developmental, reproductive, brain, and immune interference) and has also been linked to cancers of the breast.


Di(2-ethylhexyl)phthalate (DEHP) | Mean DEHP Concentrations annually, by water system (Ug/L)

DEHP, commonly referred to as phthalate (https://www.atsdr.cdc.gov/ToxProfiles/tp9-c1-b.pdf) is a chemical commonly added to plastics. DEHP can enter the environment through releases from factories or leached from household items such as in landfills. Humans can be exposed to DEHP through air, water, or skin contact with plastics that contain DEHP. No studies have evaluated the potential for DEHP to cause cancer in humans, however based on animal studies the USEPA has determined that DEHP is a probable human carcinogen.


Disinfection by-products (TTHM and HAA5) | Mean TTHM Concentrations annually, by water system (Ug/L) | Mean HAA5 Concentrations annually, by water system (Ug/L)

Disinfection by-products such as TTHM (Total trihalomethanes) and HAA5 (HAA5 is a group of five haloacetic acids: dibromoacetic acid, dichloroacetic acid, monobromoacetic acid, monochloroacetic acid, and trichloroacetic acid) form when gaseous chlorine (Cl2) or another disinfectant used to kill bacteria present in water supplies breaks down along the distribution system. These by-products are currently used as indicator chemicals for all potentially harmful compounds formed by the addition of chlorine to water. Human exposures can occur through the skin, inhaling and drinking. While chlorination is necessary to prevent infectious diseases caused by pathogenic bacteria in drinking-water, the levels of these by-products must be monitored to ensure minimal human exposure. Some by-products have been classified as possible human carcinogens.


Nitrate/Nitrite | Mean PCE Concentrations annually, by water system (Mg/ML)

Nitrate/Nitrite are nutrients which are often used as fertilizer for plants. Nitrate in various forms is used in crop production as plant food. If farmers and agricultural operations do not adequately control the run-off of fertilizers into the water supply, nitrate/nitrite can become pollutants reaching levels that are harmful to aquatic, animal and human health and life. This process of ‘eutrophication’ occurs when fertilizer run off including nitrates may cause ‘algal blooms’ and excessive plant growth which deplete the oxygen (O2) content of waterbodies. As the different types of algae and plants feed on the ‘plant food,’ they also pull O2 from the water which other organisms such as fish require to breathe. The algae and plants replace the O2 with high amounts carbon dioxide (CO2) which can result in fish kills or other harmful impacts to aquatic organisms. Nitrate/nitrites in drinking water at certain levels are a serious harm to pregnant women and babies. Infant methemoglobinemia (not enough oxygen in the blood) can result. This condition is also called “blue baby syndrome” causing the baby's skin to turn blue.


Tetrachloroethene (tetrachloroethylene or PERC) | Mean PCE Concentrations annually, by water system (Ug/L)

Trichloroethene (trichloroethylene or TCE) | Mean TCE Concentrations annually, by water system (Ug/L)

PERC and TCE are chemical solvents. PERC is used as a dry-cleaning agent as well as a solvent. TCE is used to make other chemicals such as refrigerants. Although workers in the chemical industry are more at risk from direct exposures to chemicals such as PERC and TCE, in drinking water some studies in humans suggest that exposure to PERC might lead to an increased risk of bladder cancer, multiple myeloma, or non-Hodgkin’s lymphoma. Health effects from exposure to high levels of TCE can cause cardiac arrhythmias, liver damage, and evidence of kidney damage. According to ATSDR, skin contact with concentrated solutions of TCE can cause skin rashes. ATSDR cites “strong evidence” that TCE can cause kidney cancer in people and some evidence for liver cancer and malignant lymphoma related to TCE exposure.


Uranium | Mean Uranium Concentrations annually, by water system Ug/L

Uranium is a radioactive element. Uranium decays over long periods of time into isotopes such as radium, radon and eventually lead, all of which are toxic to the human body. Uranium occurs naturally in low concentrations in soil, rock and water, but may also be present in the environment as a result of commercial mining or oil and gas activities. Mining and drilling activities can generate waste materials that contain radioactivity and these may enter the drinking water supply through run-off, leaching of waste pits, accidents or careless techniques/operations. According to the USEPA, ionizing radiation can affect the atoms in living cells and damage their genetic material (DNA). Radioactivity is harmful to human health and even in low amounts is a contributor to overall cancer risk. Fortunately, the cells in our bodies are efficient at repairing some of this damage. Uranium may pose a health risk when drinking water is used for drinking and cooking over many years.

Note that for Louisiana public drinking water, only ‘finished’ (treated) water sampling is included in the current dataset, representing a very small subset of the total data that exists. ‘Raw’ water samples (directly from underground or above ground sources) are excluded from the dataset. Systems may be sampled every three years depending on the contaminant, but sampling may move to quarterly monitoring if the running annual average exceeds the standard. Specific to Louisiana, non-detect samples were reported as a zero (0) (CFR 141).

The concentration of each drinking water contaminant during distribution is dependent mainly on the concentration in the water going into the supply, but may be affected by reactions within the distribution system with PH, temperature, water age, organic concentration and/or other variables. Comparisons should not be made between Louisiana parishes because multiple water systems can serve the same parish and multiple parishes can be served by the same water system. More detailed information can be found in the metadata and InfoTab.


Data Sources

Data are derived from the Louisiana Department of Health's Safe Drinking Water Information System (SDWIS), Louisiana Department of Health (LDH) Safe Drinking Water Program

Additional Info

Louisiana Department of Health Safe Drinking Water Program

US Environmental Protection Agency Water Topics

US Centers for Disease Control and Prevention, Healthy Water

US Agency for Toxic Substances Disease Registry

US Geological Survey Science Topics page of the USGS Water Science School