Cook­ing up toxic air

Kitchens with­out ef­fec­tive ex­hausts can also serve a sig­nif­i­cant amount of air pol­lu­tants

Down to Earth - - CON­TENTS - INDU MATHI S

Cplace ev­ery day in OOK­ING TAKES homes across the world. Whether it is done on tra­di­tional mud stoves or on so­phis­ti­cated burn­ers, gases re­leased dur­ing the process en­dan­ger the health and lives of peo­ple in the house. Ex­perts say it is a mis­con­cep­tion that kitchen ex­haust and ven­ti­la­tion are not a ne­ces­sity.

Harm­ful gases and chem­i­cals are re­leased dur­ing com­bus­tion of both kinds of fuel—solid (wood, coal, kerosene) and gas (nat­u­ral, bio, lpg). The list of pol­lu­tants in­cludes ni­tro­gen diox­ide, car­bon monox­ide, par­tic­u­late mat­ter and formalde­hyde. Ac­cord­ing to a study pub­lished in En­vi­ron­men­tal Health Per­spec­tive in Au­gust 2014, around 3 bil­lion peo­ple in the world face house­hold air pol­lu­tion. Though most of these live in poor coun­tries, the prob­lem is not lim­ited to poor coun­tries. The study es­ti­mated that 500,000 to 600,000 peo­ple with low in­comes in the US are ex­posed to in­door pol­lu­tion be­cause their pri­mary source of heat­ing is solid fuel. As per the World Health Or­ga­ni­za­tion es­ti­mates, 4.3 mil­lion peo­ple across the world die ev­ery year due to ill­nesses at­trib­ut­able to house­hold air pol­lu­tion. In com­par­i­son, out­door air pol­lu­tion kills 3.7 mil­lion a year.

Pol­lu­tion from nat­u­ral gas

A study con­ducted by re­searchers from Lawrence Berke­ley Na­tional Lab­o­ra­tory, Cal­i­for­nia, found that the use of nat­u­ral gas for cook­ing gen­er­ates sub­stan­tial quan­ti­ties of the pol­lu­tants. The re­search showed that the level of pol­lu­tants in homes us­ing nat­u­ral gas burn­ers ex­ceeds safe lim­its set by the US En­vi­ron­men­tal Pro­tec­tion Agency (epa). The study was pub­lished in the jour­nal En­vi­ron­men­tal Health Per­spec­tives on Novem­ber 5,2013.

The prob­lems as­so­ci­ated with gas fu­els

are not new. An­other study, pub­lished in Fe­bru­ary 1996 in Lancet, found that ex­po­sure to burn­ing gas stoves in­creases the risk of res­pi­ra­tory prob­lems such as wheez­ing, short­ness of breath and asthma at­tacks. Harm­ful ef­fects as­so­ci­ated with gas burn­ers were also recog­nised d by the Canada gov­ern­ment which h re­leased a Clean Air Guide in 1993. The guide recog­nised gas wa­ter heaters, fur­naces, un­vented space heaters and cook­ing stoves as ma­jor causes of chem­i­cal con­tam­i­na­tion in homes.The agency rec­om­mended the re­place­ment of gas ap­pli­ances ces with elec­tri­cal ones.

Ad­van­tages of gas fuel

De­spite their draw­backs, gas stoves are still bet­ter than solid fuel stoves, says Kirk R Smith, pro­fes­sor of Global En­vi­ron­men­tal Health at the Univer­sity of Cal­i­for­nia, Berke­ley. Ac­cord­ing to him, us­ing gas may re­sult in a slight over­shoot of US stan­dards for a few minor pol­lu­tants, but it is much bet­ter in com­par­i­son to the ex­ten­sive par­tic­u­late mat­ter pro­duced by solid fuel in In­dia. Smith also says that in some cases, burn­ing of gas has been found to ag­gra­vate res­pi­ra­tory prob­lems in chil­dren, but it is not clear whether the ef­fects are due to the emis­sions from the burn­ing of gas or the food it­self. Gas is a clean fuel, he says.

“Noth­ing is per­fectly with­out risk. For those us­ing solid fu­els, gas would be im­mensely bet­ter,” says Smith, and adds, “only in­duc­tion cook­ing pro­duces no pol­lu­tion at all in the house.”

How­ever, in­duc­tion cook­ing too is not com­pletely harm­less be­cause fumes re­leased from food dur­ing cook­ing can harm health. Fry­ing and grilling of food re­leases acrolein which has been as­so­ci­ated with can­cer in some stud­ies. Acrolein is also present in cooked foods in trace quan­ti­ties.It is formed from car­bo­hy­drates, veg­etable oil, an­i­mal fats and amino acids dur­ing cook­ing of food. A study pub­lished in the Jour­nal of Ex­po­sure Science and En­vi­ron­men­tal Epi­demi­ol­ogy in 2013 shows that ex­po­sure to fumes re­leased from cook­ing oil could lead to dna dam­age and can­cer. But there is no con­clu­sive ev­i­dence to link acrolein with can­cer.

