Methodology
Interested in finding out how much information bottled water companies make available to their consumers, in February 2008 EWG invited the public to send labels from bottled waters that they had purchased. Between February and August 2008 we received 163 unique product labels representing 137 brands from 30 states.
EWG's researchers logged into a database the details of information on the label regarding water source, treatment and testing. We recorded similar data from company websites.
In January 2009, California’s SB 220 went into effect, requiring all bottled waters sold in that state to include on their label the source of the water and contact information for consumers to obtain a report on water quality. Aware that this new rule would prompt changes in the bottled water industry, in May 2009 EWG again invited the public to send us labels of bottled water purchased after the law went into effect. In May and June 2009 we received 85 unique product labels representing 76 brands from 32 states.
We logged the details from this set of labels and corresponding websites into the EWG database and dated the entries appropriately. The final database, a combination of information from products purchased before and after SB220’s effective date, consisted of 188 products from 155 brands and 38 states.
EWG researchers analyzed the information in the database and scored each product based on: 1) the transparency of bottled water company with regards to disclosing source, purification and testing information on both their product label as well as on their website, and 2) the efficacy of purification methods used to treat the water.
The table below details the matrix used to determine the transparency score.
Scoring system — EWG method to rate bottled water
| Label Details | Website Details | |
| Water Source | ||
| Precise source name and location | 2 pts | 1 pt |
| Multiple, specific source names and locations listed as possibilities | 1.5 pts | 0.75 pt |
| Partial or vague1 | 1 pt | 0.5 pts |
| Product name is the only indicator of source | 0.5 pts | 0.2 pts |
| None listed | 0 pts | 0 pts |
| No website | --- | 0 pts |
| Purification | ||
| Treatments named/Lack of treatment disclosed | 2 pts | 1 pt |
| Partial or vague2 | 1 pt | 0.5 pts |
| Product name is the only indicator of purification | 0.5 pts | 0.2 pts |
| None listed | 0 pts | 0 pts |
| No website | --- | 0 pts |
| Testing Conducted | ||
| Statement on label with information about obtaining a water quality report | 1 pt | --- |
| Water Quality Report available | --- | 0.5 pts |
| Report lists full SDWA* contaminant list | --- | 0.5 pts |
| Report lists partial SDWA* contaminant list | --- | 0.2 pts |
| Report includes complete documentation of all chemicals tested for | --- | 0.5 pts |
| Report only includes partial documentation of all chemicals tested for | --- | 0.2 pts |
| Report represents the most current water quality data | --- | 0.5 pts |
| Report is either a "typical" analysis or is undated | --- | 0.2 pts |
2Partial or vague purification information refers to products that do not make clear the treatment processes used, or the lack thereof. An example is the phrase "state of the art ultra-purification system" with no further clarification.
*SDWA- Safe Drinking Water Act: "The Safe Drinking Water Act (SDWA) is the main federal law that ensures the quality of Americans' drinking water. Under SDWA, EPA sets standards for drinking water quality" (EPA, 2009).
We assigned a transparency score to each bottled water product by summing the categorical scores and then factored in purification efficacy by subtracting points where advanced treatment processes, such as reverse osmosis and distillation, were not applied.
Purification Efficacy
| Advanced Treatment Used | 0 pts |
| Basic Treatment Used | -0.5 pts |
| No Treatment Used/None Listed | -1 pt |
We represented the overall score as a letter grade based on the key below, and added a check mark to indicate products purified with advanced processes.
Letter grade key
| A | 8.6 - 10.0 |
| B | 6.9 - 8.5 |
| C | 5.0 - 6.8 |
| D | 2.9 - 4.9 |
| F | 1.0 - 2.8 |
