Lead dose spread out? Not really... 鉛劑量攤開？不是真的..

我們怎樣才會鉛中毒？

鉛中毒（鉛中毒）可以從不同的鉛來源;有機或無機的。

有機鉛是鉛含有“碳”和在汽油裡面發現的，它可以通過皮膚被吸收 (但非常少數會從這途徑中毒）。

無機鉛被定義為氧化鉛，金屬鉛和鉛的鹽，

它可以在焊接和水管中找到，大部分鉛中毒多數從這途徑發生，因為無機鉛水溶性

非常高，中毒劑量能低於0.5克。

接觸途徑？

可以經由呼吸道吸入無機鉛（〜40％），或者通過胃腸道吸收（〜10-15％），

但這途徑會令慢性中毒特別顯著如果患者生活或者工作環境受鉛污染。

一旦鉛分發到血液，它會被軟組織和骨骼吸收。鉛在血液通過腎臟排泄和​​清除較快，如果腎功能正常，

鉛具有約30天的平均半衰期。然而，排鉛速度可因患者有慢性鉛暴露和大骨頭鉛存量而變得緩慢。

對比起成年人（3%-10%）兒童身體吸收已攝入的鉛（50-80％）高出5-8倍，因此兒童中毒的風險更大。

毒性也是由鐵和鈣缺乏增強。

接受血清血水平

（健康成人）

<10mcg /dl（0.48micromol/L）（美國標準BLL）

< 20mcg/dL (0.1 micromol/L) (英國標準)

（懷孕和嬰兒）

<5mcg/dL（美國標準BLL）

有什麼體徵和症狀....

急性中毒（> 80mcg / dL的血鉛水平）

●腹痛（“鉛絞痛”）

●便秘

●關節痛

●肌肉酸痛

●頭痛

●厭食

●性慾減退

●難以集中注意力和短期記憶障礙

●易怒

●疲勞過度

●睡眠障礙

●混亂，癲癇，腦病可見有極高濃度的鉛

●貧血

●腎病（範可尼型綜合徵）

慢性暴露（30至70mcg / dL）的

可以無病徵

 或者

肌痛

疲勞

易怒

失眠

厭食

受損的短期記憶

注意力不集中

更嚴重的健康問題.....

高血壓                      （骨鉛，累積鉛暴露的反映，估計是發展中國家高血壓的標準老齡化研究的一個獨立危險因素）

死亡率和心血管效應（長期接觸具有低鉛含量為20〜29mcg /dL（0.97至1.40 micromol/L），

                                   和甚至小於10mcg/dL（0.48micromol/L）在一個報告中，增加死亡率已指出和血含鉛有關）

神經精神效應            (腦病變多數發生在兒童身上, 血含鉛高的兒童可無症狀，但有機會有智力障礙和行為障礙。）

生殖效應  (A)              （男子40和70微克/分升（1.93之間慢性鉛暴露[和血鉛水平3.38micromol / L）已經在一些研究中發現有精子形態異常的百分之增加，

                                  降低精子的濃度，總精子數量和總活動精子數）

生殖效應  (B)                (鉛容易穿過胎盤。發現孕婦出現流產，死胎數量增加，和早產都有相當高的鉛暴露。

                                     根據醫學報導，血，靜脈血液，臍帶血和骨含鉛較高母親所生的嬰兒多有降低出生體重和認知障礙）

How can we get lead poisoning? 

Lead poisoning (plumbism) can be from different source of lead; organic or inorganic.

Organic lead is lead that contained 'carbon' and is usually found in gasoline and it can be absorbed through the skin (which rarely causes any poisoning or toxicity). Inorganic lead is defined as lead oxides, metallic lead and lead salts, which can be found in soldering and  water pipes. Poisoning or toxicities are usually caused by ingestion inorganic lead as it is highly water soluble, toxic dose can be as low as 0.5grams. 

Route of exposure?

Inorganic lead via inhalation (~40%), and via gastrointestinal absorption (~10-15%) BUT it can be a significant contributor, particularly when working and/or eating in a lead-contaminated environment. 

Once absorbed, lead is then distributed to the blood, soft tissues, and skeleton. Lead in blood is excreted via the kidneys and cleared comparatively fast, with a mean half-life of about 30 days if renal function is normal. However, blood clearance can be slower in people with a long history of lead exposure and large bone stores. Children absorb considerably more ingested lead (quoted ranges 50-80%) than adults (3-10%) and are thus at greater risk of developing toxicity. Toxicity is also enhanced by iron and calcium deficiency.

Acceptable serum blood level

(Healthy Adults) <10mcg/dL (0.48 micromol/L) (US BLL standard, readjusted to lower threshold in view of adverse effect in low exposure)

< 20mcg/dL (0.1 micromol/L) (UK standard)

(Pregnancy and infants)

< 5 mcg/dL (US BLL standard)

What are signs and symptoms of....

Acute poisoning (> 80mcg/dL serum lead level)

●

Abdominal pain ("lead colic")

●

Constipation

●

Joint pains

●

Muscle aches

●

Headache

●

Anorexia

●

Decreased libido

●

Difficulty concentrating and deficits in short-term memory

●

Irritability

●

Excessive fatigue

●

Sleep disturbance

●

Confusion, seizures, and encephalopathy can be seen with extremely high levels of lead

●

Anemia

●

Nephropathy (Fanconi-type syndrome)

Chronic exposure (30 to 70mcg/dL)

• can be asymptomatic 

               OR

• myalgias
• fatigue
• irritability
• insomnia
• anorexia
• impaired short-term memory
• difficulty concentrating

More serious health issues ..... 

• Hypertension (Bone lead, a reflection of cumulative lead exposure, was estimated to be an independent risk factor of developing hypertension in Normative Aging Study)
• Mortality and cardiovascular effects (Chronic exposure with low lead levels 20 to 29mcg/dL (0.97 to 1.40 micromol/L), and even less than 10 mcg/dL (0.48 micromol/L) in one report, has been linked to an increase in mortality)
• Neuropsychiatric effects  Encephalopathy may occur and is more common in children. Children with elevated lead concentrations may be asymptomatic apart from intellectual deficits and behavioural disorders.
• Reproductive effects (A)  (Men with chronic lead exposure [and blood lead levels between 40 and 70 mcg/dL (1.93 to 3.38micromol/L) have been found in some studies to have an increased percent of sperm with abnormal morphology and decreased sperm concentration, total sperm count, and total motile sperm count)
•  Reproductive effects (B) Lead readily crosses the placenta. Increased number of miscarriages, stillbirths, and preterm delivery appear to be related to high lead exposures in pregnant women. Reduced birth weight and cognitive impairments also have been reported in babies born to mothers with elevated lead in venous blood, cord blood, or bone.

References: 

• Martindale: The Complete Drug Reference © 2015 The Pharmaceutical Press. MedicinesComplete © 2015 Royal Pharmaceutical Society  https://www.medicinescomplete.com/mc/martindale/current/5298-t.htm?q=lead%20poisoning&t=search&ss=text&p=1#m5298-a5-k
• Uptodate clinical references @2015 http://www.uptodate.com/contents/adult-lead-poisoning?source=machineLearning&search=lead+poisoning&selectedTitle=1~115&sectionRank=3&anchor=H27#H27
• Toxbase (UK clinical toxicology) @2015 https://www.toxbase.org/Poisons-Index-A-Z/L-Products/Lead-Paint/

Summarised by KS Lai @2015