“Fumes re­leased in cook­ing pro­cesses such as sea­son­ing with mus­tard, curry leaves, and chilly, can act as res­pi­ra­tory ir­ri­tants in some in­di­vid­u­als,” says Ra­makr­ishna Goud, ad­di­tional pro­fes­sor at the depart­ment of com­mu­nity health, St John’s Med­i­cal Re­search In­sti­tute in Bengaluru.

Ven­ti­la­tion, the best so­lu­tion

Ac­cord­ing to a study con­ducted by the Lawrence Berke­ley Na­tional Lab­o­ra­tory, the use of ex­haust hoods or elec­tronic kitchen chim­neys can con­sid­er­ably re­duce toxic chem­i­cals re­leased dur­ing cook­ing. Brett C Singer, co-au­thor of the study, says, “Our key find­ing is that even with a clean fuel source of nat­u­ral gas used for cook­ing, it is im­por­tant to ven­ti­late when us­ing in­door com­bus­tion. As homes be­come tighter, which im­proves com­fort and re­duces en­ergy needs for heat­ing and cool­ing, it is even more im­por­tant to pro­vide ven­ti­la­tion when cook­ing and us­ing com­bus­tion sources. Oth­er­wise, in­door air qual­ity prob­lems can oc­cur.”

Singer and his team stud­ied the ef­fi­ca­cy­effi of house­hold cook­ing ex­haust hoods in cap­tur­ing and vent­ing out air pol­lu­tants gen­er­ated by gas burn­ers due to com­bus­tion of fu­els. The cap­ture ef­fi­ciency of the seven de­vices they tested var­ied from less than 15 per cent to more than 98 per cent.The study fo found that all ex­haust hoods do a bet­ter job of cap­tur­ing pol­lu­tants gen­er­ated by the two back-burn­ers of a four burner stove than its front burn­ers. The study was pub­lished in En­vi­ron­men­tal Science and Tech­nol­ogy in 2012. The re­searchers sug­gested that im­prove­ments in de­sign, use of grease traps and bet­ter mo­tors can make kitchen chim­neys more ef­fec­tive.

Singer and his team fol­lowed this re­search with an­other one to as­sess the abil­ity of ex­haust hoods in cap­tur­ing pol­lu­tants gen­er­ated by food items dur­ing cook­ing. The team found that the cap­ture ef­fi­ciency of ex­haust hoods in vent­ing out fumes gen­er­ated by food items kept at the back-burn­ers was not much dif­fer­ent from their ef­fi­ciency in vent­ing out fumes gen­er­ated by gas fuel com­bus­tion from back-burn­ers, cal­cu­lated in the pre­vi­ous study. How­ever, the fig­ures were dif­fer­ent for front burn­ers.The study says that cap­ture ef­fi­cien­cies (CE) for “com­bus­tion pol­lu­tants are not pre­dic­tive of CEs for cook­ing-gen­er­ated par­ti­cles un­der all con­di­tions”.The find­ings were pub­lished on­line in the jour­nal In­door Air on May 24, 2014. Singer stresses, “So­lu­tion to avoid­ing pol­lu­tion from gas burn­ers is to ef­fec­tively ven­ti­late.”

In a re­port pub­lished in Jan­uary 2014 by the Berke­ley Lab, Singer and his team said it was a com­mon mis­con­cep­tion that kitchen ex­haust is not nec­es­sary dur­ing cook­ing.The team sug­gested mea­sures to counter kitchen con­tam­i­nants. These in­clude rais­ing pub­lic aware­ness on the need of kitchen ven­ti­la­tion and set­ting per­for­mance tar­gets to en­sure de­vel­op­ment of high qual­ity prod­ucts.


Harm­ful gases and chem­i­cals are re­leased dur­ing com­bus­tion of both solid and gas fu­els

Fry­ing and grilling of food pro­duces acrolein

from car­bo­hy­drates, veg­etable oil, an­i­mal fats and amino acids. Acrolein has been as­so­ci­ated with can­cer in some


Fumes re­leased dur­ing sea­son­ing with mus­tard, curry leaves, and chilly can act as res­pi­ra­tory

ir­ri­tants Pol­lu­tants re­leased dur­ing cook­ing | Ni­tro­gen diox­ide, car­bon monox­ide, par­tic­u­late mat­ter and formalde­hyde Sources of in­door pol­lu­tion | Cook­ing stoves, gas wa­ter heaters, fur­naces

Comb Com­bus­tion of gas re­leases fumes which cause res­pi­ra­tory prob­lems

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