Coffee capsule contains much more of furan (a potentially carcinogenic substance) that the coffee powder from the traditional coffeemaker, According to a Spanish study. Javier Santos, Department of analytical chemistry at the University of Barcelona, explains that “This is not the same thing to prepare a coffee in a traditional coffee maker, in a coffee maker or espresso capsules, because they lead to different levels of furan”.
What are the different identified levels ?
Furan concentrations :
- Coffee capsule : 117 to 244 ng/ml (nanograms per millilitre, 1 NG = 109 g)
- Espresso : 43 to 146 ng/ml
- Coffee filter coffee : 20 to 78 ng/ml and 14 to 65 ng/ml for decaffeinated coffee
- Instant coffee : 12 to 35 ng/ml
That is what the furan ?
“Furan is a colorless volatile organic compound used in some industries for the manufacture of chemical substances. This substance can also be found in low concentrations in food heat treated such as foods canned or potted. Various mechanisms can be the source of the formation of Furan in food, and it is based on the natural presence of various triggers compounds which are subject to a thermal deterioration or chemical rearrangements during food processing.” 
“In may 2004, the Food and Drug Administration of the United States (FDA) has detected low levels of Furan in a wider variety of foods than had been reported previously, more often in food subjected to a heat treatment such as canning or canning.” 
Of after Health Canada, the main foods containing high levels of furan are : coffee, soups, stews and chilis containing meat, canned pasta dishes. Note that found also at high rates in the jars for babies with meat and vegetables.
Effects of furan on health
“The international agency for research on Cancer (IARC) has classified as furan potentially carcinogenic to humans.” 
The risks to humans are at the moment still poorly known. Studies are underway to better know the effects of small doses of furan we ingest. In 2010, the JECFA (Joint international Committee FAO.WHO expert on food additives) has concluded that furan is worrying for health and that the research, who are current, are a priority.
How is it that there are more Furan in capsules ?
Furan, that is a very volatile compound, remains in capsules which are hermetically closed. The machine uses water under high pressure and which, with the speed of the process entails Furan in the drink.
There is apparently little risk to health
The study estimated that the daily intake of furan, in Barcelona, is 0.03 to 0.38 µg/kg body weight (microgram, 1µg = 106g).
Researchers will want reassuring, should be according to them, drink 20 from cafés of capsules per day so that there is danger to health, reports Futura - sciences.com. Well before arriving at toxic doses of furan, adverse effects of caffeine will be felt.
It should be noted that l’EFSA has assessed the exposure of a European between 0.53 to 0.66 µg/kg body weight per day, While the FDA has assessed him to 0.26µg/kg.
There are two ways to lower the rate of Furan in coffee
The report explains that a long roasting time (20 minutes against 10/15 minutes) and what a less hot water (140° C against 200 / 220 ° C) have the effect of reducing the rate of Furan in coffee.
For all other foods should know that once in the open air (cooking in a pan, recipient open, etc.) furan evaporates in the same way, thereby reducing its content.
More details on furan :
- Report of EFSA's 2004 (published in 2005) on furan (in French) : Report-EFSA-Furan
- Link to the report of EFSA's 2010 : www.EFSA.europa.EU
- Study on the potential carcinogenic and genotoxic substances in food such as furan (in French) : CTF 5107 Furan
Main sources :
- http://www.ScienceDirect.com – “Occurrence of furan in coffee from Spanish market: Contribution of brewing and roasting” – Food Chemestry – Volume 126, Issue 4, 15 June 2011, Pages 1527-1532
-  www.HC-SC.GC.ca
- FOEN (1997) Dioxins and furans, the environment n ° 290 specifications, substances dangerous for the environment (in German)