MN DINH DNG V AN TON THC PHM
NHNG KIM LOAI NNG CO C TNH CAO
GiNG VIN HNG DN: THS. NGUYN TH THANH LONG
SVTH: H TH NGC UYN DNG TH THY NGN NGUYN NGC THY
KIM LOAI NNG TRONG I SNG HIN NAY Trong nhng nm qua, cng tc v sinh thc phm nc ta ang ng trc nhiu thch thc. Nhiu v ng c cp tnh xy ra trong cc ba n gia nh v tp th lm xn xao d lun v x hi. Tuy nhin, ch l phn ni ca vn ng c thc phm. Phn chm chnh l tnh trng ng c mn tnh do thc n b nhim cc ho cht, cc kim loi nng tch ly, gy hi trong c th m cha ai lng ht c hu qu ca n. Cng ngy ng c thc phm do cc kim loi nng cng c quan tm nhiu hn bi nhng tc hi khn lng ca n i vi sc khe ngi tiu dng v bi s gia tng ca loi nguy c nhim ny trong cuc sng.
KHI NIM
Kim loi nng l nhng kim loi c khi lng ring ln hn 5g/cm3. Mt s kim loi nng c th cn thit cho sinh vt, chng c xem l nguyn t vi lng. Mt s khng cn thit cho s sng, khi i vo c th sinh vt c th khng gy c hi g. Kim loi nng gy c hi vi mi trng v c th con ngi khi hm lng ca chng vt qu tiu chun cho php. Hin ti c nhiu nguyn t kim loi nng c th l ngun gy nhim thc phm, nhng nhng nguyn t hay c nhc n nht l ch, thy ngn, cadimi, asen, km, thic
Lm suy gim chc nng thn kinh
nh hng ca c tnh kim loi nng
Ri lon chc nng h thng min dch S mt cn bng pH v acid Bnh ng mch vnh S suy gim nng lng
Ri lon ni tit v h thng sinh snVic cha tr kh khn v nh hng nhiu n sc khe
1. Asen (As) Asen hay cn gi l thch tn. K hiu As v s nguyn t 33. Khi lng nguyn t ca n bng 74,92. Asen ln u tin c Albertus Magnus (c) vit v n vo nm 1250. Asen c nhiu dng th hnh: mu vng (phn t phi kim) v mt vi dng mu en v xm ( kim) .Ba dng c tnh kim loi ca asen vi cu trc tinh th khc nhau cng c tm thy trong t nhin nhng ni chung hay tn ti di dng cc hp cht asenua v asenat. Asen v cc hp cht ca n c s dng lm thuc tr dch hi, thuc tr c, thuc tr su v trong mt lot cc hp kim.
Asen v tnh cht ha hc rt ging vi nguyn t ng trn n trong bng tun hon ha hc l photpho. S tng t ln n mc asen s thay th phn no cho phtpho trong cc phn ng ha sinh hc v v th n gy ra ng c. Tuy nhin, cc liu thp hn mc gy ng c th cc hp cht asen ha tan li ng vai tr ca cc cht kch thch v tng ph bin vi cc liu nh nh l cc loi thuc cha bnh cho con ngi vo gia th k 18.
Trong thi k ng, asen thng c a vo trong ng thic lm cho hp kim tr thnh cng hn (gi l "ng thic asen"). Anh, trong thi i Victoria, 'asen' ('asen trng' khng mu, kt tinh, ha tan) c trn ln vi dm v phn v ph n n n ci thin nc da mt ca h, lm cho da mt ca h tr thnh nht mu hn th hin h khng lm vic ngoi ng. Asen cng c c xt vo mt v tay ph n 'ci thin nc da'. Vic s dng ngu nhin asen trong lm gi thc phm dn ti ng c ko Bradford nm 1858, gy ra ci cht ca khong 20 ngi v lm khong 200 ngi khc b bnh do ng c asen.
Ngun nhim Asen Thc n, nc ung, kh th c cha arsenic. Mt s thuc dc tho (n /Pakistan) c cha Asen Khai thc nc ngm c cha Asen.
Cng nhn lm vic trong nh my, c khng kh nhim bi As, lu ngy tch ly trong c th. Ht khi khi t chy g c tm ha cht c cha arsen bo v chng mi mt. Sng gn khu vc c thi khi nhim arsen. Sng khu vc c ni nhim arsen cao.
c tnh ca Asen: Asen v nhiu hp cht ca n l nhng cht cc k c . Asen ph v vic sn xut ATP thng qua mt s c ch. chu trnh axt citric, asen c ch pyruvat dehydrogenaza v bng cch cnh tranh vi phtphat n tho b phtphorylat ha xi ha, v th c ch qu trnh kh NAD+ c lin quan ti nng lng, h hp ca ti th v tng hp ATP. Sn sinh ca perxt hir cng tng ln, iu ny c th to thnh cc dng xy hot ha v sc cng xi ha. Cc can thip trao i cht ny dn ti ci cht t hi chng ri lon chc nng a c quan.
- Asen c th gy ra 19 cn bnh khc nhau. Cc nh hng chnh i vi sc kho con ngi: lm keo t protein do to phc vi asen III v ph hu qu trnh photpho ho; gy ung th tiu m da, phi, ph qun, xoang - Tiu chun nc ung quy nh asen nh hn 0,01 mg/l.
