Mass Spectrometry & Spectroscopy
The important role of ICP-MS in understanding the toxicological link between lead contamination and human disease
Robert Thomas, Scientifi c Solutions
Last year (2023) marked the 40th anniversary of the commercialisation of ICP-MS. At the 1983 Pittsburgh Conference, SCIEX introduced the ELAN 250 quadrupole-based ICP Mass Spectrometer. It was another 12 months before its joint venture with PerkinElmer Inc was announced, but the event was the start of the meteoric rise of ICP-MS as the dominant multielement technique used for ultra-trace elemental analysis and the beginning of a competitive race which would see a number of other vendors and other mass spectrometer technologies come and go over the next 40 years. It was also the year that I ‘cut my teeth’ on the technique when I ran the PerkinElmer ICP-MS application/demo lab in the UK.
Today, there are close to 2,000 ICP-MS systems installed worldwide every year, representing around $400 million in annual sales, performing a wide variety of applications, from routine, high-throughput multielement analysis to more complex tasks such as trace element speciation studies with high-performance liquid chromatography and monitoring of nano particles. As more and more laboratories invest in the technique, the list of applications is getting signifi cantly larger and more diverse.
In my recent book on ICP-MS, I have written about the various ICP-MS and atomic spectroscopy (AS) application sectors being carried out by the user community [1]. However, 40 years after the commercialisation of the technique, it would be almost impossible to capture all of them. The most common ones include environmental monitoring, geochemical, metallurgical, petrochemical, food, clinical, toxicology, semiconductor, industrial, energy, agricultural, nuclear, pharmaceuticals, and cannabis consumer products, but every year it seems that a new market has woken up and realised the full potential of the capabilities of ICP-MS.
I am often asked if there was one application area which the technique has made the most important contribution over this time. It’s a very diffi cult question to answer, but if pressed I would have to say it is in the fi eld of human health and safety. Understanding the effects of toxic metals on the human body is as complex as it is fascinating. We know that too low or too high a concentration of essential trace elements in our diet can affect our quality of life. On the other hand, metallic contamination of the air, soil and water supplies can have a dramatic impact on our well-being. There are many examples that highlight both the negative and positive effects of trace metals on our lives. The effect of lead toxicity is well documented, as was demonstrated by the negligence of public health offi cials in Flint, Michigan who didn’t adequately treat the drinking water supply when it changed from Lake Huron to the Flint River and as a result contaminated the water supply with abnormally high levels of lead. The movie Erin Brokovich alarmed us all to the dangers of hexavalent chromium (Cr VI) in drinking water, but how many of the audience realised that trivalent chromium (CRIII) metal is necessary for the metabolism of carbohydrates and fats? A few years ago, Dr Oz, the infamous TV doctor in the US alarmed his viewers about high levels arsenic in apple juice, but what he failed to say was that it was not the highly toxic inorganic form of arsenic, but the arsenic that had been metabolised by the apple tree to the less toxic organic form.
ICP-MS has played a pivotal role in getting a much better understanding of metal toxicity on human health, and without it, we would not have been able to further our knowledge on many of these critical issues. However, there is one application that stands out and that is the dramatic reduction of blood lead levels in young children.
Lead toxicity
Lead has no known biological or physiological purpose in the human body, but is avidly absorbed into the system by ingestion, inhalation and to a lesser extent by skin absorption [2]. Inorganic lead in submicron size particles in particular can be almost completely absorbed through the respiratory tract, whereas larger particles may be swallowed. The extent and rate of absorption of lead through the gastrointestinal tract depend on characteristics of the individual and on the nature of the medium ingested. It has been shown that children can absorb 40-50% of an oral dose of water- soluble lead compared to only 3-10% for adults [3]. Young children are particularly susceptible, because of their playing and eating habits and typically have more hand- to-mouth activity than adults [4]. Lead is absorbed more easily if there is a calcium/
Figure 1: The trend in blood lead levels (µg/dL) in children considered elevated by the Centers for Disease Control and Prevention (CDC), since the mid-1960s
iron defi ciency, or if the child has a high fat, inadequate mineral and/or low protein diet. When absorbed, lead is distributed within the body in three main areas – bones, blood and soft tissue. About 90% is distributed in the bones, while the majority of the rest gets absorbed into the bloodstream where it gets taken up by porphyrin molecules (complex nitrogen-containing organic compounds providing the foundation structure for haemoglobin) in the red blood cells [5]. It is therefore clear that the repercussions and health risks are potentially enormous, if humans (especially young children) have a long-term exposure to high levels of lead.
Health effects
Lead poisoning affects virtually every system in the body, and often occurs with no distinctive symptoms. It can damage the central nervous system, kidneys, and reproductive system and, at higher levels, can cause coma, convulsions, and even death.
Even low levels of lead in children are harmful and are associated with lower intelligence, reduced brain development, decreased growth and impaired hearing [6]. The level of lead in someone’s system is confi rmed by a blood-lead test, which by today’s standards is considered elevated if it is in excess of 3.5 µg/dL (microgram per decilitre).
Note: On 28th October 2021, CDC lowered the blood lead reference value (BLRV) from 5.0 μg/dL to 3.5 μg/dL. A BLRV is intended to identify children with higher levels of lead in their blood compared with levels in most children. The value is based on the 97.5th percentile of the blood lead distribution in U.S. children ages 1-5 years. (for comparison purposes 1 µg/dL = 10 ppb) [7].
INTERNATIONAL LABMATE - APRIL 2024
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68
