Blood lead levels INDEX

Bactericide A pesticide used to control or destroy bacteria Basal diet Ration for adults and starter ration for the young, appropriate to the species it should meet the standard nutritional requirement Base pair mutagens Chemicals or agents that produce a base change in the DNA BEA 2-Bromoethalamine BEI Biological exposure index BLL Blood lead level BEN Balkan endemic nephropathy... 

As noted in Chapters 1 and 2, the committee specifically sought health-effects data on blood lead levels (BLLs) under 40 pg/dL because the current standard of the Occupational Safety and Health Administration (OSHA) aims to maintain BLLs below that concentration. Evidence on health effects at a corresponding estimated cumulative blood lead index (CBLl) of 1,600 pg-years/dL (that is, 40 years at 40 pg/dL) and tibia lead levels of 40-80 pg/g were also specifically sought. 

Studies have shown an association between umbilical blood lead concentration under 10 gg/dL and reduced head circumference (Al-Saleh et al. 2008b), effects on infant attention (Plusquellec et al. 2007), abnormal reflexes and abnormal results on neurologic soft signs scales (Emhart et al. 1986), reduced body-weight gain (Sanin et al. 2001), and decreased body-mass index (NTP 2012). Deficits in visual function in children were also seen at umbihcal blood lead levels as low as 10.5 gg/dL (Rothenberg et al. 2002). Increased maternal... 

Another way to measure lead in the body is via ZINC (or erythrocyte) protoporphyrin (ZPP or EP). This medical marker is not affected by the rebound effect as is the blood lead level. ZPP is an index of the level of lead or iron deficiency or both, as is EP, discussed in Chapter 4 on diagnosing lead poisoning. This index can be useful in indicating... 

The blood lead level is a good index of current or recent lead absorption when there is no anemia present and when the worker has not taken any chelating agents. However, blood lead levels along with urinary lead levels do not necessarily indicate the total body burden of lead and are not adequate measures of past exposure. One reason for this is that lead has a high affinity for bone and up to 90 percent of the body s total lead is deposited there. A very important component of the total lead body burden is lead in soft tissue (liver, kidney, and brain). This fraction of the lead body burden, the biologically active lead, is not entirely reflected by blood lead levels since it is a function of the dynamics of lead absorption, distribu-... 

There are several ways one can quantify human health risk characterization for humans at risk through lead exposure. The first and simplest examines the prevalences or incidences of blood lead levels above some health risk threshold, with frequencies of exceedance identifying those at more risk (compared to those with PbB values below the risk threshold). Expressions of health risk in terms of elevated PbB occurrences (e.g., 10 jig/dl) do not simultaneously provide quantitative estimates of organ- or system-specific toxic harm, such as actual loss of IQ points or increases in SBP or DBP. A health risk threshold indexed in terms of a PbB level, however, represents the synthesis of numerous empirical dose—toxic response relationships, as developed and discussed in previous chapters. 

These studies employed blood-lead levels as an index of exposure. Other workers have used hair-lead and tooth-lead, with generally similar results. 

To assess the association between prenatal/early postnatal lead exposure and development, we followed a group of urban US infants from birth to 2 years of age. Estimates of the association between lead and Bayley Mental Development Index (MDI) scores at ages 6, 12, 18, and 24 months were obtained using several regression options. In all multivariate models examined, MDI scores were associated with umbilical cord blood lead levels, but not with postnatal blood lead levels. Infants with high cord blood lead levels (10-25 jUg/dl) consistently scored 4 to 8 points lower than infants with low cord blood lead levels (< 3 jUg/dl). Infants vulnerability to lead s developmental toxicity appears to be greatest during the fetal period. 

Results from several cohort studies are now available. Bellinger et al (1986) failed to find any relation, for middle-class infants, of 6-month and 12-month blood lead levels (PbB) and the Mental Development Index (MDI) of the Bayley Scales of Infant Development. Dietrich et al. (in press) reported a significant relationship of 3-month, but not 6-month, PbB with 6-month MDI... 

One of the problems highlighted in recent times is the importance of fiber in the diet. Normal starch is rapidly broken down into simple sugars by enzymes (amylases) in the human body. A high consumption of starch can lead to spikes in blood sugar level. The rate and extent of this rise are measured by the glycemic index. To avoid sharp fluctuations, which are thought to be damaging to health, inclusion of a certain amount of fiber in the diet is recommended. 

The measurement of total N02 and N03 in blood is an index of endothelial nitric oxide synthase activity (TessaroUo et al., 2015). Moreover, the high altitude subjects suffer from the reduction of N02 level in their blood, leading to several diseases at hypoxia conditions (Kim et al., 2003). Recent studies reported that the administration of N03 -rich beetroot juice to human and several animal models promotes NO-like... 

In summary, the use of shed dentition as a biological indicator of cumulative exposure to lead in children would appear to be appropriate under certain conditions. These conditions include rigorous steps to minimize variance in the measure multiple tooth sampling restricted to the same type (and location if possible), or use of concordance criteria for acceptance or rejection of lead levels in replicate sampling. By its nature, measurement of lead in teeth is a retrospective index of exposure to lead, and this measure is not as inherently useful for regulatory policy or clinical intervention/management of lead exposure and intoxication as is PbB. The various prospective studies currently under way in different countries for lead exposure/effects in children include some that utilize serial measurement of PbB in the paediatric subjects as they develop. Comparison of these multiple measurements with lead in shed dentition in the future would be valuable in establishing blood lead-tooth lead relationships. 

There is a continuing need to estimate body burdens of lead in order to monitor exposure levels. In order to relate lead levels to neurobehavioural outcomes, the critical index is the amount of lead to which the brain has been exposed. Since exposures at different ages and developmental stages may have different outcomes, the ideal measure would be something that reflected the lead level in the brain at a critical point in time. Such a measure is not available, so researchers have used blood, shed deciduous teeth, or hair, as indicators of body lead burden. All these provide an imperfect estimate, but the question is which is the best measure under which circumstances To add to the complications, it is possible that different estimates of body lead may relate to different outcomes. Hair has generally not proved to be a suitable measure, so the choice is between blood, or some blood constituent such as A-LAD or protoporphyrin, or shed teeth. 

OSHA has set a standard to keep blood levels in the occupational work force below 40 //g/dL. ACGIH has set a goal relating to a biological exposure index of 50 //g/dL for lead in blood and 150 pjgjdL creatinine for lead in urine. 

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