2. Ch (Pb) Ch c k hiu l Pb v c s nguyn t l 82. Ch l mt kim loi mm, nng, c hi v c th to hnh. Ch c mu trng xanh khi mi ct nhng bt u xn mu thnh xm kh tip xc vi khng kh. Ch dng trong xy dng, c quy ch, n, v l mt phn ca nhiu hp kim. Ch c s nguyn t cao nht trong cc nguyn t bn.
c tnh ca ch Ch l nguyn t c c tnh cao i vi sc kho con ngi. Ch gy c cho h thn kinh trung ng, h thn kinh ngoi bin, tc ng ln h enzim c nhm hot ng cha hyro. Ngi b nhim c ch s b ri lon b phn to huyt (tu xng). Tu theo mc nhim c c th b au bng, au khp, vim thn, cao huyt p, tai bin no, nhim c nng c th gy t vong. c tnh ni bt l sau khi xm nhp vo c th, ch t b o thi m tch t theo thi gian ri mi gy c. - Ch i vo c th con ngi qua nc ung, khng kh v thc n b nhim ch. - Ch tch t xng, km hm qu trnh chuyn ho canxi bng cch km hm s chuyn ho vitamin D. - Tiu chun nc ung v nc sch u quy nh hm lng ch nh hn 0,01 mg/l.
2. Thu ngn (Hg): Khi vo c th, thy ngn s lin kt vi nhm sulfhydryl lm thay i hot ng ca nhm -SH trong cu trc phn t ca cc enzyme. Thy ngn ng li trong cc ng thn. Xut hin protein trong nc tiu. Khi vo c th thy ngn bin i thnh dng methyl thy ngn i khp ni trong c th v n ha tan c trong lipid nn c kh nng tch t li trong c th lu hn. Alkylmercurial c chui carbon ngn thng hp thu vo c th nhiu hn v cng gy c cho c th nhiu hn. Metyl thy ngn rt d hp thu v ln no gy bnh tm thn. Hg nh hng rt r rt n thai nhi, gy d tt bo thai, ri lon sinh l, gy nhng tai bin khng cha tr c. Khi ngi m nhim c th a con sinh ra c th l qui thai.
Thu ngn d bay hi nhit thng nn nu ht phi s rt c. Thu ngn c kh nng phn ng vi axit amin cha lu hunh, cc hemoglobin, abumin; c kh nng lin kt mng t bo, lm thay i hm lng kali, thay i cn bng axit baz ca cc m, lm thiu ht nng lng cung cp cho t bo thn kinh. Tr em b ng c thu ngn s b phn lit, co git khng ch ng. Trong nc, metyl thy ngn l dng c nht, n lm phn lit nhim sc th v ngn cn qu trnh phn chia t bo. - Tiu chun nc ung v nc sch u quy nh hm lng thy ngn phi nh hn 0,001 mg/l.
Ngi ph n Nht vi a con ca mnh l nn nhn ca bnh "Minamata Disease", do nhim c thy ngn Minamata, Nht bn, nm 1973. a con gi d hnh trong vng tay ca m, cng nh nhiu b m khc mc phi chng bnh ny c lin quan n nn cng nghip phn bn, ha du m v cng nghip cht do... xung vnh Minamata khang 27 tn thy ngn t nm 1932 n 1968 Nht Bn lm cho trn 10,000 dn chu nh hng do n hi sn ni ny.
4. Cadimi (Cd) L nguyn t kim loi tng i mi vi con ngi Ngun nhim: S bo mn t nhin c cha Cadmium L nu ng, ch v km lm bay ra cadmium Ht thuc l (mi iu thuc cha 1-2 g Cd) Nhng ng dng Cadmium: M kim loi Lm pin sc Nickel-Cadmium. Hp kim hn Lm mu sn (xanh nc bin) Cht n nh cht do. Ha cht trong k thut nhip nh Lm thuc dit nm D dng hp thu v tch ly trong thc vt.
C ch tc ng: Gn vo nhm SH Cnh tranh vi Zn v Se cho tt c cc metalloenzyme Cnh tranh vi calcium v tr gn (calmodulin) c tnh i vi thn: Cd t do gn vo tiu cu thn Lm mt chc nng ca ng ln gn trong thn. c hi phi: Vim ph v kh thng phi bi cadmium git cht i bch cu phi
nh hng ln b xng: Gy long xng v nhuyn xng (pseudofractures) Gy ung th: Gy ung th trn ng vt th nghim ~8% ca ung th phi c th qui cho l do Cdmium Tiu chun nc ung quy nh Cadimi nh hn 0,003 mg/l.
Itai-itai victim
5.Km (Zn)Km l thnh phn t nhin ca thc n v cn thit cho i sng con ngi. Mt khu phn mu cung cp hng ngy t 0,17 n 0,25 mg Zn/kg th trng. Ni chung, tt c cc loi ng vt u chu ng c km, kim loi m t gy c nu hm lng thp v khu phn n cha nhiu ng, st v chu tc ng tng h gia cc yu t khc. Do c gii hn bo m chc chn gia nng km c trong khu phn n bnh thng hng ngy, vi liu lng km c th gy ng c do tch lu, cho nn vi hm lng km c quy nh gii hn trong thc n (t 5 n 10 ppm) khng nh hng n sc khe ngi tiu dng. Ng c do km cng l ng c do cp tnh, do n nhm phi mt lng ln km (5-10g ZNSO4 hoc 3-5ZnCl2) c th gy cht ngi vi triu chng nh c v kim loi kh chu v dai dng trong ming, nn, tiu chy, m hi lnh, mch p kh, cht sau 10 n 48 giy.
Quyt nh s 867/1998 BYT ngy 4/4/1998
